Recent Postings from Special Topics

The bird's ear view of space physics: Audification as a tool for the spectral analysis of time series data

Alexander, R. L., S. O'Modhrain, D. A. Roberts, J. A. Gilbert, and T. H. Zurbuchen (2014), The bird's ear view of space physics: Audification as a tool for the spectral analysis of time series data, J. Geophys. Res. Space Physics, 119, 5259–5271, doi:10.1002/2014JA020025.

The effective navigation, mining, and analysis of large time series data sets presents a recurring challenge throughout heliophysics. Audification, a specific form of auditory analysis commonly used in other fields of research (such as geoseismology), provides a promising technique for the evaluation of spectral features in long heliospheric time series data sets. Following a standard research methodology for the development of new analysis techniques, this paper presents a detailed case study in which audification was introduced into the working process of an experienced heliophysics research scientist and used for the identification and classification of features in high-resolution magnetometer data during a structured analysis task. Auditory evaluation successfully led to the detection of artificial, instrument-induced noise that was not previously observed by the scientist and also the identification of wave activity embedded within turbulent solar wind data. A follow-up interview indicated that the scientist continued using these auditory analysis methods in the assessment of every large data set during the 2 months after the study was completed. These findings indicate that audification can be valuable and enabling for researchers in forming a deeper understanding of both microstructures and macrostructures within large time series. Additionally, as both a standalone methodology and a supplement to visual analysis methods, audification can expedite certain stages of the data survey, analysis, and mining process and provide new qualitative insight into the spectral content of time-varying signals.

Long-Term Prospects: Mitigation of Supernova and Gamma-Ray Burst Threat to Intelligent Beings

We consider global catastrophic risks due to cosmic explosions (supernovae, magnetars and gamma-ray bursts) and possible mitigation strategies by humans and other hypothetical intelligent beings. While by their very nature these events are so huge to daunt conventional thinking on mitigation and response, we wish to argue that advanced technological civilizations would be able to develop efficient responses in the domain of astroengineering within their home planetary systems. In particular, we suggest that construction of shielding swarms of small objects/particles confined by electromagnetic fields could be one way of mitigating the risk of cosmic explosions and corresponding ionizing radiation surges. Such feats of astroengineering could, in principle, be detectable from afar by advanced Dysonian SETI searches.

Comments: Accepted for publication in Acta Astronautica. 21 pages, 1 figure, 1 table

Timescales for the Penetration of IMF By into the Earth's Magnetotail

Browett S.D., R.C Fear, A. Grocott, and S.E. Milan (2016), Timescales for the Penetration of IMF By into the Earth's Magnetotail, J. Geophys. Res., 121, doi:10.1002/2016JA023198.

Previous studies have shown there is a correlation between the By component of the interplanetary magnetic field (IMF) and the By component observed in the magnetotail lobe and in the plasma sheet. However, studies of the effect of IMF By on several magnetospheric processes have indicated that the By component in the tail should depend more strongly on the recent history of the IMF By rather than on the simultaneous measurements of the IMF. Estimates of this timescale vary from ∼15 minutes to ∼4 hours. We present a statistical study of how promptly the IMF By component is transferred into the neutral sheet, based on Cluster observations of the neutral sheet from 2001 to 2008, and solar wind data from the OMNI database. 5982 neutral sheet crossings during this interval were identified, and starting with the correlation between instantaneous measurements of the IMF and the magnetotail (recently reported by Cao et al. [2014]), we vary the time delay applied to the solar wind data. Our results suggest a bimodal distribution with peaks at ∼1.5 and ∼3 hours. The relative strength of each peak appears to be well controlled by: the sign of the IMF Bz component with peaks being observed at 1 hour of lag time for southward IMF and up to 5 hours for northward IMF conditions, and the magnitude of the solar wind velocity with peaks at 2 hours of lag time for fast solar wind and 4 hours for slow solar wind conditions.

The Holometer: An Instrument to Probe Planckian Quantum Geometry

Aaron Chou, Henry Glass, H. Richard Gustafson, Craig Hogan, Brittany L. Kamai, Ohkyung Kwon, Robert Lanza, Lee McCuller, Stephan S. Meyer, Jonathan Richardson, Chris Stoughton, Ray Tomlin, Rainer Weiss

This paper describes the Fermilab Holometer, an instrument for measuring correlations of position variations over a four-dimensional volume of space-time. The apparatus consists of two co-located, but independent and isolated, 40m power-recycled Michelson interferometers, whose outputs are cross-correlated to 25 MHz. The data are sensitive to correlations of differential position across the apparatus over a broad band of frequencies up to and exceeding the inverse light crossing time, 7.6 MHz. A noise model constrained by diagnostic and environmental data distinguishes among physical origins of measured correlations, and is used to verify shot-noise-limited performance. These features allow searches for exotic quantum correlations that depart from classical trajectories at spacelike separations, with a strain noise power spectral density sensitivity smaller than the Planck time. The Holometer in current and future configurations is projected to provide precision tests of a wide class of models of quantum geometry at the Planck scale, beyond those already constrained by currently operating gravitational wave observatories.

Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum

A vacuum test campaign evaluating the impulsive thrust performance of a tapered radio-frequency test article excited in the transverse magnitude 212 mode at 1937 MHz has been completed. The test campaign consisted of a forward thrust phase and reverse thrust phase at less than 8×10−6 torr vacuum with power scans at 40, 60, and 80 W. The test campaign included a null thrust test effort to identify any mundane sources of impulsive thrust; however, none were identified. Thrust data from forward, reverse, and null suggested that the system was consistently performing with a thrust-to-power ratio of 1.2±0.1 mN/kW1.2±0.1  mN/kW.

Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum

The magnetic field and turbulence of the cosmic web measured using a brilliant fast radio burst

Fast radio bursts (FRBs) are millisecond-duration events thought to originate beyond the Milky Way galaxy. Uncertainty surrounding the burst sources, and their propagation through intervening plasma, has limited their use as cosmological probes. We report on a mildly dispersed (dispersion measure 266.5 ± 0.1 pc cm−3), exceptionally intense (120 ± 30 Jy), linearly polarized, scintillating burst (FRB 150807) that we directly localize to 9 arcmin2. Based on a low Faraday rotation (12.0 ± 0.7 rad m−2), we infer negligible magnetization in the circum-burst plasma and constrain the net magnetization of the cosmic web along this sightline to < 21 nG, parallel to the line-of-sight. The burst scintillation suggests weak turbulence in the ionized intergalactic medium.

Dan Rather: "Now more than ever we must stand up for science"

"The Trump administration is outlining policies that put our response to climate change in deep jeopardy and threaten to change the fundamental direction of science in the U.S."

A sequence of flux transfer events potentially generated by different generation mechanisms

Trenchi, L., R. C. Fear, K. J. Trattner, B. Mihaljcic, and A. N. Fazakerley (2016), A sequence of flux transfer events potentially generated by different generation mechanisms, J. Geophys. Res. Space Physics, 121, 8624–8639, doi:10.1002/2016JA022847.

Flux transfer events (FTEs) are magnetic structures generated by time-varying reconnection at the dayside magnetopause. Understanding their generation mechanism is important, because it is necessary in order to understand the global contribution of FTEs to the convection process. We present observations of several FTEs sequentially observed by Cluster at the subsolar magnetopause. Cluster detected also several reconnection jets, which seem to be systematically associated with the trailing edge of the FTEs. This association is expected only in the FTEs formed by single X line reconnection but could be compatible also with the multiple X line model, when reconnection at one X line is dominant. Instead, it does not seem compatible with original mechanism proposed by Russell and Elphic (1978). For a large FTE, not associated with any reconnection jet, the Grad-Shafranov reconstruction obtained from Cluster 1 data recovers a flux rope, indicative of multiple X line reconnection. This same FTE was detected also by Cluster 3, which observed an asymmetric signature in the magnetic field component normal to the magnetopause. We show that this asymmetric signature was caused by an outward motion of the magnetopause. The orientation of the other FTEs, obtained from a Grad-Shafranov optimization, shows considerable spread, despite the relatively steady conditions. Our interpretation is that a combination of single and multiple X line reconnection generated these FTEs. The FTEs in the first part of the crossing, associated with reconnection jets, are generated by the single X line model and may therefore not satisfy the Grad-Shafranov assumptions so well. Instead, the last FTE, slower, bigger, and well separated from the previous ones, may be formed by multiple X line reconnection.

A triple protostar system formed via fragmentation of a gravitationally unstable disk

Binary and multiple star systems are a frequent outcome of the star formation process and as a result almost half of all stars with masses similar to that of the Sun have at least one companion star. Theoretical studies indicate that there are two main pathways that can operate concurrently to form binary/multiple star systems: large-scale fragmentation of turbulent gas cores and filaments or smaller-scale fragmentation of a massive protostellar disk due to gravitational instability. Observational evidence for turbulent fragmentation on scales of more than 1,000 astronomical units has recently emerged. Previous evidence for disk fragmentation was limited to inferences based on the separations of more-evolved pre-main sequence and protostellar multiple systems. The triple protostar system L1448 IRS3B is an ideal system with which to search for evidence of disk fragmentation as it is in an early phase of the star formation process, it is likely to be less than 150,000 years old and all of the protostars in the system are separated by less than 200 astronomical units. Here we report observations of dust and molecular gas emission that reveal a disk with a spiral structure surrounding the three protostars. Two protostars near the centre of the disk are separated by 61 astronomical units and a tertiary protostar is coincident with a spiral arm in the outer disk at a separation of 183 astronomical units. The inferred mass of the central pair of protostellar objects is approximately one solar mass, while the disk surrounding the three protostars has a total mass of around 0.30 solar masses. The tertiary protostar itself has a minimum mass of about 0.085 solar masses. We demonstrate that the disk around L1448 IRS3B appears susceptible to disk fragmentation at radii between 150 and 320 astronomical units, overlapping with the location of the tertiary protostar. This is consistent with models for a protostellar disk that has recently undergone gravitational instability, spawning one or two companion stars.

Lightning as a space-weather hazard: UK thunderstorm activity modulated by the passage of the heliospheric current sheet

Owens, M. J., C. J. Scott, A. J. Bennett, S. R. Thomas, M. Lockwood, R. G. Harrison, and M. M. Lam (2015), Lightning as a space-weather hazard: UK thunderstorm activity modulated by the passage of the heliospheric current sheet, Geophys. Res. Lett., 42, 9624–9632, doi:10.1002/2015GL066802.

Lightning flash rates, RL, are modulated by corotating interaction regions (CIRs) and the polarity of the heliospheric magnetic field (HMF) in near-Earth space. As the HMF polarity reverses at the heliospheric current sheet (HCS), typically within a CIR, these phenomena are likely related. In this study, RL is found to be significantly enhanced at the HCS and at 27 days prior/after. The strength of the enhancement depends on the polarity of the HMF reversal at the HCS. Near-Earth solar and galactic energetic particle fluxes are also ordered by HMF polarity, though the variations qualitatively differ from RL, with the main increase occurring prior to the HCS crossing. Thus, the CIR effect on lightning is either the result of compression/amplification of the HMF (and its subsequent interaction with the terrestrial system) or that energetic particle preconditioning of the Earth system prior to the HMF polarity change is central to solar wind lightning coupling mechanism.

Good Enough Practices in Scientific Computing

Greg WilsonJennifer BryanKaren CranstonJustin KitzesLex NederbragtTracy K. Teal

We present a set of computing tools and techniques that every researcher can and should adopt. These recommendations synthesize inspiration from our own work, from the experiences of the thousands of people who have taken part in Software Carpentry and Data Carpentry workshops over the past six years, and from a variety of other guides. Our recommendations are aimed specifically at people who are new to research computing.

Impacts into quartz sand: Crater formation, shock metamorphism, and ejecta distribution in laboratory experiments and numerical models

Abstract–We investigated the ejection mechanics by a complementary approach of cratering
experiments, including the microscopic analysis of material sampled from these experiments,
and 2-D numerical modeling of vertical impacts. The study is based on cratering
experiments in quartz sand targets performed at the NASA Ames Vertical Gun Range. In
these experiments, the preimpact location in the target and the final position of ejecta was
determined by using color-coded sand and a catcher system for the ejecta. The results were
compared with numerical simulations of the cratering and ejection process to validate the
iSALE shock physics code. In turn the models provide further details on the ejection
velocities and angles. We quantify the general assumption that ejecta thickness decreases
with distance according to a power-law and that the relative proportion of shocked material
in the ejecta increase with distance. We distinguish three types of shock metamorphic
particles (1) melt particles, (2) shock lithified aggregates, and (3) shock-comminuted grains.
The agreement between experiment and model was excellent, which provides confidence that
the models can predict ejection angles, velocities, and the degree of shock loading of
material expelled from a crater accurately if impact parameters such as impact velocity,
impactor size, and gravity are varied beyond the experimental limitations. This study is
relevant for a quantitative assessment of impact gardening on planetary surfaces and the
evolution of regolith layers on atmosphereless bodies.

Paper link

First measurement of surface nuclear recoil background for argon dark matter searches

Jingke Xu, Chris Stanford, Shawn Westerdale, Frank Calaprice, Alexander Wright, Zhiming Shi

One major background in direct searches for weakly interacting massive particles (WIMPs) comes from the deposition of radon progeny on detector surfaces. The most dangerous surface background is the 206Pb recoils produced by 210Po decays. In this letter, we report the first characterization of this background in liquid argon. The scintillation signal of low energy Pb recoils is measured to be highly quenched in argon, and we estimate that the 103keV 206Pb recoil background will produce a signal equal to that of a ~5keV (30keV) electron recoil (40Ar recoil). In addition, we demonstrate that this dangerous 210Po surface background can be suppressed by a factor of ~100 or higher using pulse shape discrimination methods, which can make argon dark matter detectors near background-free and enhance their potential for discovery of medium- and high-mass WIMPs. We also discuss the impact on other low background experiments.

abstract    pdf


Recent positron excess data from AMS-02

Presentation at TeVPA 2016 showing a time dependence to the positron excess related to the solar magnetic field reversal.

slides pdf


Speaking with Rockstar's soundtrack supervisor

Speaking with Rockstar's soundtrack supervisor, Ivan Pavlovich, the interview covers things like obtaining the services of DJ Pooh, who acquired samples from top name rappers like Snoop Dogg and Dr.Dre, names that are probably very popular amongst the potsmoking groupies of the 1990s.There's also celebrities like Pam Grier, Bootsy Collins and Kenny Loggins contributing to various forms of different music cultures present throughout GTA V that appeals to the different vibes and counties of Los Santos and the larger region of San Andreas.

All together, there are 15 different radio stations each championing to the appeal of different tastes in music and music culture.In simple terms, there's at least going to be a little bit of something in there for everyone.The game has already garnered tons of excitement, especially with the GTA Online mode and the ability to create your own gangs although, the video showcasing the games was hit with a ceasedesist so there's nothing to link back to.

Given that there isn't much else to say about GTA V at this point and I can't embed anything that probably wouldn't result in TakeTwo's lawyers knocking on the door of Cinema Blend's owner, I'll instead Runescape Gold talk about Hill Bill yes, that little iOS game Hill Bill.This sidescrolling title released not too long ago to very little fanfare but has received quite the response from customers, with 24's Jack Bauer writing on the iTunes page that it's a.

Sublimation as a landform-shaping process on pluto

Using each class's unique weapons effectively

The D.A.G.E.R.System reviewed the Wii U version of the game and noted that the Gamepad is a blessing and curse due to its ability to make platforming easier with the touchpad, but the lack of control customization proved to be a feature that could make it difficult to use for some disabled gamers.Rayman Legends also managed to score high marks for its visuals and audio, getting the Barrier Free ranks since gamers who are color blind wouldn't run into problems and the same was said of the audio features as well.

Both The Bureau: XCOM Declassified and Rayman Legends are available right now for home consoles and PC.Game Refuge has announced that they're developing General Chaos 2: Sons of Chaos, sequel to their Sega Genesis strategy game.They've launched a Kickstarter campaign in an effort to raise enough money to complete the project.General Chaos was a mix of realtime tactics and action.Players lead a squad of soldiers against an opposing forces.The five character classes of the soldiers ranged from the flamethrowerwielding Scorchers to the grenadetossing Chuckers.

Using each class's unique weapons effectively was the key to victory.When two enemies entered close range, they'd have to duke it out in a short brawl.The game supported fourplayer Runescape Gold cooperative play as well as headtohead matches.Chaos might be one of the best games I remember from my Genesis days.It was really ahead of its time.Fourplayer coop and character classes were both a rarity in the action genre back then.

You don't just watch the latest Hellraid traileryou play it

You don't just watch the latest Hellraid traileryou play it.Techland has released an interactive trailer for the firstperson hackandslash game.The video is entitled "Edyn's Escape" and is set two weeks RS Gold before the events of Hellraid's campaign.The player character is Edyn, a monk whose monastery has been attacked by the forces of Hell.Players guide him as he flees to safety."Edyn's Escape" is structured as a chooseyourownadventure story.

You make your way through the monastery and are presented with a series of thisorthat choices.Will you go right or left.Take the swordandshield or the axe.For the most part, picking the "wrong" option leads to your bloody demise.Some of these deaths are pretty cheap.About a minute into the video, I was blown up about by a chest I opened up.Those old Choose Your Own Adventure books prepared me well for sudden and undeserved death, though.

Fortunately, you can just hit "back" on your browser to redo your choices instead of restarting the whole video.If you survive the adventure, you'll be given a special reward.If you'd rather just have the reward, go here.It's an MP3 of "Siege of Hell," one of the songs from the Hellraid soundtrack.In Hellraid, the mortal realm has been overrun by Hell's minions.Players take on the role of a Paladin, Rogue, Barbarian, or Mage attempting to fight back this invasion.

For fastpaced competitive firstperson shooter titles

For fastpaced competitive firstperson shooter titles and simulation racing games that require 1:1 response timing, I don't think this iMotion will cut it.But hey, that's just my observation.Anyway, the device is aimed to work with any webcam and can easily be picked up thanks to its easytoread LEDs.On the upside, I can see this being a useful Runescape Gold device to work in conjunction with the Oculus Rift or maybe work as a great companion device with the OmniTreadmill, handling things like duck, jump and activate or melee attacks while standard movement is handled by the treadmill and the Oculus Rift handles looking around.

Dang, that would be one kickbutt combination of gaming gear.I don't know how the iMotion will really work out if it really fills a void that isn't already capable of being filled by a blue tooth dongle and a Wiimote, but if gamers, modders and designers can come up with a way to use the iMotion haptic controller for games in ways that isn't already available such as for fighting games or using motionbased spell casting in MMOs and RPGs then all the more power to them.

If you like what Intelligent Motion is selling with the iMotion, feel free to support the project by paying a visit to the official Kickstarter page.The players of Dungeons and Dragons MMO Neverwinter are currently spread across three servers, or "shards." However, Cryptic Studios says they'll be making a server upgrade in "the very near future" to merge these three shards into one.The merge sounds like it should be a smooth process.You won't have to worry about changing your character's name so it won't conflict with a character from another servers, due to the unique handle on each account.

The habitability of Proxima Centauri b

I. Irradiation, rotation and volatile inventory from formation to the present

II. Possible climates and observability

A terrestrial planet candidate in a temperate orbit around Proxima Centauri

At a distance of 1.295 parsecs1, the red dwarf Proxima Centauri (α Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun’s closest stellar neighbour and one of the best-studied low-mass stars. It has an effective temperature of only around 3,050 kelvin, a luminosity of 0.15 per cent of that of the Sun, a measured radius of 14 per cent of the radius of the Sun2 and a mass of about 12 per cent of the mass of the Sun. Although Proxima is considered a moderately active star, its rotation period is about 83 days (ref. 3) and its quiescent activity levels and X-ray luminosity4 are comparable to those of the Sun. Here we report observations that reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units. Its equilibrium temperature is within the range where water could be liquid on its surface5.

The PAN-STARRS1 Distant z>5.6 QUASAR Survey

Probing more than 100 QUASARS within the first Gyr of the Universe

Liquid-filled canyons on Titan

Joule heating hot spot at high latitudes in the afternoon sector

Cai, L., A. T. Aikio, and S. E. Milan (2016), Joule heating hot spot at high latitudes in the afternoon sector, J. Geophys. Res. Space Physics, 121, doi:10.1002/2016JA022432.

The afternoon Joule heating hot spot has been studied statistically by using the EISCAT Svalbard Radar (ESR) measurements at 75.4° Corrected Geomagnetic latitude (CGMLAT) and the OMNI solar wind data base. For a small subset of events, the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) field-aligned current distributions have been available. The main results are as follows. Afternoon Joule heating hot spots are associated with high values of ionospheric electric fields and slightly enhanced Pedersen conductances. The Joule heating hot spot values are larger in summer than in winter, which can be explained by the higher Pedersen conductances during summer than winter. The afternoon Joule heating hot spots are located close to the reversals of the large-scale field-aligned current systems. The most common location is close to the Region 1/Region 2 boundary and those events are associated with sunward convecting F region plasma. In a few cases, the hot spots take place close to the Region 1/Region 0 boundary and then the ionospheric plasma is convecting antisunward. The hot spots may occur both during slow (450 km/s) speed solar wind conditions. During slow-speed solar wind events, the dominant interplanetary magnetic field (IMF) direction is southward, which is the general requirement for the low-latitude magnetic merging at the dayside magnetopause. During high-speed solar wind, also northward IMF conditions appear, but those are associated with large values of the IMF |By| component, making again the dayside magnetopause merging possible. Finally, the measured afternoon hot spot Joule heating rates are not a linear function of the solar wind energy coupling function.

Rural tech startups see success across the US

While tech startups have become synonymous with urban areas that offer improved access to talent, resources and infrastructure, the reality is that rural areas are also home to startups.

This may come as a surprise to those who have moved away from rural areas specifically to find a job in the tech industry, which accounts for more than 6.7 million jobs in the United States alone. Population loss is a real issue for much of rural America; some states, such as Nebraska and Kansas, have introduced tax incentives to fight back against this trend. Others are turning to technology to counter the trend.

States are starting to recognize the importance of supporting and developing opportunities for rural counties. In the state of Washington, the Department of Commerce has been encouraging business plan competitions in rural areas with “at least 10 competitions in rural areas that we have promoted and supported,” stated Maury Forman, senior manager of the rural initiatives and innovations at Washington State Department of Commerce.

This foresight is necessary to support tech startups and the entrepreneurs behind them — tech startups tend to grow quickly in their early years, which offsets “job destruction from early-stage business failures,” which in turn leads to a more robust job market.

Live. Give. Save. Inc., is a financial tech startup based in the city of Red Wing, Minnesota, home to a little over 16,000 people. “Red Wing has a history of pioneers … and inventors. There’s a rich, rich beautiful history of arts, culture and innovation,” said Susan Sorensen Langer, CEO, Live. Give. Save., Inc., a financial tech startup that is creating a mobile platform to boost retirement savings through charitable giving.

Langer moved out to Red Wing after her contract ended with her last employer and was introduced to Neela Mollgaard, Executive Director of Red Wing Ignite, a nonprofit organization that develops and promotes next-generation technology services and applications. “I was blown away by what they were doing in Red Wing,” Langer said, and spoke to the desire to change Red Wing’s image into a place that would become known for startups much like Austin, Texas.

Support from the community to provide the necessary resources and infrastructure has been invaluable to the success of tech startups such as Live. Give. Save., Inc. In 2012, the city of Red Wing and Hiawatha Broadband Communications (HBC) formed a public-private partnership to bring gigabit broadband to Red Wing. For entrepreneurs such as Langer, who have virtual teams, having access to fast internet is crucial.

While other rural areas may not have the same support Red Wing has, technological updates and developments have been on the rise. Certain companies have specifically focused on bringing broadband internet to rural America. “I am often asked if the difficulty of running a company in a rural area is high-speed internet. It’s not,” said Ken Levy, CEO and co-founder of 4-Tell, which helps increase sales for online retailers by 17.1 percent with big data.

C. Skyler Young, owner of Site Savvy, a tech startup that provides managed websites and online marketing for small to mid-sized businesses based in Yakima, Washington, has a similar experience to Levy. “Access to internet hasn’t really been an issue actually,” said Young. “There are a few dead zones in town; some of the communication infrastructure dates back to the 20s,” Young said. “However, it’s been updated a great deal in recent years. It’s not at all hard to find good connections these days.”

While Yakima has a larger population that what is typically considered to be rural, the land is undeveloped and used mostly for agricultural purposes. Known to locals as the little sister of Seattle, Yakima offers plenty of opportunities to enjoy the outdoors, with mountains and bodies of water surrounding the area.

In terms of access to talent, Levy has credited the Columbia River Gorge area with attracting “a personality type that is perfect for startups, and employees want to move here.” Levy stated that “the Gorge has created a high-tech hub with over a thousand technical employees centered around Insitu (a division of Boeing) and related software and hardware companies.”

While both Young and Langer spoke about the difficulties they’ve faced in getting talent to move to rural areas, they credit remote employees and having a virtual team as filling this gap. “After this [product] kickoff, what I plan is to get a couple of developers to move to Red Wing,” Langer said. Young noted that although finding talent was still a struggle, “it’s becoming easier as time goes on … as people work remotely and choose to live more comfortable and sustainable lifestyles in the countryside.”

And the advantages to having your tech startup based in a rural area? Plenty. Young was full of praise, citing “low cost of living, no traffic, elbow room, and easy access to the outdoors.” In a similar vein, Langer talked about how Red Wing is a great place for those with a love of the outdoors, its close proximity to both Minneapolis and St. Paul, as well as only being 45 minutes away from the nearest airport. “Red Wing is the perfect mix of small town and big city,” Langer said. “It’s a wonderful place to raise children. It’s got everything.” An important factor Levy brought up was access to quality education. The Gorge has access to quality schools and “employees for a high-tech company want the best schools for their kids.”

Although challenges still exist for rural startups, the assumption that rural areas cannot support tech startups is coming under fire. Because of the initiatives of state organizations and private companies, as well as the opening of co-working spaces, rural areas are being given the attention they need and deserve to develop and invest in opportunities that will allow business as a whole to grow and succeed.

The physiology and habitat of the last universal common ancestor

The physiology and habitat of the last universal common ancestor
Madeline C. Weiss, Filipa L. Sousa, Natalia Mrnjavac, Sinje Neukirchen, Mayo Roettger, Shijulal Nelson-Sathi & William F. Martin
Nature Microbiology 1, 16116 (2016)

The concept of a last universal common ancestor of all cells (LUCA, or the progenote) is central to the study of early evolution and life's origin, yet information about how and where LUCA lived is lacking. We investigated all clusters and phylogenetic trees for 6.1 million protein coding genes from sequenced prokaryotic genomes in order to reconstruct the microbial ecology of LUCA. Among 286,514 protein clusters, we identified 355 protein families (∼0.1%) that trace to LUCA by phylogenetic criteria. Because these proteins are not universally distributed, they can shed light on LUCA's physiology. Their functions, properties and prosthetic groups depict LUCA as anaerobic, CO2-fixing, H2-dependent with a Wood–Ljungdahl pathway, N2-fixing and thermophilic. LUCA's biochemistry was replete with FeS clusters and radical reaction mechanisms. Its cofactors reveal dependence upon transition metals, flavins, S-adenosyl methionine, coenzyme A, ferredoxin, molybdopterin, corrins and selenium. Its genetic code required nucleoside modifications and S-adenosyl methionine-dependent methylations. The 355 phylogenies identify clostridia and methanogens, whose modern lifestyles resemble that of LUCA, as basal among their respective domains. LUCA inhabited a geochemically active environment rich in H2, CO2 and iron. The data support the theory of an autotrophic origin of life involving the Wood–Ljungdahl pathway in a hydrothermal setting.

NYT: Meet Luca, the Ancestor of All Living Things

LUX Results from IDM

Twitter post of the money plot:

Link to full presenation:

Nature Comment: "Let's make peer review scientific"

The quiescent intracluster medium in the core of the Perseus cluster

Hitomi Collaboration, Nature 535, 117–121 (07 July 2016)

Clusters of galaxies are the most massive gravitationally bound objects in the Universe and are still forming. They are thus important probes1 of cosmological parameters and many astrophysical processes. However, knowledge of the dynamics of the pervasive hot gas, the mass of which is much larger than the combined mass of all the stars in the cluster, is lacking. Such knowledge would enable insights into the injection of mechanical energy by the central supermassive black hole and the use of hydrostatic equilibrium for determining cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50-million-kelvin diffuse hot plasma filling its gravitational potential well. The active galactic nucleus of the central galaxy NGC 1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These bubbles probably induce motions in the intracluster medium and heat the inner gas, preventing runaway radiative cooling—a process known as active galactic nucleus feedback2, 3, 4, 5, 6. Here we report X-ray observations of the core of the Perseus cluster, which reveal a remarkably quiescent atmosphere in which the gas has a line-of-sight velocity dispersion of 164 ± 10 kilometres per second in the region 30–60 kiloparsecs from the central nucleus. A gradient in the line-of-sight velocity of 150 ± 70 kilometres per second is found across the 60-kiloparsec image of the cluster core. Turbulent pressure support in the gas is four per cent of the thermodynamic pressure, with large-scale shear at most doubling this estimate. We infer that a total cluster mass determined from hydrostatic equilibrium in a central region would require little correction for turbulent pressure.

Journal Club - 7/6/16

Two papers to discuss for this week's journal club

Evolution and Persistence of Students' Astronomy Career Interests

I'll be presenting this paper during MSU Astro Coffee on June 22, 2016:

GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence

GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence

We report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. Subsequent off-line analyses recovered GW151226 with a network signal-to-noise ratio of 13 and a significance greater than 5σ. The signal persisted in the LIGO frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 Hz, and reached a peak gravitational strain of 3.4+0.7−0.9×10−22. The inferred source-frame initial black hole masses are 14.2+8.3−3.7M⊙ and 7.5+2.3−2.3M⊙, and the final black hole mass is 20.8+6.1−1.7M⊙. We find that at least one of the component black holes has spin greater than 0.2. This source is located at a luminosity distance of 440+180−190  Mpc corresponding to a redshift of 0.09+0.03−0.04. All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.

B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration)
Phys. Rev. Lett. 116, 241103 – Published 15 June 2016

See also

Binary Black Hole Mergers in the first Advanced LIGO Observing Run

The first observational run of the Advanced LIGO detectors, from September 12, 2015 to January 19, 2016, saw the first detections of gravitational waves from binary black hole mergers. In this paper we present full results from a search for binary black hole merger signals with total masses up to 100 M☉ and detailed implications from our observations of these systems. Our search, based on general-relativistic models of gravitational wave signals from binary black hole systems, unambiguously identified two signals, GW150914 and GW151226, with a significance of greater than 5σ over the observing period. It also identified a third possible signal, LVT151012, with substantially lower significance, which has a 87% probability of being of astrophysical origin. We provide detailed estimates of the parameters of the observed systems. Both GW150914 and GW151226 provide an unprecedented opportunity to study the two-body motion of a compact-object binary in the large velocity, highly nonlinear regime. We do not observe any deviations from general relativity, and place improved empirical bounds on several high-order post-Newtonian coefficients. From our observations we infer stellar-mass binary black hole merger rates lying in the range 9–240 Gpc^−3 yr^−1. These observations are beginning to inform astrophysical predictions of binary black hole formation rates, and indicate that future observing runs of the Advanced detector network will yield many more gravitational wave detections.

Associated Press Releases:

LIGO Press Release: LIGO Does It Again: A Second Robust Binary Black Hole Coalescence Observed

MIT Press Release: For second time, LIGO detects gravitational waves

Science Press Release: LIGO detects another black hole crash

Journal Club Discussion

This week we are going to have a discussion about Journal Club. What works and what doesn't? What would you like to see in the future? Is there a time/location that would be preferable for the future? All thoughts and ideas are welcome!

LISA Pathfinder results

Physics: Invest in neutrino astronomy

Spencer Klein calls for bigger telescope arrays to catch particles from the most energetic places in the Universe.

Tsunami waves extensively resurfaced the shorelines of an early Martian ocean

Geophysical controls of chemical disequilibria in Europa

The hot γ Doradus and Maia stars

The hot γ Doradus stars have multiple low frequencies characteristic of γ Dor or SPB variables, but are located between the red edge of the SPB and the blue edge of the γ Dor instability strips where all low-frequency modes are stable in current models of these stars. Though δ Sct stars also have low frequencies, there is no sign of high frequencies in hot γ Dor stars. We obtained spectra to refine the locations of some of these stars in the H-R diagram and conclude that these are, indeed, anomalous pulsating stars. The Maia variables have multiple high frequencies characteristic of β Cep and δ Sct stars, but lie between the red edge of the β Cep and the blue edge of the δ Sct instability strips. We compile a list of all Maia candidates and obtain spectra of two of these stars. Again, it seems likely that these are anomalous pulsating stars which are currently not understood.

Reduction in field-aligned currents preceding and local to auroral substorm onset

Murphy, K. R., I. R. Mann, I. J. Rae, C. L. Waters, B. J. Anderson, D. K. Milling, H. J. Singer, and H. Korth (2012), Reduction in field-aligned currents preceding and local to auroral substorm onset, Geophys. Res. Lett., 39, L15106, doi:10.1029/2012GL052798.

We examine the global field-aligned current (FAC) topology associated with a clear substorm on the 16 February 2010. We show that for this particular substorm there is a clear and localised reduction in the FACs observed by AMPERE at least 6 minutes prior to auroral onset. A new auroral arc forms in the region of reduced FAC and on closed field lines which subsequently brightens and expands poleward, signifying the start of the substorm expansion phase. We argue that the change in FACs observed prior to onset is the result of a change in the magnetosphere-ionosphere (M-I) coupling in a region local to the subsequent auroral onset. Such a change implies an important role for M-I coupling in destabilising the near-Earth tail during magnetospheric substorms and perhaps more importantly in selecting the location in the ionosphere where auroral onset begins.

Observation of the 60Fe nucleosynthesis-clock isotope in galactic cosmic rays

W. R. Binns1,*, M. H. Israel1,*, E. R. Christian2, A. C. Cummings3, G. A. de Nolfo2, K. A. Lave1, R. A. Leske3, R. A. Mewaldt3, E. C. Stone3, T. T. von Rosenvinge2, M. E. Wiedenbeck4

60Fe is a radioactive isotope in cosmic rays that serves as a clock to infer an upper limit on the time between nucleosynthesis and acceleration. We have used the ACE-CRIS instrument to collect 3.55 × 105 iron nuclei, with energies ~195 to ~500 MeV/nucleon, of which we identify 15 60Fe nuclei. The 60Fe/56Fe source ratio is (7.5 ± 2.9) × 10−5. The detection of supernova-produced 60Fe in cosmic rays implies that the time required for acceleration and transport to Earth does not greatly exceed the 60Fe half-life of 2.6 Myr and that the 60Fe source distance does not greatly exceed the distance cosmic rays can diffuse over this time, ⪍ 1 kpc. A natural place for 60Fe origin is in nearby clusters of massive stars.

Resolved atomic lines reveal outflows in two ultraluminous X-ray sources

Resolved atomic lines reveal outflows in two ultraluminous X-ray sources. Pinto et al. 2016, Nature

Ultraluminous X-ray sources are extragalactic, off-nucleus, point sources in galaxies, and have X-ray luminosities in excess of 3 × 1039 ergs per second. They are thought to be powered by accretion onto a compact object. Possible explanations include accretion onto neutron stars with strong magnetic fields1, onto stellar-mass black holes (of up to 20 solar masses) at or in excess of the classical Eddington limit2, 3, 4, or onto intermediate-mass black holes (103–105 solar masses)5. The lack of sufficient energy resolution in previous analyses has prevented an unambiguous identification of any emission or absorption lines in the X-ray band, thereby precluding a detailed analysis of the accretion flow6, 7, 8. Here we report the presence of X-ray emission lines arising from highly ionized iron, oxygen and neon with a cumulative significance in excess of five standard deviations, together with blueshifted (about 0.2 times light velocity) absorption lines of similar significance, in the high-resolution X-ray spectra of the ultraluminous X-ray sources NGC 1313 X-1 and NGC 5408 X-1. The blueshifted absorption lines must occur in a fast-outflowing gas, whereas the emission lines originate in slow-moving gas around the source. We conclude that the compact object in each source is surrounded by powerful winds with an outflow velocity of about 0.2 times that of light, as predicted by models of accreting supermassive black holes and hyper-accreting stellar-mass black holes9, 10.


No pressure: NSF test finds eliminating deadlines halves number of grant proposals

Eliminating deadlines halves number of grant proposals

ScienceInsider, Eric Hand, Apr. 15, 2016

In recent years, the National Science Foundation (NSF) has struggled with the logistics of evaluating a rising number of grant proposals that has propelled funding rates to historic lows. Annual or semiannual grant deadlines lead to enormous spikes in submissions, which in turn cause headaches for the program managers who have to organize merit review panels. Now, one piece of the agency has found a potentially powerful new tool to flatten the spikes and cut the number of proposals: It can simply eliminate deadlines.

[...] the preliminary results from a pilot program that got rid of grant proposal deadlines in favor of an anytime submission. The numbers were staggering. Across four grant programs, proposals dropped by 59% after deadlines were eliminated.

Interstellar 60Fe on the Surface of the Moon

L. Fimiani, D. L. Cook, T. Faestermann, J. M. Gómez-Guzmán, K. Hain, G. Herzog, K. Knie, G. Korschinek, P. Ludwig, J. Park, R. C. Reedy, and G. Rugel
Phys. Rev. Lett. 116, 151104

A dying massive star ends in a supernova explosion ejecting a large fraction of its mass into the interstellar medium. If this happens nearby, part of the ejecta might end on Solar System bodies and, in fact, radioactive Fe60 has been detected on the Pacific ocean floor in about 2 Ma old layers. Here, we report on the detection of this isotope also in lunar samples, originating presumably from the same event. The concentration of the cosmic ray produced isotope Mn53, measured in the same samples, proves the supernova origin of the Fe60. From the Fe60 concentrations found we deduce a reliable value for the local interstellar fluence in the range of 1×108  at/cm2. Thus, we obtain constraints on the recent and nearby supernova(e).

Synopsis here:

The locations of recent supernovae near the Sun from modelling 60Fe transport

D. Brietschwerdt, J. Feige, M.M. Schulreich, M.A. de Avillez, C. Dettbarn, & B. Fuchs

Nature 532, 73–76 (07 April 2016)

The signature of 60Fe in deep-sea crusts indicates that one or more supernovae exploded in the solar neighbourhood about 2.2 million years ago1, 2, 3, 4. Recent isotopic analysis is consistent with a core-collapse or electron-capture supernova that occurred 60 to 130 parsecs from the Sun5. Moreover, peculiarities in the cosmic ray spectrum point to a nearby supernova about two million years ago6. The Local Bubble of hot, diffuse plasma, in which the Solar System is embedded, originated from 14 to 20 supernovae within a moving group, whose surviving members are now in the Scorpius–Centaurus stellar association7, 8. Here we report calculations of the most probable trajectories and masses of the supernova progenitors, and hence their explosion times and sites. The 60Fe signal arises from two supernovae at distances between 90 and 100 parsecs. The closest occurred 2.3 million years ago at present-day galactic coordinates l = 327°, b = 11°, and the second-closest exploded about 1.5 million years ago at l = 343°, b  = 25°, with masses of 9.2 and 8.8 times the solar mass, respectively. The remaining supernovae, which formed the Local Bubble, contribute to a smaller extent because they happened at larger distances and longer ago (60Fe has a half-life of 2.6 million years9, 10). There are uncertainties relating to the nucleosynthesis yields and the loss of 60Fe during transport, but they do not influence the relative distribution of 60Fe in the crust layers, and therefore our model reproduces the measured relative abundances very well.

Recent near-Earth supernovae probed by global deposition of interstellar radioactive 60Fe

Wallner, A., et al.  Nature 532, 69–72 (07 April 2016)

The rate of supernovae in our local Galactic neighbourhood within a distance of about 100 parsecs from Earth is estimated to be one every 2–4 million years, based on the total rate in the Milky Way (2.0 ± 0.7 per century1, 2). Recent massive-star and supernova activity in Earth’s vicinity may be traced by radionuclides with half-lives of up to 100 million years3, 4, 5, 6, if trapped in interstellar dust grains that penetrate the Solar System. One such radionuclide is 60Fe (with a half-life of 2.6 million years)7, 8, which is ejected in supernova explosions and winds from massive stars1, 2, 9. Here we report that the 60Fe signal observed previously in deep-sea crusts10, 11 is global, extended in time and of interstellar origin from multiple events. We analysed deep-sea archives from all major oceans for 60Fe deposition via the accretion of interstellar dust particles. Our results reveal 60Fe interstellar influxes onto Earth at 1.5–3.2 million years ago and at 6.5–8.7 million years ago. The signal measured implies that a few per cent of fresh 60Fe was captured in dust and deposited on Earth. Our findings indicate multiple supernova and massive-star events during the last ten million years at distances of up to 100 parsecs.

A white dwarf with an oxygen atmosphere

Contribution of Antarctica to past and future sea-level rise

Contribution of Antarctica to past and future sea-level rise
Robert M. DeConto & David Pollard
Nature, 531, 591–597 (31 March 2016)

Polar temperatures over the last several million years have, at times, been slightly warmer than today, yet global mean sea level has been 6–9 metres higher as recently as the Last Interglacial (130,000 to 115,000 years ago) and possibly higher during the Pliocene epoch (about three million years ago). In both cases the Antarctic ice sheet has been implicated as the primary contributor, hinting at its future vulnerability. Here we use a model coupling ice sheet and climate dynamics—including previously underappreciated processes linking atmospheric warming with hydrofracturing of buttressing ice shelves and structural collapse of marine-terminating ice cliffs that is calibrated against Pliocene and Last Interglacial sea-level estimates and applied to future greenhouse gas emission scenarios. Antarctica has the potential to contribute more than a metre of sea-level rise by 2100 and more than 15 metres by 2500, if emissions continue unabated. In this case atmospheric warming will soon become the dominant driver of ice loss, but prolonged ocean warming will delay its recovery for thousands of years.

Acceleration of petaelectronvolt protons in the Galactic Centre

HESS Collaboration

Galactic cosmic rays reach energies of at least a few petaelectronvolts (of the order of 1015electronvolts). This implies that our Galaxy contains petaelectronvolt accelerators (‘PeVatrons’), but all proposed models of Galactic cosmic-ray accelerators encounter difficulties at exactly these energies. Dozens of Galactic accelerators capable of accelerating particles to energies of tens of teraelectronvolts (of the order of 1013 electronvolts) were inferred from recent γ-ray observations. However, none of the currently known accelerators—not even the handful of shell-type supernova remnants commonly believed to supply most Galactic cosmic rays—has shown the characteristic tracers of petaelectronvolt particles, namely, power-law spectra of γ-rays extending without a cut-off or a spectral break to tens of teraelectronvolts. Here we report deep γ-ray observations with arcminute angular resolution of the region surrounding the Galactic Centre, which show the expected tracer of the presence of petaelectronvolt protons within the central 10 parsecs of the Galaxy. We propose that the supermassive black hole Sagittarius A* is linked to this PeVatron. Sagittarius A* went through active phases in the past, as demonstrated by X-ray outbursts and an outflow from the Galactic Centre . Although its current rate of particle acceleration is not sufficient to provide a substantial contribution to Galactic cosmic rays, Sagittarius A* could have plausibly been more active over the last 106–107 years, and therefore should be considered as a viable alternative to supernova remnants as a source of petaelectronvolt Galactic cosmic rays.

cosINUs Cryogenic NaI and CsI scintillators

Instrumentation papers from cosINUs for CRESST style CsI and NaI detectors.

Electron density enhancements in the polar cap during periods of dayside reconnection

Clausen, L. B. N., and J. I. Moen (2015), Electron density enhancements in the polar cap during periods of dayside reconnection. J. Geophys. Res. Space Physics, 120, 4452–4464. doi: 10.1002/2015JA021188.

Using field-aligned current data, we monitor the location of the region 1 current oval which is related to the location of the polar cap boundary (PCB). We identify intervals when the current oval and hence the PCB moved equatorward for extended periods lasting at least 75 min, and we term these intervals sustained dayside reconnection events (SDRE). We find 1059 SDREs between 2010 and 2012 and go on to study the dynamics of the total electron content (TEC) in the high-latitude region in a superposed epoch sense. Immediately after the beginning of a SDRE, a plasma density increase forms at the poleward edge of the PCB and its edge moves from the location of the dayside PCB antisunward at speeds of about 500 m/s, consistent with ionospheric convection measurements. Our results show that the TEC inside the polar cap locally increases by up to 20%. Averaged over the entire polar region poleward of 55∘ magnetic latitude, however, we find no significant increase in the TEC, indicating that local increases and decreases are formed by transport and rearrangement of existing plasma rather than by impact ionization due to particle precipitation. We also observe a latitudinally narrow region between the TEC increases equatorward and poleward of the dayside PCB in which the TEC stagnates. This stagnation trough may be due to local flow channels associated with bursty dayside reconnection.

Radio brightening of FRB 150418 host galaxy candidate

A repeating fast radio burst

Computation in the Classroom

For MSU's astro coffee meeting on March 1, 2016, I'm planning on presenting some information about bringing programming and computation into the classroom by highlighting some work by physics education researchers at MSU.  Specifically, I'll use the following to articles to help guide the discussion:

"Computation across the curriculum: What skills are needed?" (


"A Case Study: Novel Group Interactions through Introductory Computational Physics" (

Positron annihilation signatures associated with the outburst of the microquasar V404 Cygni (Nature)

Siegert et al. 2016, Nature

Link to paper behind paywall

Microquasars1234 are stellar-mass black holes accreting matter from a companion star5 and ejecting plasma jets at almost the speed of light. They are analogues of quasars that contain supermassive black holes of 106 to 1010 solar masses. Accretion in microquasars varies on much shorter timescales than in quasars and occasionally produces exceptionally bright X-ray flares6. How the flares are produced is unclear, as is the mechanism for launching the relativistic jets and their composition. An emission line near 511 kiloelectronvolts has long been sought in the emission spectrum of microquasars as evidence for the expected electron–positron plasma. Transient high-energy spectral features have been reported in two objects78, but their positron interpretation9remains contentious. Here we report observations of γ-ray emission from the microquasar V404 Cygni during a recent period of strong flaring activity10. The emission spectrum around 511 kiloelectronvolts shows clear signatures of variable positron annihilation, which implies a high rate of positron production. This supports the earlier conjecture that microquasars may be the main sources of the electron–positron plasma responsible for the bright diffuse emission of annihilation γ-rays in the bulge region of our Galaxy11. Additionally, microquasars could be the origin of the observed megaelectronvolt continuum excess in the inner Galaxy.

Radio brightening of FRB 150418 host galaxy candidate

The host galaxy of a fast radio burst

If light waves are stretched by gravitational waves, how can we use light as a ruler to detect gravitational waves?

A bit of background related to the LIGO gravitational wave detection.

From AIP:


or the same article on ADS:

Seas Are Rising at Fastest Rate in Last 28 Centuries

Temperature-driven global sea-level variability in the Common Era
Kopp et al. 2016
Proceedings of the National Academy of Sciences
(Direct PDF link)

We present the first estimate of global sea-level (GSL) change over the last ∼3000 years that is based upon statistical synthesis of a global database of regional sea-level reconstructions. [...] The 20th century rise was extremely likely faster than during any of the 27 previous centuries. Semiempirical modeling indicates that, without global warming, GSL in the 20th century very likely would have risen by between −3 cm and +7 cm, rather than the ∼14 cm observed. Semiempirical 21st century projections largely reconcile differences between Intergovernmental Panel on Climate Change projections and semiempirical models.

Commentary: The Human Fingerprints on Coastal Floods
For the 20th century, Kopp and his colleagues’ central estimate is global sea level has risen about four-and-a-half inches. Extended through 2014 for our follow-on report, the estimate increases to six inches. These don’t sound like world-changing numbers, especially considering that many sea level projections for the this century run beyond three feet. But if you live in Annapolis or Charleston, Atlantic City or Port Isabel, our analysis shows that those inches have already changed your world.

NYTimes article: Seas Are Rising at Fastest Rate in Last 28 Centuries.

Observation of Gravitational Waves from a Binary Black Hole Merger

Observation of Gravitational Waves from a Binary Black Hole Merger

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 × 10-21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410+160-180 Mpc corresponding to a redshift z = 0.09+0.03−0.04. In the source frame, the initial black hole masses are 36+5-4 M☉ and 29+4-4 M☉, and the final black hole mass is 62+4-4 M☉, with 3.0+0.5-0.5 M☉c2 radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

See also the list of related documents:

LIGO-P1500229: Observing gravitational-wave transient GW150914 with minimal assumptions
LIGO-P1500269: GW150914: First results from the search for binary black hole coalescence with Advanced LIGO
LIGO-P1500218: Properties of the binary black hole merger GW150914
LIGO-P1500217: The Rate of Binary Black Hole Mergers Inferred from Advanced LIGO Observations Surrounding GW150914
LIGO-P1500262: Astrophysical Implications of the Binary Black-Hole Merger GW150914
LIGO-P1500213: Tests of general relativity with GW150914
LIGO-P1500222: GW150914: Implications for the stochastic gravitational-wave background from binary black holes
LIGO-P1500248: Calibration of the Advanced LIGO detectors for the discovery of the binary black-hole merger GW150914
LIGO-P1500238: Characterization of transient noise in Advanced LIGO relevant to gravitational wave signal GW150914
LIGO-P1500271: High-energy Neutrino follow-up search of Gravitational Wave Event GW150914 with IceCube and ANTARES
LIGO-P1500237: GW150914: The Advanced LIGO Detectors in the Era of First Discoveries

Oxygen isotopic evidence for vigorous mixing during the Moon-forming giant impact

Edward D. Young, Issaku E. Kohl, Paul H. Warren, David C. Rubie, Seth A. Jacobson, and Alessandro Morbidelli

Science  29 Jan 2016:
Vol. 351, Issue 6272, pp. 493-496
DOI: 10.1126/science.aad0525

Earth and the Moon are shown here to have indistinguishable oxygen isotope ratios, with a difference in Δ′17O of −1 ± 5 parts per million (2 standard error). On the basis of these data and our new planet formation simulations that include a realistic model for primordial oxygen isotopic reservoirs, our results favor vigorous mixing during the giant impact and therefore a high-energy, high-angular-momentum impact. The results indicate that the late veneer impactors had an average Δ′17O within approximately 1 per mil of the terrestrial value, limiting possible sources for this late addition of mass to the Earth-Moon system.


Going, going, ...

Mastering the game of Go with deep neural networks and tree search
David Silver et al.,
Nature, 529, 484–489 (28 January 2016)

The game of Go has long been viewed as the most challenging of classic games for artificial intelligence owing to its enormous search space and the difficulty of evaluating board positions and moves. Here we introduce a new approach to computer Go that uses ‘value networks’ to evaluate board positions and ‘policy networks’ to select moves. These deep neural networks are trained by a novel combination of supervised learning from human expert games, and reinforcement learning from games of self-play. Without any lookahead search, the neural networks play Go at the level of state-of-the-art Monte Carlo tree search programs that simulate thousands of random games of self-play. We also introduce a new search algorithm that combines Monte Carlo simulation with value and policy networks. Using this search algorithm, our program AlphaGo achieved a 99.8% winning rate against other Go programs, and defeated the human European Go champion by 5 games to 0. This is the first time that a computer program has defeated a human professional player in the full-sized game of Go, a feat previously thought to be at least a decade away.

See also: Blog post at Google Research.

Interhemispheric differences in ionospheric convection: Cluster EDI observations revisited

Förster, M., and S. Haaland (2015), Interhemispheric differences in ionospheric convection: Cluster EDI observations revisited, J. Geophys. Res. Space Physics, 120, 5805–5823, doi:10.1002/2014JA020774.

The interaction between the interplanetary magnetic field and the geomagnetic field sets up a large-scale circulation in the magnetosphere. This circulation is also reflected in the magnetically connected ionosphere. In this paper, we present a study of ionospheric convection based on Cluster Electron Drift Instrument (EDI) satellite measurements covering both hemispheres and obtained over a full solar cycle. The results from this study show that average flow patterns and polar cap potentials for a given orientation of the interplanetary magnetic field can be very different in the two hemispheres. In particular during southward directed interplanetary magnetic field conditions, and thus enhanced energy input from the solar wind, the measurements show that the southern polar cap has a higher cross polar cap potential. There are persistent north-south asymmetries, which cannot easily be explained by the influence of external drivers. These persistent asymmetries are primarily a result of the significant differences in the strength and configuration of the geomagnetic field between the Northern and Southern Hemispheres. Since the ionosphere is magnetically connected to the magnetosphere, this difference will also be reflected in the magnetosphere in the form of different feedback from the two hemispheres. Consequently, local ionospheric conditions and the geomagnetic field configuration are important for north-south asymmetries in large regions of geospace.

ASASSN-15lh: A highly super-luminous supernova

Subo Dong; B. J. Shape; J. L. Prieto and others

Science article


We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as the most luminous supernova yet found. At redshift z = 0.2326, ASASSN-15lh reached an absolute magnitude of Mu,AB = –23.5 ± 0.1 and bolometric luminosity Lbol = (2.2 ± 0.2) × 1045 ergs s–1, which is more than twice as luminous as any previously known supernova. It has several major features characteristic of the hydrogen-poor super-luminous supernovae (SLSNe-I), whose energy sources and progenitors are currently poorly understood. In contrast to most previously known SLSNe-I that reside in star-forming dwarf galaxies, ASASSN-15lh appears to be hosted by a luminous galaxy (MK ≈ –25.5) with little star formation. In the 4 months since first detection, ASASSN-15lh radiated (1.1 ± 0.2) × 1052 ergs, challenging the magnetar model for its engine.



Evidence for a Distant Giant Planet in the Solar System


Konstantin Batygin and Michael E. Brown


Recent analyses have shown that distant orbits within the scattered disk population of the Kuiper Belt exhibit an unexpected clustering in their respective arguments of perihelion. While several hypotheses have been put forward to explain this alignment, to date, a theoretical model that can successfully account for the observations remains elusive. In this work we show that the orbits of distant Kuiper Belt objects (KBOs) cluster not only in argument of perihelion, but also in physical space. We demonstrate that the perihelion positions and orbital planes of the objects are tightly confined and that such a clustering has only a probability of 0.007% to be due to chance, thus requiring a dynamical origin. We find that the observed orbital alignment can be maintained by a distant eccentric planet with mass gsim10 m whose orbit lies in approximately the same plane as those of the distant KBOs, but whose perihelion is 180° away from the perihelia of the minor bodies. In addition to accounting for the observed orbital alignment, the existence of such a planet naturally explains the presence of high-perihelion Sedna-like objects, as well as the known collection of high semimajor axis objects with inclinations between 60° and 150° whose origin was previously unclear. Continued analysis of both distant and highly inclined outer solar system objects provides the opportunity for testing our hypothesis as well as further constraining the orbital elements and mass of the distant planet.

Link to popular press diagram:

Detection of a SN near the center of the galaxy cluster field MACS1149 consistent with predictions of a new image of Supernova Refsdal

In Hubble Space Telescope (HST) WFC3-IR exposures taken on UT 2015 December 10 (GO-14199; PI: Kelly), we discovered a new transient source in the MACS J1149.6+2223 (Ebeling et al. 2003) galaxy cluster field.

The new source was not detected in WFC3-IR exposures taken during a previous visit to the field on UT 2015 October 30.8 nor in earlier imaging from the FrontierSN program (GO-13790; PI: Rodney), Frontier Fields (GO/DD-13504; PI: Lotz), or Grism Lens-Amplified Survey from Space (GLASS, GO-14095; PI: Treu) programs. The new image is marginally detected in data taken in November 2015.

This new image coincides with a multiply imaged background galaxy at z = 1.49. This same galaxy, but seen as a different image, is the host galaxy of SN Refsdal, a SN discovered in November 2014 as four separate images in an Einstein cross configuration around an early-type cluster member (Kelly et al. 2015). Multiple lensing models consistently predicted that SN Refsdal would re-appear, within several years, at the position of the other image of the host galaxy closer to the galaxy center (Kelly et al. 2015 [using Zitrin et al. 2009]; see also Oguri et al. 2015; Sharon & Johnson 2015; Diego et al. 2015; Jauzac et al. 2015; Treu et al. 2015). The new SN, which we denote as 'SX,' is significantly fainter than images S1-S3 of the SN Refsdal Einstein cross when they were discovered in images taken on UT 2014 November 10.

The new SN position is both approximately spatially and temporally coincident with predictions for the location and timing of the delayed image of SN Refsdal. Moreover, the brightness differences are also approximately consistent with relative magnification predictions.

We conclude that this new SN is likely the re-appearance of SN Refsdal.

Hawaiian court revokes permit for Thirty Meter Telescope

Decision throws construction of the Thirty Meter Telescope into question.

Hawaii's supreme court has ruled that the construction permit for the Thirty Meter Telescope (TMT) atop the mountain of Mauna Kea is invalid. The 2 December decision is a major blow to the international consortium backing the US$1.5-billion telescope, and a win for the Native Hawaiians who have protested its construction on what they regard as a sacred summit.

Court decision here:

Ducks in space

A subcritical pattern-forming system with nonlinear advection in a bounded domain is recast as a slow-fast system in space and studied using a combination of geometric singular perturbation theory and numerical continuation. Two types of solutions describing the possible location of stationary fronts are identified, one of which is present for all values of the bifurcation parameter while the other is present for zero or sufficiently small inlet boundary conditions but only when the bifurcation parameter is large enough. For slightly larger inlet boundary condition a continuous transition from one type to the other takes place as the bifurcation parameter increases. The origin of the two solution types is traced to the onset of convective and absolute instability on the real line. The role of canard trajectories in the transitions between these states is clarified and the stability properties of the resulting spatial structures are determined. Front location in the convective regime is highly sensitive to the upstream boundary condition and its dependence on this boundary condition is studied using a combination of numerical continuation and Monte Carlo simulations of the partial differential equation. Statistical properties of the system subjected to random or stochastic boundary conditions are interpreted using the deterministic slow-fast spatial-dynamical system.

An extremely bright gamma-ray pulsar in the Large Magellanic Cloud

Pulsars are rapidly spinning, highly magnetized neutron stars, created in the gravitational collapse of massive stars. We report the detection of pulsed giga–electron volt gamma rays from the young pulsar PSR J0540–6919 in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. This is the first gamma-ray pulsar detected in another galaxy. It has the most luminous pulsed gamma-ray emission yet observed, exceeding the Crab pulsar’s by a factor of 20. PSR J0540–6919 presents an extreme test case for understanding the structure and evolution of neutron star magnetospheres.

Science 13 November 2015

A small nearby star with an Earth-like planet

A rocky planet transiting a nearby low-mass star
Zachory K. Berta-Thompson et al.,
Nature, 527, 204–207 (12 November 2015); doi:10.1038/nature15762

M-dwarf stars — hydrogen-burning stars that are smaller than 60 per cent of the size of the Sun — are the most common class of star in our Galaxy and outnumber Sun-like stars by a ratio of 12:1. Recent results have shown that M dwarfs host Earth-sized planets in great numbers: the average number of M-dwarf planets that are between 0.5 to 1.5 times the size of Earth is at least 1.4 per star. The nearest such planets known to transit their star are 39 parsecs away, too distant for detailed follow-up observations to measure the planetary masses or to study their atmospheres. Here we report observations of GJ 1132b, a planet with a size of 1.2 Earth radii that is transiting a small star 12 parsecs away. Our Doppler mass measurement of GJ 1132b yields a density consistent with an Earth-like bulk composition, similar to the compositions of the six known exoplanets with masses less than six times that of the Earth and precisely measured densities. Receiving 19 times more stellar radiation than the Earth, the planet is too hot to be habitable but is cool enough to support a substantial atmosphere, one that has probably been considerably depleted of hydrogen. Because the host star is nearby and only 21% the radius of the Sun, existing and upcoming telescopes will be able to observe the composition and dynamics of the planetary atmosphere.

News and Views discussion by Drake Deming.


Link to ApJ paper

Scaling relations between central black hole (BH) mass and host galaxy properties are of fundamental importance to studies of BH and galaxy evolution throughout cosmic time. Here we investigate the relationship between BH mass and host galaxy total stellar mass using a sample of 262 broad-line active galactic nuclei (AGNs) in the nearby universe (z < 0.055), as well as 79 galaxies with dynamical BH masses. The vast majority of our AGN sample is constructed using Sloan Digital Sky Survey spectroscopy and searching for Seyfert-like narrow-line ratios and broad Hα emission. BH masses are estimated using standard virial techniques. We also include a small number of dwarf galaxies with total stellar masses Mstellar lesssim 109.5 M⊙ and a subsample of the reverberation-mapped AGNs. Total stellar masses of all 341 galaxies are calculated in the most consistent manner feasible using color-dependent mass-to-light ratios. We find a clear correlation between BH mass and total stellar mass for the AGN host galaxies, with MBH ∝ Mstellar, similar to that of early-type galaxies with dynamically detected BHs. However, the relation defined by the AGNs has a normalization that is lower by more than an order of magnitude, with a BH-to-total stellar mass fraction of MBH/Mstellar ~ 0.025% across the stellar mass range 108 ≤ Mstellar/M⊙ ≤ 1012. This result has significant implications for studies at high redshift and cosmological simulations in which stellar bulges cannot be resolved.

[1510.07561] A local non-negative initial data scalar characterisation of the Kerr solution

For any vacuum initial data set, we define a local, non-negative scalar quantity which vanishes at every point of the data hypersurface if and only if the data are {\em Kerr initial} data. Our scalar quantity only depends on the quantities used to construct the vacuum initial data set which are the Riemannian metric defined on the initial data hypersurface and a symmetric tensor which plays the role of the second fundamental form of the embedded initial data hypersurface. The dependency is {\em algorithmic} in the sense that given the initial data one can compute the scalar quantity by algebraic and differential manipulations, being thus suitable for an implementation in a numerical code. The scalar could also be useful in studies of the non-linear stability of the Kerr solution because it serves to measure the deviation of a vacuum initial data set from the Kerr initial data in a local and algorithmic way.

[arXiv:1510.07561] [PDF]

Quantum physics: Death by experiment for local realism

Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres
Hensen et al.,
Nature (2015); doi:10.1038/nature15759

More than 50 years ago, John Bell proved that no theory of nature that obeys locality and realism can reproduce all the predictions of quantum theory: in any local-realist theory, the correlations between outcomes of measurements on distant particles satisfy an inequality that can be violated if the particles are entangled. Numerous Bell inequality tests have been reported; however, all experiments reported so far required additional assumptions to obtain a contradiction with local realism, resulting in 'loopholes'. Here we report a Bell experiment that is free of any such additional assumption and thus directly tests the principles underlying Bell’s inequality. [...] Our data imply statistically significant rejection of the local-realist null hypothesis.

News and Views discussion - with a useful illustration of the experimental setup.

Authors' site with links to media coverage etc.

Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon

Evidence for carbon cycling or biologic activity can be derived from carbon isotopes, because a high12C/13C ratio is characteristic of biogenic carbon due to the large isotopic fractionation associated with enzymatic carbon fixation. The earliest materials measured for carbon isotopes at 3.8 Ga are isotopically light, and thus potentially biogenic. Because Earth’s known rock record extends only to ∼4 Ga, earlier periods of history are accessible only through mineral grains deposited in later sediments. We report 12C/13C of graphite preserved in 4.1-Ga zircon. Its complete encasement in crack-free, undisturbed zircon demonstrates that it is not contamination from more recent geologic processes. Its12C-rich isotopic signature may be evidence for the origin of life on Earth by 4.1 Ga.

The rise of fully turbulent flow. Barkley et al., Nature

Link to the paper.

Link to comment on the paper (news & views).

Over a century of research into the origin of turbulence in wall-bounded shear flows has resulted in a puzzling picture in which turbulence appears in a variety of different states competing with laminar background flow123456. At moderate flow speeds, turbulence is confined to localized patches; it is only at higher speeds that the entire flow becomes turbulent. The origin of the different states encountered during this transition, the front dynamics of the turbulent regions and the transformation to full turbulence have yet to be explained. By combining experiments, theory and computer simulations, here we uncover a bifurcation scenario that explains the transformation to fully turbulent pipe flow and describe the front dynamics of the different states encountered in the process. Key to resolving this problem is the interpretation of the flow as a bistable system with nonlinear propagation (advection) of turbulent fronts. These findings bridge the gap between our understanding of the onset of turbulence7 and fully turbulent flows89.

Periodic impact cratering and extinction events over the last 260 million years

The claims of periodicity in impact cratering and biological extinction events are controversial. A newly revised record of dated impact craters has been analyzed for periodicity, and compared with the record of extinctions over the past 260 Myr. A digital circular spectral analysis of 37 crater ages (ranging in age from 15 to 254 Myr ago) yielded evidence for a significant 25.8 ± 0.6 Myr cycle. Using the same method, we found a significant 27.0 ± 0.7 Myr cycle in the dates of the eight recognized marine extinction events over the same period. The cycles detected in impacts and extinctions have a similar phase. The impact crater dataset shows 11 apparent peaks in the last 260 Myr, at least 5 of which correlate closely with significant extinction peaks. These results suggest that the hypothesis of periodic impacts and extinction events is still viable.

Published in MNRAS online October 20, 2015

MNRAS (2015) 454 (4): 3480-3484. doi:10.1093/mnras/stv2088

Double Images from a Single Black Hole [arXiv:1510.03530]

In the simulations of the multi-black holes and merging black holes a larger primary image and a secondary smaller image which looks like an eyebrow and the deformation of the shadows have been observed. However, this kind of eyebrow-like structure was considered as unique feature of multi black hole systems. In this paper, we illustrate the new result that in the case of octupole distortions of a Schwarzschild black hole the local observer sees two shadows or two images for this single black hole, i.e., also an eyebrow-like structure. Presence of two images in our case is remarkable, as we have only one black hole, however, the observer sees two dark images of this single black hole.

[arXiv:1510.03530] [PDF]

VLA Reveals Spectacular "Halos" of Spiral Galaxies

Constraining scalar-tensor theories of gravity from the most massive neutron stars 1510.03471

In the news: "Famous Berkeley Astronomer Violated Sexual Harassment Policies Over Many Years"

Although in our journal clubs we often discuss more positive ways that astronomy shows up in the news, we should also not shy from talking about ways in which our community can do better.  A few days ago, it came to light that Geoff Marcy, one of the most well-known people in the world in the field of exoplanets, has a long history of sexual harassment of students.  A few resources are:

Optomechanical test of the Schrödinger-Newton equation

The Schr\"odinger-Newton equation has been proposed as an experimentally testable alternative to quantum gravity, accessible at low energies. It contains self-gravitational terms, which slightly modify the quantum dynamics. Here we show that it distorts the spectrum of a harmonic system. Based on this effect, we propose an optomechanical experiment with a trapped microdisc to test the Schr\"odinger-Newton equation, and we show that it can be realized with existing technology.

arXiv:1510.01696 [PDF]

LISA path finder

A Perfect Bounce

We study the quantum cosmology of a universe with conformal matter comprising a perfect radiation fluid and a number of conformally coupled scalar fields. For FRW backgrounds, we are able to perform the quantum gravity path integral exactly. We find the evolution to describe a “perfect bounce,” in which the universe passes smoothly through the singularity. The Feynman path integral amplitude is precisely that of a relativistic oscillator, for which the scale factor of the universe is the time and the scalar fields are the spatial coordinates. This picture provides natural, unitary quantum mechanical evolution across a bounce. We also study the quantum evolution of anisotropies and of inhomogeneous perturbations, at linear and nonlinear order. We provide evidence for a semiclassical description in which all fields pass “around” the cosmological singularity along complex classical paths.

Gravitational waves from binary supermassive black holes missing in pulsar observations

Science 25 September 2015:
Vol. 349 no. 6255 pp. 1522-1525
DOI: 10.1126/science.aab1910


Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems would modulate the arrival times of pulses from radio pulsars. Using observations of millisecond pulsars obtained with the Parkes radio telescope, we constrained the characteristic amplitude of this background, Ac,yr, to be <1.0 × 10−15 with 95% confidence. This limit excludes predicted ranges for Ac,yr from current models with 91 to 99.7% probability. We conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments and that higher-cadence and shorter-wavelength observations would be more sensitive to gravitational waves.

Astrosat Launches

The formation of submillimetre-bright galaxies from gas infall over a billion years. Narayanan et al. 2015, Nature

Link for the paper.

Submillimetre-bright galaxies at high redshift are the most luminous, heavily star-forming galaxies in the Universe and are characterized by prodigious emission in the far-infrared, with a flux of at least five millijanskys at a wavelength of 850 micrometres. They reside in haloes with masses about 1013 times that of the Sun, have low gas fractions compared to main-sequence disks at a comparable redshift, trace complex environments and are not easily observable at optical wavelengths. Their physical origin remains unclear. Simulations have been able to form galaxies with the requisite luminosities, but have otherwise been unable to simultaneously match the stellar masses, star formation rates, gas fractions and environments. Here we report a cosmological hydrodynamic galaxy formation simulation that is able to form a submillimetre galaxy that simultaneously satisfies the broad range of observed physical constraints. We find that groups of galaxies residing in massive dark matter haloes have increasing rates of star formation that peak at collective rates of about 500–1,000 solar masses per year at redshifts of two to three, by which time the interstellar medium is sufficiently enriched with metals that the region may be observed as a submillimetre-selected system. The intense star formation rates are fuelled in part by the infall of a reservoir gas supply enabled by stellar feedback at earlier times, not through major mergers. With a lifetime of nearly a billion years, our simulations show that the submillimetre-bright phase of high-redshift galaxies is prolonged and associated with significant mass buildup in early-Universe proto-clusters, and that many submillimetre-bright galaxies are composed of numerous unresolved components (for which there is some observational evidence11).

Advanced LIGO to Begin Operations

Relativistic boost as the cause of periodicity in a massive black-hole binary candidate

Relativistic boost as the cause of periodicity in a massive black-hole binary candidate
Daniel J. D'Orazio, Zoltán Haiman & David Schiminovich
Nature 525, 351–353 (17 September 2015)

Because most large galaxies contain a central black hole, and galaxies often merge, black-hole binaries are expected to be common in galactic nuclei. Although they cannot be imaged, periodicities in the light curves of quasars have been interpreted as evidence for binaries, most recently in PG 1302-102, which has a short rest-frame optical period of four years. If the orbital period of the black-hole binary matches this value, then for the range of estimated black-hole masses, the components would be separated by 0.007–0.017 parsecs, implying relativistic orbital speeds. There has been much debate over whether black-hole orbits could be smaller than one parsec. Here we report that the amplitude and the sinusoid-like shape of the variability of the light curve of PG 1302-102 can be fitted by relativistic Doppler boosting of emission from a compact, steadily accreting, unequal-mass binary. We predict that brightness variations in the ultraviolet light curve track those in the optical, but with a two to three times larger amplitude. This prediction is relatively insensitive to the details of the emission process, and is consistent with archival ultraviolet data. Follow-up ultraviolet and optical observations in the next few years can further test this prediction and confirm the existence of a binary black hole in the relativistic regime.

Enceladus’s measured physical libration requires a global subsurface ocean

Enceladus’s measured physical libration requires a global subsurface ocean
P.C. Thomas, R. Tajeddine, M.S. Tiscareno, J.A. Burns, J. Joseph, T.J. Loredo, P. Helfenstein, C. Porco
Icarus, 2015 08 037

Several planetary satellites apparently have subsurface seas that are of great interest for, among other reasons, their possible habitability. The geologically diverse Saturnian satellite Enceladus vigorously vents liquid water and vapor from fractures within a south polar depression and thus must have a liquid reservoir or active melting. However, the extent and location of any subsurface liquid region is not directly observable. We use measurements of control points across the surface of Enceladus accumulated over seven years of spacecraft observations to determine the satellite’s precise rotation state, finding a forced physical libration of 0.120 ± 0.014° (2σ). This value is too large to be consistent with Enceladus’s core being rigidly connected to its surface, and thus implies the presence of a global ocean rather than a localized polar sea. The maintenance of a global ocean within Enceladus is problematic according to many thermal models and so may constrain satellite properties or require a surprisingly dissipative Saturn.

First Detection of the Acoustic Oscillation Phase Shift Expected from the Cosmic Neutrino Background. Follin et al. 2015, PRL

PRL link

The unimpeded relativistic propagation of cosmological neutrinos prior to recombination of the baryon-photon plasma alters gravitational potentials and therefore the details of the time-dependent gravitational driving of acoustic oscillations. We report here a first detection of the resulting shifts in the temporal phase of the oscillations, which we infer from their signature in the cosmic microwave background temperature power spectrum.

ars technica

ANTARES neutrino detection and possible Swift X-ray counterpart

Indication of Gamma-Ray Emission from the Newly Discovered Dwarf Galaxy Reticulum II. Geringer-Sameth et al. 2015, PRL

PDF file

We present a search for γ-ray emission from the direction of the newly discovered dwarf galaxy Reticulum II. Using Fermi-LAT Collaboration data, we detect a signal that exceeds expected backgrounds between ∼2–10  GeV and is consistent with annihilation of dark matter for particle masses less than a few ×102  GeV. Modeling the background as a Poisson process based on Fermi-LAT diffuse models, and taking into account trial factors, we detect emission with p value less than 9.8×10−5 (>3.7σ). An alternative, model-independent treatment of the background reduces the significance, raising the p value to 9.7×10−3 (2.3σ). Even in this case, however, Reticulum II has the most significant γ-ray signal of any known dwarf galaxy. If Reticulum II has a dark-matter halo that is similar to those inferred for other nearby dwarfs, the signal is consistent with the s-wave relic abundance cross section for annihilation.

Probabilistic Programming in Python using PyMC

Angular momentum of disc galaxies with a lognormal density distribution
simple, fundamental scalings of disks

Central engine of a gamma-ray blazar resolved through the magnifying glass of gravitational microlensing (Neronov et al. 2015, Nature Physics)

Nature Physics paper

Gamma-ray emission from blazars is known to originate from jets emitted by supermassive black holes1. However, the exact location and size of the γ-ray emitting part of the jets is uncertain23456. The main difficulty is the very small angular size of these sources, beyond the angular resolution of γ-ray telescopes. Here, we report a measurement of the projected size of the γ-ray jet, revealed by the detection of microlensing in the gravitationally lensed blazar PKS 1830-211. This measurement is consistent with a constraint from the intrinsic variability timescale of the blazar. Our measurement shows that the γ-ray emission originates from the vicinity of the central supermassive black hole. Combining the X-ray and γ-ray data, we use the microlensing effect to constrain the size of the X-ray source. We show that the effect of pair production of γ-rays on X-ray photons does not make the source opaque, owing to the large size of the X-ray emission region.

(via Marco Ajello)

Discussion on "Promoting an open research culture"

Discussion based on the following note:

Promoting an open research culture, B. A. Nosek et al. Science 26 June 2015:
Vol. 348 no. 6242 pp. 1422-1425

"Transparency, openness, and reproducibility are readily recognized as vital features of science. When asked, most scientists embrace these features as disciplinary norms and values. Therefore, one might expect that these valued features would be routine in daily practice. Yet, a growing body of evidence suggests that this is not the case.'


We used the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) near-infrared camera to image the host galaxies of a sample of 11 luminous, dust-reddened quasars at $z\sim 2$—the peak epoch of black hole growth and star formation in the universe—to test the merger-driven picture for the coevolution of galaxies and their nuclear black holes. The red quasars come from the FIRST+2MASS red quasar survey and a newer, deeper, UKIDSS+FIRST sample. These dust-reddened quasars are the most intrinsically luminous quasars in the universe at all redshifts, and they may represent the dust-clearing transitional phase in the merger-driven black hole growth scenario. Probing the host galaxies in rest-frame visible light, the HST images reveal that 8/10 of these quasars have actively merging hosts, whereas one source is reddened by an intervening lower-redshift galaxy along the line of sight. We study the morphological properties of the quasar hosts using parametric Sérsic fits, as well as nonparametric estimators (Gini coefficient, M20, and asymmetry). Their properties are heterogeneous but broadly consistent with the most extreme morphologies of local merging systems such as ultraluminous infrared galaxies. The red quasars have a luminosity range of $\mathrm{log}({L}_{\mathrm{bol}})=47.8-48.3$ (erg s−1), and the merger fraction of their hosts is consistent with merger-driven models of luminous active galactic nuclei activity at z = 2, which supports the picture in which luminous quasars and galaxies coevolve through major mergers that trigger both star formation and black hole growth.

ApJ link

How gravity kills Schrödinger's cat

Theorists argue that warped space-time prevents quantum superpositions of large-scale objects.

Nature news

Nature physics paper


Supercritical accretion disks in ultraluminous X-ray sources and SS 433 (Fabrika et al. 2015, Nature Physics)

Nature Physics paper

The black hole mass and accretion rate in ultraluminous X-ray sources (ULXs) in external galaxies, whose X-ray luminosities exceed those of the brightest black holes in our Galaxy by hundreds and thousands of times12, is an unsolved problem. Here we report that all ULXs ever spectroscopically observed have almost the same optical spectra, apparently of WNL type (late nitrogen Wolf–Rayet stars) or LBV (luminous blue variables) in their hot state, which are very scarce stellar objects. We show that the spectra do not originate from WNL/LBV-type donors but from very hot winds from the accretion disks with nearly normal hydrogen content, which have similar physical conditions to the stellar winds from these stars. The optical spectra are similar to that of SS 433, the only known supercritical accretor in our Galaxy3, although the ULX spectra indicate a higher wind temperature. Our results suggest that ULXs with X-ray luminosities of ~1040 erg s−1 must constitute a homogeneous class of objects, which most likely have supercritical accretion disks.

ars technica link

Resonant interactions and chaotic rotation of Pluto’s small moons

Resonant interactions and chaotic rotation of Pluto’s small moons
M. R. Showalter and D. P. Hamilton
Nature 522, 45–49 (04 June 2015)

Editor's Summary: With NASA's New Horizons probe fast approaching Pluto for its flyby on 14 July, Mark Showalter and Douglas Hamilton present new results from the Pluto system and offer some predictions about what the spacecraft might observe. Pluto's four small moons — Styx, Nix, Kerberos and Hydra — follow near-circular, near-equatorial orbits around the central 'binary planet' comprising Pluto and its large moon, Charon. In an analysis of Hubble Space Telescope images, Showalter and Hamilton demonstrate that Styx, Nix and Hydra are tied together by a three-body resonance. Perturbations by the other bodies inject chaos into this otherwise stable configuration so that Nix and Hydra rotate chaotically, driven by the large torques of the Pluto–Charon binary. Nix and Hydra have bright surfaces similar to that of Charon. Kerberos may be much darker.


Link to paper

One aspect of the quantum nature of spacetime is its "foaminess" at very small scales. Many models for spacetime foam are defined by the accumulation power α, which parameterizes the rate at which Planck-scale spatial uncertainties (and the phase shifts they produce) may accumulate over large path lengths. Here α is defined by the expression for the path-length fluctuations, $\delta \ell $, of a source at distance , wherein $\delta \ell \simeq {{\ell }^{1-\alpha }}\ell _{{\rm P}}^{\alpha }$, with ${{\ell }_{{\rm P}}}$ being the Planck length. We reassess previous proposals to use astronomical observations of distant quasars and active galactic nuclei to test models of spacetime foam. We show explicitly how wavefront distortions on small scales cause the image intensity to decay to the point where distant objects become undetectable when the path-length fluctuations become comparable to the wavelength of the radiation. We use X-ray observations from Chandra to set the constraint $\alpha \gtrsim 0.58$, which rules out the random-walk model (with $\alpha =1/2$). Much firmer constraints can be set by utilizing detections of quasars at GeV energies with Fermi and at TeV energies with ground-based Cerenkov telescopes: $\alpha \gtrsim 0.67$ and $\alpha \gtrsim 0.72$, respectively. These limits on α seem to rule out $\alpha =2/3$, the model of some physical interest.


A strong ultraviolet pulse from a newborn type Ia supernova

Type Ia supernovae1 are destructive explosions of carbon-oxygen white dwarfs2, 3. Although they are used empirically to measure cosmological distances4, 5, 6, the nature of their progenitors remains mysterious3. One of the leading progenitor models, called the single degenerate channel, hypothesizes that a white dwarf accretes matter from a companion star and the resulting increase in its central pressure and temperature ignites thermonuclear explosion3, 7, 8. Here we report observations with the Swift Space Telescope of strong but declining ultraviolet emission from a type Ia supernova within four days of its explosion. This emission is consistent with theoretical expectations of collision between material ejected by the supernova and a companion star9, and therefore provides evidence that some type Ia supernovae arise from the single degenerate channel.

44Ti gamma-ray emission lines from SN1987A reveal an asymmetric explosion

In core-collapse supernovae, titanium-44 (44Ti) is produced in the innermost ejecta, in the layer of material directly on top of the newly formed compact object. As such, it provides a direct probe of the supernova engine. Observations of supernova 1987A (SN1987A) have resolved the 67.87- and 78.32–kilo–electron volt emission lines from decay of 44Ti produced in the supernova explosion. These lines are narrow and redshifted with a Doppler velocity of ~700 kilometers per second, direct evidence of large-scale asymmetry in the explosion.

Detection of water vapour around dwarf planet (1) Ceres

We report the detection of water vapour on (1) Ceres, the first unambiguous discovery of water on an object in the asteroid main belt. Most of the water vapour stems from localized regions at low latitude, possibly from surface features known from adaptive optics observations. We suggest either cometary-type sublimation from the near surface or cryovolcanism as the origin of the waver vapour [1].


Glory on Venus cloud tops and the unknown UV absorber


We report on the implications of the observations of the glory phenomenon made recently by Venus Express orbiter. Glory is an optical phenomenon that poses stringent constraints on the cloud properties. These observations thus enable us to constrain two properties of the particles at the cloud tops (about 70 km altitude) which are responsible for a large fraction of the solar energy absorbed by Venus. Firstly we obtain a very accurate estimate of the cloud particles size to be 1.2 μm with a very narrow size distribution. We also find that for the two observations presented here the clouds are homogenous, as far as cloud particles sizes are concerned, on scale of at least 1200 km. This is in contrast to previous estimates that were either local, from entry probes data, or averaged over space and time from polarization data. Secondly we find that the refractive index for the data discussed here is higher than that of sulfuric acid previously proposed for the clouds composition (Hansen, J.E., Hovenier, J.W. [1974]. J. Atmos. Sci. 31, 1137–1160; Ragent, B. et al. [1985]. Adv. Space Res. 5, 85–115). Assuming that the species contributing to the increase of the refractive index is the same as the unknown UV absorber, we are able to constrain the list of candidates. We investigated several possibilities and argue that either small ferric chloride (FeCl3) cores inside sulfuric acid particles or elemental sulfur coating their surface are good explanations of the observation. Both ferric chloride and elemental sulfur have been suggested in the past as candidates for the as yet unknown UV absorber (Krasnopolsky, V.A. [2006]. Planet. Space Sci. 54, 1352–1359; Mills, F.P. et al. [2007]. In: Esposito, L.W., Stofan, E.R., Cravens, T.E. (Eds.), Exploring Venus as a Terrestrial Planet, vol. 176. AGU Monogr. Ser., Washington, DC, pp. 73–100).

Isolated compact elliptical galaxies: Stellar systems that ran away

Igor Chilingarian, Ivan Zolotukhin

Abstract: Compact elliptical galaxies form a rare class of stellar system (~30 presently known) characterized by high stellar densities and small sizes and often harboring metal-rich stars. They were thought to form through tidal stripping of massive progenitors, until two isolated objects were discovered where massive galaxies performing the stripping could not be identified. By mining astronomical survey data, we have now found 195 compact elliptical galaxies in all types of environment. They all share similar dynamical and stellar population properties. Dynamical analysis for nonisolated galaxies demonstrates the feasibility of their ejection from host clusters and groups by three-body encounters, which is in agreement with numerical simulations. Hence, isolated compact elliptical and isolated quiescent dwarf galaxies are tidally stripped systems that ran away from their hosts.

Planet heating prevents inward migration of planetary cores

Pablo Benı´tez-Llambay1, Fre´de´ric Masset2, Gloria Koenigsberger2 & Judit Szula´gyi3

Planetary systems are born in the disks of gas, dust and rocky fragments that surround newly formed stars. Solid content assembles into ever-larger rocky fragments that eventually become planetary embryos. These then continue their growth by accreting leftover material in the disk. Concurrently, tidal effects in the disk cause a radial drift in the embryo orbits, a process known as migration1–4. Fast inward migration is predicted by theory for embryos smaller than three to fiveEarthmasses5–7. With only inwardmigration, these embryos can only rarely become giant planets located at Earth’s distance fromthe Sunand beyond8,9, incontrastwith observations10. Here we report that asymmetries in the temperature rise associated with accreting infalling material11,12 produce a force (which gives rise to an effect thatwe call ‘heating torque’) that counteracts inward migration.This provides a channel for the formation of giant planets 8 and also explains the strong planet–metallicity correlation found between the incidence of giant planets and the heavy-element abundance  of the host stars13,14.

Stochastic electron acceleration during spontaneous turbulent reconnection in a strong shock wave

  1. Y. Matsumoto1,*T. Amano2T. N. Kato3M. Hoshino2

Explosive phenomena such as supernova remnant shocks and solar flares have demonstrated evidence for the production of relativistic particles. Interest has therefore been renewed in collisionless shock waves and magnetic reconnection as a means to achieve such energies. Although ions can be energized during such phenomena, the relativistic energy of the electrons remains a puzzle for theory. We present supercomputer simulations showing that efficient electron energization can occur during turbulent magnetic reconnection arising from a strong collisionless shock. Upstream electrons undergo first-order Fermi acceleration by colliding with reconnection jets and magnetic islands, giving rise to a nonthermal relativistic population downstream. These results shed new light on magnetic reconnection as an agent of energy dissipation and particle acceleration in strong shock waves.

Saturn’s fast spin determined from its gravitational field and oblateness

The alignment of Saturn’s magnetic pole with its rotation axis precludes the use of magnetic field measurements to determine its rotation period1. The period was previously determined from radio measurements by the Voyager spacecraft to be 10 h 39 min 22.4 s (ref. 2). When the Cassini spacecraft measured a period of 10 h 47 min 6 s, which was additionally found to change between sequential measurements345, it became clear that the radio period could not be used to determine the bulk planetary rotation period. Estimates based upon Saturn’s measured wind fields have increased the uncertainty even more, giving numbers smaller than the Voyager rotation period, and at present Saturn’s rotation period is thought to be between 10 h 32 min and 10 h 47 min, which is unsatisfactory for such a fundamental property. Here we report a period of 10 h 32 min 45 s ± 46 s, based upon an optimization approach using Saturn’s measured gravitational field and limits on the observed shape and possible internal density profiles. Moreover, even when solely using the constraints from its gravitational field, the rotation period can be inferred with a precision of several minutes. To validate our method, we applied the same procedure to Jupiter and correctly recovered its well-known rotation period.

Eyelashes divert airflow to protect the eye

[quant-ph] Entanglement Enabled Intensity Interferometry

Intensity interferometry (Hanbury Brown - Twiss effect) is an interesting and useful concept that is usually presented as a manifestation of the quantum statistics of indistinguishable particles. Here, by exploiting possibilities for project and entanglement, we substantially widen the scope of its central idea, removing the requirement of indistinguishability. We thereby potentially gain access to a host of new observables, including subtle polarization correlations and entanglement itself. Our considerations also shed light on the physical significance of superselection.

Jupiter’s decisive role in the inner Solar System’s early evolution

Konstantin Batygin & Greg Laughlin

The statistics of extrasolar planetary systems indicate that the default mode of planet formation generates planets with orbital periods shorter than 100 days and masses substantially exceeding that of the Earth. When viewed in this context, the Solar System is unusual. Here, we present simulations which show that a popular formation scenario for Jupiter and Saturn, in which Jupiter migrates inward from a > 5 astronomical units (AU) to a ≈ 1.5 AU before reversing direction, can explain the low overall mass of the Solar System’s terrestrial planets, as well as the absence of planets with a < 0.4 AU. Jupiter’s inward migration entrained s ≳ 10−100 km planetesimals into low-order mean motion resonances, shepherding and exciting their orbits. The resulting collisional cascade generated a planetesimal disk that, evolving under gas drag, would have driven any preexisting short-period planets into the Sun. In this scenario, the Solar System’s terrestrial planets formed from gas-starved mass-depleted debris that remained after the primary period of dynamical evolution.

Dear Colleague: Status of NSF Response to NWNH Decadal Survey

Dear Colleague:
In August 2010, the National Research Council (NRC) released the most recent in its series of decadal surveys in Astronomy and Astrophysics, entitled “New Worlds, New Horizons in Astronomy and Astrophysics. [...] The budget for AST has remained stagnant, rather than increasing at the rate of 4 percent per year in purchasing power (plus inflation) assumed in NWNH. The Fiscal Year (FY) 2015 budget estimate for AST is USD 244.16 million, compared to an actual value of USD 246.53 million in FY 2010. Thus it has not been feasible to implement positive responses to all NWNH recommendations. [...] This letter is an update to the science community on the status of the AST response to NWNH.

Dear Colleague Letter: Status of NSF MPS/AST Response to Recommendations of New Worlds, New Horizons Decadal Survey

Membrane alternatives in worlds without oxygen: Creation of an azotosome

An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30

An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30
Xue-Bing Wu, Feige Wang, Xiaohui Fan, Weimin Yi, Wenwen Zuo, Fuyan Bian, Linhua Jiang, Ian D. McGreer, Ran Wang, Jinyi Yang, Qian Yang, David Thompson & Yuri Beletsky

Nature 518, 512–515 (26 February 2015)

Editor's summary:
Cosmic redshifts of between 6 and 7 represent a time when the intergalactic medium was in transition from a neutral state to being completely ionized. Here Xue-Bing Wu et al. report the discovery of an ultraluminous quasar at redshift z = 6.30 that has optical and near-infrared luminosity several times greater than previously known quasars at redshifts beyond 6. Based on near-infrared spectral data, the authors estimate a mass of approximately twelve-billion solar-masses for the associated black hole, consistent with the thirteen-billion solar masses derived by assuming an Eddington-limited accretion rate, where the force of radiation acting outwards and the gravitational force acting inwards are in balance. As the most luminous quasar known to date at z = 6, this object will be a useful resource for the study of galaxy formation around massive black holes at the end of the epoch of cosmic reionization.

A higher-than-predicted measurement of iron opacity at solar interior temperatures

Nearly a century ago it was recognized1 that radiation absorption by stellar matter controls the internal temperature profiles within stars. Laboratory opacity measurements, however, have never been performed at stellar interior conditions, introducing uncertainties in stellar models2345. A particular problem arose23678 when refined photosphere spectral analysis910 led to reductions of 30–50 per cent in the inferred amounts of carbon, nitrogen and oxygen in the Sun. Standard solar models11 using the revised element abundances disagree with helioseismic observations that determine the internal solar structure using acoustic oscillations. This could be resolved if the true mean opacity for the solar interior matter were roughly 15 per cent higher than predicted23678, because increased opacity compensates for the decreased element abundances. Iron accounts for a quarter of the total opacity212 at the solar radiation/convection zone boundary. Here we report measurements of wavelength-resolved iron opacity at electron temperatures of 1.9–2.3 million kelvin and electron densities of (0.7–4.0) × 1022 per cubic centimetre, conditions very similar to those in the solar region that affects the discrepancy the most: the radiation/convection zone boundary. The measured wavelength-dependent opacity is 30–400 per cent higher than predicted. This represents roughly half the change in the mean opacity needed to resolve the solar discrepancy, even though iron is only one of many elements that contribute to opacity.


2014 Update of the Discoveries of Nuclides

M. Thoennessen

The 2014 update of the discovery of nuclide project is presented. Only six new nuclides were observed for the first time in 2014 while the assignments of seventeen other nuclides were revised. In addition, for another fourteen nuclides the laboratories where they were discovered were reassigned.

Systematic inequality and hierarchy in faculty hiring networks

The faculty job market plays a fundamental role in shaping research priorities, educational outcomes, and career trajectories among scientists and institutions. However, a quantitative understanding of faculty hiring as a system is lacking. Using a simple technique to extract the institutional prestige ranking that best explains an observed faculty hiring network—who hires whose graduates as faculty—we present and analyze comprehensive placement data on nearly 19,000 regular faculty in three disparate disciplines. Across disciplines, we find that faculty hiring follows a common and steeply hierarchical structure that reflects profound social inequality. Furthermore, doctoral prestige alone better predicts ultimate placement than a U.S. News & World Report rank, women generally place worse than men, and increased institutional prestige leads to increased faculty production, better faculty placement, and a more influential position within the discipline. These results advance our ability to quantify the influence of prestige in academia and shed new light on the academic system.


The formation of a quadruple star system with wide separation

"The formation of a quadruple star system with wide separation", published in Nature, Feb 12th:

Detection of galaxy assembly bias

The double-degenerate, super-Chandrasekhar nucleus of the planetary nebula Henize 2–428


"The planetary nebula (PN) stage is the ultimate fate of stars with mass 1 to 8 solar masses (M⊙). The origin of their complex morphologies is poorly understood1 , although several mechanisms involving binary interaction have been proposed 2,3 . In close binary systems, the orbital separation is short enough for the primary star to overfill its Roche lobe as it expands during the Asymptotic Giant Branch (AGB) phase. The excess material ends up forming a common-envelope (CE) surrounding both stars. Drag forces would then result in the envelope being ejected into a bipolar PN whose equator is coincident with the orbital plane of the system. Systems in which both stars have ejected their envelopes and evolve towards the white dwarf (WD) stage are called double-degenerates. Here we report the case of Henize 2-428, the first double-degenerate binary which has, without any ambiguity, a total mass above the Chandrasekhar limit. According to its short orbital period (4.2 hours) and total mass (∼1.8 M⊙), the system should merge in 700 million years, triggering a Type Ia supernova (SN Ia) event. This finding supports the double-degenerate, super-Chandrasekhar evolutionary channel for the formation of SNe Ia4 ."

Planck 2015 Results

A Joint Analysis of BICEP2/Keck Array and Planck Data

We report the results of a joint analysis of data from BICEP2/Keck Array and Planck. BICEP2 and Keck Array have observed the same approximately 400 deg2 patch of sky centered on RA 0h, Dec. −57.5°. The combined maps reach a depth of 57 nK deg in Stokes Q and U in a band centered at 150 GHz. Planck has observed the full sky in polarization at seven frequencies from 30 to 353 GHz, but much less deeply in any given region (1.2 µK deg in Q and U at 143 GHz). We detect 150×353 cross-correlation in B-modes at high significance. We fit the single- and cross frequency power spectra at frequencies above 150 GHz to a lensed-ΛCDM model that includes dust and a possible contribution from inflationary gravitational waves (as parameterized by the tensor-to-scalar ratio r). We probe various model variations and extensions, including adding a synchrotron component in combination with lower frequency data, and find that these make little difference to the r constraint. Finally we present an alternative analysis which is similar to a map-based cleaning of the dust contribution, and show that this gives similar constraints. The final result is expressed as a likelihood curve for r, and yields an upper limit r0.05 < 0.12 at 95% confidence. Marginalizing over dust and r, lensing B-modes are detected at 7.0 σ significance.



Press releases:

BICEP2+Planck Press release

Bottom line:

No evidence for primordial gravitational waves:

(mars 2013)
(février 2014)
(décembre 2014)
(janvier 2015)
r < 0.11 r = 0.16-0.20 r < 0.11 r < 0.13

Wind-driven circulation in Titan's seas

A higher-than-predicted measurement of iron opacity at solar interior temperatures

"A higher-than-predicted measurement of iron opacity at solar interior temperatures" by Bailey et al.

Nearly a century ago it was recognized1 that radiation absorption by stellar matter controls the internal temperature profiles within stars. Laboratory opacity measurements, however, have never been performed at stellar interior conditions, introducing uncertainties in stellar models2, 3, 4, 5. A particular problem arose2, 3, 6, 7, 8 when refined photosphere spectral analysis9, 10 led to reductions of 30–50 per cent in the inferred amounts of carbon, nitrogen and oxygen in the Sun. Standard solar models11 using the revised element abundances disagree with helioseismic observations that determine the internal solar structure using acoustic oscillations. This could be resolved if the true mean opacity for the solar interior matter were roughly 15 per cent higher than predicted2, 3, 6, 7, 8, because increased opacity compensates for the decreased element abundances. Iron accounts for a quarter of the total opacity2, 12 at the solar radiation/convection zone boundary. Here we report measurements of wavelength-resolved iron opacity at electron temperatures of 1.9–2.3 million kelvin and electron densities of (0.7–4.0) × 1022 per cubic centimetre, conditions very similar to those in the solar region that affects the discrepancy the most: the radiation/convection zone boundary. The measured wavelength-dependent opacity is 30–400 per cent higher than predicted. This represents roughly half the change in the mean opacity needed to resolve the solar discrepancy, even though iron is only one of many elements that contribute to opacity.

Planck 2014 results

Planck Press Release Dec 1 2014 (in French, en francais)

Planck press release (now with polarization!) includes two more technical pages (both in French):

Dark Matter and (if I read the bottom panel correctly) no B-Modes and lensing B-modes

and Neutrinos (looks like N_eff ~ 3):

Solar nebula magnetic fields recorded in the Semarkona meteorite

PDF, Supplementary PDF


Magnetic fields are proposed to have played a critical role in some of the most enigmatic processes of planetary formation by mediating the rapid accretion of disk material onto the central star and the formation of the first solids. However, there have been no experimental constraints on the intensity of these fields. Here we show that dusty olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular field of 54 ± 21 μT. This intensity supports chondrule formation by nebular shocks or planetesimal collisions rather than by electric currents, the x-wind, or other mechanisms near the sun. This implies that background magnetic fields in the terrestrial planet-forming region were likely 5-54 μT, which is sufficient to account for measured rates of mass and angular momentum transport in protoplanetary disks.

Unusual Activity in the Atmosphere of Uranus in 2014

Announced at DPS. No paper posted yet. UCB Press release:



Uranus continues to evolve as it progresses through the post-equinoctial season. Images taken on 5 and 6 August 2014 at the 10-m Keck 2 telescope show significant atmospheric activity in the planet’s northern (currently sun-facing) hemisphere. Although Keck’s adaptive optics system was underperforming (resulting in artifacts and some blurring), many discrete features were visible on the planet at H (1.6 microns) and K’ (2.2 microns). Many of these features reached altitudes above the 1-bar level, as evidenced by their detection at K’. One feature breaks the record as the brightest ever detected or Uranus at K', producing 30% of the total light reflected by the planet in that filter, compared to 12% for the previous record in 2005 (Sromovsky et al., Icarus 192, 558-575, 2007). The 2014 feature’s morphology was similar at both K’ and H, suggestive of an underlying vortex (e.g., Hammel et al., Icarus 201, 257-271, 2009). However, the feature’s brightest region in K' is not particularly bright in H; i.e, although it is relatively high in altitude, it does not have a high optical depth. The total light fraction at H is only 2-3%, compared to the 4-5% found for the 2005 feature. Thus, its visible-wavelength contrast may be low; this could explain why there have been no amateur follow-up detections as of this writing. The new images also reveal development of a long-expected north polar haze as well as polar cloud features. Interestingly, some discrete polar features were visible through the polar haze. This may indicate that the northern polar haze is not yet at an optical depth comparable to that of the fully-formed southern polar haze seen in pre-equinoctial years. Acknowledgements: the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among Caltech, University of California and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation. The authors acknowledge the significant cultural role of Mauna Kea’s summit, and extend thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests.

Punga Mare Waves

Cassini/VIMS observes rough surfaces on Titan’s Punga Mare in specular reflection

The Science of the Movie "Interstellar"

There's been quite a bit of chatter on the internet regarding the validity of some of the science presented in the movie. It's not often that this little corner of astrophysics gets such a public presentation, so I figured it might be interesting for astrophysics institutions to discuss the movie for a few minutes around the water cooler.

Birth of Planets Revealed in Astonishing Detail in ALMA's 'Best Image Ever'

[NRAO Press Release]

Astronomers have captured the best image ever of planet formation around an infant star as part of the testing and verification process for the Atacama Large Millimeter/submillimeter Array’s (ALMA) new high-resolution capabilities.

This revolutionary new image reveals in astonishing detail the planet-forming disk surrounding HL Tau, a Sun-like star located approximately 450 light-years from Earth in the constellation Taurus.

ALMA uncovered never-before-seen features in this system, including multiple concentric rings separated by clearly defined gaps. These structures suggest that planet formation is already well underway around this remarkably young star... [abridged]


See also Phil Plait's blog post:

Pulsations as a driver for LBV variability

Pulsations as a driver for LBV variability
Lovekin, C. C. ; Guzik, J. A.
Monthly Notices of the Royal Astronomical Society, Volume 445, Issue 2, p.1766-1773
Published in Dec 2014

Among the most spectacular variable stars are the luminous blue variables (LBVs), which can show three types of variability. The LBV phase of evolution is poorly understood, and the driving mechanisms for the variability are not known. The most common type of variability, the S Dor instability, occurs on time-scales of tens of years. During an S Dor outburst, the visual magnitude of the star increases, while the bolometric magnitude stays approximately constant. In this work, we investigate pulsation as a possible trigger for the S Dor-type outbursts. We calculate the pulsations of envelope models using a non-linear hydrodynamic code including a time-dependent convection treatment. We initialize the pulsation in the hydrodynamic model based on linear non-adiabatic calculations. Pulsation properties for a full grid of models from 20 to 85 M were calculated, and in this paper, we focus on the few models that show either long-period pulsations or outburst-like behaviour, with photospheric radial velocities reaching 70-80 km s-1. At the present time, our models cannot follow mass-loss, so once the outburst event begins, our simulations are terminated. Our results show that pulsations alone are not able to drive enough surface expansion to eject the outer layers. However, the outbursts and long-period pulsations discussed here produce large variations in effective temperature and luminosity, which are expected to produce large variations in the radiatively driven mass-loss rates.

An ultraluminous X-ray source powered by an accreting neutron star

The majority of ultraluminous X-ray sources are point sources that are spatially offset from the nuclei of nearby galaxies and whose X-ray luminosities exceed the theoretical maximum for spherical infall (the Eddington limit) onto stellar-mass black holes12. Their X-ray luminosities in the 0.5–10 kiloelectronvolt energy band range from 1039 to 1041 ergs per second3. Because higher masses imply less extreme ratios of the luminosity to the isotropic Eddington limit, theoretical models have focused on black hole rather than neutron star systems12. The most challenging sources to explain are those at the luminous end of the range (more than 1040 ergs per second), which require black hole masses of 50–100 times the solar value or significant departures from the standard thin disk accretion that powers bright Galactic X-ray binaries, or both. Here we report broadband X-ray observations of the nuclear region of the galaxy M82 that reveal pulsations with an average period of 1.37 seconds and a 2.5-day sinusoidal modulation. The pulsations result from the rotation of a magnetized neutron star, and the modulation arises from its binary orbit. The pulsed flux alone corresponds to an X-ray luminosity in the 3–30 kiloelectronvolt range of 4.9 × 1039 ergs per second. The pulsating source is spatially coincident with a variable source4 that can reach an X-ray luminosity in the 0.3–10 kiloelectronvolt range of 1.8 × 1040 ergs per second1. This association implies a luminosity of about 100 times the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects.

Data Smashing

Data Smashing

Ishanu Chattopadhyay, Hod Lipson
ArXiv: 1401.0742

Investigation of the underlying physics or biology from empirical data requires a quantifiable notion of similarity - when do two observed data sets indicate nearly identical generating processes, and when they do not. The discriminating characteristics to look for in data is often determined by heuristics designed by experts, e.g., distinct shapes of "folded" lightcurves may be used as "features" to classify variable stars, while determination of pathological brain states might require a Fourier analysis of brainwave activity. Finding good features is non-trivial. Here, we propose a universal solution to this problem: [...] In our examples, the data smashing principle, without access to any domain knowledge, meets or exceeds the performance of specialized algorithms tuned by domain experts.

Water vapor absorption in the clear atmosphere of a Neptune-sized exoplanet

J. Fraine, D. Deming, B. Benneke, H. Knutson, A. Jordan, N. Espinoza, N. Madhusudhan, A. Wilkins & K. Todorov

Transmission spectroscopy has so far detected atomic and molecular absorption in Jupiter-sized exoplanets, but intense efforts to measure molecular absorption in the atmospheres of smaller (Neptune-sized) planets during transits have revealed only featureless spectra1, 2, 3, 4. From this it was concluded that the majority of small, warm planets evolve to sustain atmospheres with high mean molecular weights (little hydrogen), opaque clouds or scattering hazes, reducing our ability to observe the composition of these atmospheres1, 2, 3, 4, 5. Here we report observations of the transmission spectrum of the exoplanet HAT-P-11b (which has a radius about four times that of Earth) from the optical wavelength range to the infrared. We detected water vapour absorption at a wavelength of 1.4 micrometres. The amplitude of the water absorption (approximately 250 parts per million) indicates that the planetary atmosphere is predominantly clear down to an altitude corresponding to about 1 millibar, and sufficiently rich in hydrogen to have a large scale height (over which the atmospheric pressure varies by a factor of e). The spectrum is indicative of a planetary atmosphere in which the abundance of heavy elements is no greater than about 700 times the solar value. This is in good agreement with the core-accretion theory of planet formation, in which a gas giant planet acquires its atmosphere by accreting hydrogen-rich gas directly from the protoplanetary nebula onto a large rocky or icy core6.

Use “Dead Weight” on Mars Spacecraft to Advance Science and Technology

NASA is looking for creative yet practical ideas to find a dual purpose for Balance mass (“dead weight”) that is jettisoned from Mars landers like the Mars Science Laboratory (MSL) to balance the spacecraft during entry and landing. Payloads replacing Balance mass should perform some type of scientific or technological function adding to our knowledge base while closely matching the volume and weight characteristics of the original Balance mass. Ideas are welcomed from all disciplines. This Challenge requires only a written proposal.

Cash awards up to $1 million.

AMS-02 Press Release on CR Electrons and Positrons

CERN press release including updated positron fraction results

High Statistics Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5–500 GeV with the Alpha Magnetic Spectrometer on the International Space Station

Phys. Rev. Lett. 113, 121101 – Published 18 September 2014
L. Accardo et al. (AMS Collaboration)

Electron and Positron Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

Phys. Rev. Lett. 113, 121102 – Published 18 September 2014
M. Aguilar et al. (AMS Collaboration)

Neutrinos from the primary proton–proton fusion process in the Sun

Borexino Collaboration

In the core of the Sun, energy is released through sequences of nuclear reactions that convert hydrogen into helium. The primary reaction is thought to be the fusion of two protons with the emission of a low-energy neutrino. These so-called pp neutrinos constitute nearly the entirety of the solar neutrino flux, vastly outnumbering those emitted in the reactions that follow. Although solar neutrinos from secondary processes have been observed, proving the nuclear origin of the Sun’s energy and contributing to the discovery of neutrino oscillations, those from proton–proton fusion have hitherto eluded direct detection. Here we report spectral observations of pp neutrinos, demonstrating that about 99 per cent of the power of the Sun, 3.84 × 1033 ergs per second, is generated by the proton–proton fusion process.

Online networks and subjective well-being

A chemical signature of first-generation very massive stars

by W. Aoki, N. Tominaga, T. C. Beers, S. Honda, Y. S. Lee

Numerical simulations of structure formation in the early universe predict the formation of some fraction of stars with several hundred solar masses. No clear evidence of supernovae from such very massive stars has, however, yet been found in the chemical compositions of Milky Way stars. We report on an analysis of a very metal-poor star SDSS J001820.5–093939.2, which possesses elemental-abundance ratios that differ significantly from any previously known star. This star exhibits low [α-element Fe] ratios and large contrasts between the abundances of odd and even element pairs, such as scandium/titanium and cobalt/nickel. Such features have been predicted by nucleosynthesis models for supernovae of stars more than 140 times as massive as the Sun, suggesting that the mass distribution of first-generation stars might extend to 100 solar masses or larger.

A 400-solar-mass black hole in the galaxy M82

by Dheeraj R. Pasham, Tod E. Strohmayer & Richard F. Mushotzky

M82 X-1, the brightest X-ray source in the galaxy M82, has been thought to be an intermediate-mass black hole (100 to 10,000 solar masses) because of its extremely high luminosity and variability characteristics1, 2, 3, 4, 5, 6, although some models suggest that its mass may be only about 20 solar masses3, 7. The previous mass estimates were based on scaling relations that use low-frequency characteristic timescales which have large intrinsic uncertainties8, 9. For stellar-mass black holes, we know that the high-frequency quasi-periodic oscillations (100–450 hertz) in the X-ray emission that occur in a 3:2 frequency ratio are stable and scale in frequency inversely with black hole mass with a reasonably small dispersion10, 11, 12, 13, 14, 15. The discovery of such stable oscillations thus potentially offers an alternative and less ambiguous means of mass determination for intermediate-mass black holes, but has hitherto not been realized. Here we report stable, twin-peak (3:2 frequency ratio) X-ray quasi-periodic oscillations from M82 X-1 at frequencies of 3.32 ± 0.06 hertz and 5.07 ± 0.06 hertz. Assuming that we can extrapolate the inverse-mass scaling that holds for stellar-mass black holes, we estimate the black hole mass of M82 X-1 to be 428 ± 105 solar masses. In addition, we can estimate the mass using the relativistic precession model, from which we get a value of 415 ± 63 solar masses.

Spectral Calibration in the Mid-Infrared: Challenges and Solutions

Spectral Calibration in the Mid-Infrared: Challenges and Solutions

G.C. Sloan (Cornell), T.L. Herter (Cornell), V. Charmandaris (Univ. of Crete), K. Sheth (NRAO), M. Burgdorf (HE Space Operations, Bremen), and J.R. Houck (Cornell)

2014, AJ, in press.

Full manuscript available locally (PDF).

The 53 IRS spectra described in this paper are available on this website.

We present spectra obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope of 33 K giants and 20 A dwarfs to assess their suitability as spectrophotometric standard stars. The K giants confirm previous findings that the strength of the SiO absorption band at 8 um increases for both later optical spectral classes and redder (B-V)0 colors, but with considerable scatter. For K giants, the synthetic spectra underpredict the strengths of the molecular bands from SiO and OH. For these reasons, the assumed true spectra for K giants should be based on neither the assumption that molecular band strengths in the infrared can be predicted accurately from optical spectral class or color nor synthetric spectra. The OH bands in K giants grow stronger with cooler stellar temperatures, and they are stronger than predicted by synthetic spectra. As a group, A dwarfs are better behaved and more predictable than the K giants, but they are more likely to show red excesses from debris disks. No suitable A dwarfs were located in parts of the sky continuously observable from Spitzer, and with previous means of estimating the true spectra of K giants ruled out, it was necessary to use models of A dwarfs to calibrate spectra of K giants from observed spectral ratios of the two groups and then use the calibrated K giants as standards for the full database of infrared spectra from Spitzer. We also describe a lingering artifact that affects the spectra of faint blue sources at 24 µm.


Velocity anti-correlation of diametrically opposed galaxy satellites in the low-redshift Universe

Neil G. Ibata, Rodrigo A. Ibata, Benoit Famaey & Geraint F. Lewis

Recent work has shown that the Milky Way and the Andromeda galaxies both possess the unexpected property that their dwarf satellite galaxies are aligned in thin and kinematically coherent planar structures. It is interesting to evaluate the incidence of such planar structures in the larger galactic population, because the Local Group may not be a representative environment. Here we report measurements of the velocities of pairs of diametrically opposed satellite galaxies. In the local Universe (redshift z < 0.05), we find that satellite pairs out to a distance of 150 kiloparsecs from the galactic centre are preferentially anti-correlated in their velocities (99.994 per cent confidence level), and that the distribution of galaxies in the larger-scale environment (out to distances of about 2 megaparsecs) is strongly clumped along the axis joining the inner satellite pair (>7σ confidence). This may indicate that planes of co-rotating satellites, similar to those seen around the Andromeda galaxy, are ubiquitous, and their coherent motion suggests that they represent a substantial repository of angular momentum on scales of about 100 kiloparsecs.

Published BICEP2 Results

Slightly revised from

Just one proposal per year, please, NSF tells astronomers

Later this summer, NSF's astronomy division intends to announce a new policy that will “strongly encourage” scientists to submit just a single proposal for each annual funding cycle. The voluntary cap is designed to boost success rates, which would please applicants. It's also meant to ease the workload and frustration levels of peer reviewers poring over proposals that they know have little chance of getting funded.

“It's a first step,” says James Ulvestad, director of NSF's astronomy division. If it doesn't achieve the desired effect, he adds, “we may have to make it mandatory in 2016 for the sake of reviewers' sanity.”

Science 20 June 2014:
Vol. 344 no. 6190 p. 1328
DOI: 10.1126/science.344.6190.1328

A Wolf-Rayet-like progenitor of SN 2013cu from spectral observations of a stellar wind

Gal-Yam et al. 2014

The explosive fate of massive Wolf-Rayet stars (WRSs) is a key open question in stellar physics. An appealing option is that hydrogen-deficient WRSs are the progenitors of some hydrogen-poor supernova explosions of types IIb, Ib and Ic (ref. 2). A blue object, having luminosity and colours consistent with those of some WRSs, has recently been identified in pre-explosion images at the location of a supernova of type Ib (ref. 3), but has not yet been conclusively determined to have been the progenitor. Similar work has so far only resulted in non-detections. Comparison of early photometric observations of type Ic supernovae with theoretical models suggests that the progenitor stars had radii of less than 1012 centimetres, as expected for some WRSs. The signature of WRSs, their emission line spectra, cannot be probed by such studies. Here we report the detection of strong emission lines in a spectrum of type IIb supernova 2013cu (iPTF13ast) obtained approximately 15.5 hours after explosion (by `flash spectroscopy', which captures the effects of the supernova explosion shock breakout flash on material surrounding the progenitor star). We identify Wolf-Rayet-like wind signatures, suggesting a progenitor of the WN(h) subclass (those WRSs with winds dominated by helium and nitrogen, with traces of hydrogen). The extent of this dense wind may indicate increased mass loss from the progenitor shortly before its explosion, consistent with recent theoretical predictions.

The Open Journal of Astrophysics

Discussion of

The different neighbours around Type-1 and Type-2 active galactic nuclei

Beatriz Villaroel and Andreas J. Korn, 2014, Nature Physics, "The different neighbours around Type-1 and Type-2 active galactic nuclei"

News and Views
Martin Gaskell, "Astronomy: Unifying active galactic nuclei"


Abstract: One of the most intriguing open issues in galaxy evolution is the structure and evolution of active galactic nuclei (AGN) that emit intense light believed to come from an accretion disk near a super massive black hole12. To understand the zoo of different AGN classes, it has been suggested that all AGN are the same type of object viewed from different angles3. This model—called AGN unification—has been successful in predicting, for example, the existence of hidden broad optical lines in the spectrum of many narrow-line AGN. But this model is not unchallenged4 and it is debatable whether more than viewing angle separates the so-called Type-1 and Type-2 AGN. Here we report the first large-scale study that finds strong differences in the galaxy neighbours to Type-1 and Type-2 AGN with data from the Sloan Digital Sky Survey (SDSS; ref. 5) Data Release 7 (DR7; ref. 6) and Galaxy Zoo78. We find strong differences in the colour and AGN activity of the neighbours to Type-1 and Type-2 AGN and in how the fraction of AGN residing in spiral hosts changes depending on the presence or not of a neighbour. These findings suggest that an evolutionary link between the two major AGN types might exist.


Properties of galaxies reproduced by a hydrodynamic simulation

by M. Vogelsberger, S. Genel, V. Springel, P. Torrey, D. Sijacki, D. Xu, G. Snyder, S. Bird, D. Nelson & L. Hernquist

Previous simulations of the growth of cosmic structures have broadly reproduced the ‘cosmic web’ of galaxies that we see in the Universe, but failed to create a mixed population of elliptical and spiral galaxies, because of numerical in- accuracies and incomplete physical models. Moreover, they were unable to track the small-scale evolution of gas and stars to the present epoch within a representative portion of the Universe. Here we report a simulation that starts 12 million years after the Big Bang, and traces 13 billion years of cosmic evolution with 12 billion resolution elements in a cube of 106.5 megaparsecs a side. It yields a reasonable population of ellipticals and spirals, reproduces the observed distribution of galaxies in clusters and characteristics of hydrogen on large scales, and at the same time matches the ‘metal’ and hydrogen content of galaxies on small scales.


Tegmark Inflation Chapter

Guest post by Max Tegmark on Sean Carroll's blog Preposterous Universe about inflation.

Discovery of a ~250 K Brown Dwarf at 2 pc from the Sun

Abstract: Through a previous analysis of multi-epoch astrometry from the Wide-field Infrared Survey Explorer (WISE), I identified WISE J085510.83–071442.5 as a new high proper motion object. By combining astrometry from WISE and the Spitzer Space Telescope, I have measured a proper motion of 8.1 ± 0.1'' yr–1 and a parallax of 0.454 ± 0.045'' ($2.20^{+0.24}_{-0.20}$ pc) for WISE J085510.83–071442.5, giving it the third highest proper motion and the fourth largest parallax of any known star or brown dwarf. It is also the coldest known brown dwarf based on its absolute magnitude at 4.5 μm and its color in [3.6]-[4.5]. By comparing M 4.5 with the values predicted by theoretical evolutionary models, I estimate an effective temperature of 225-260 K and a mass of 3-10 M Jup for the age range of 1-10 Gyr that encompasses most nearby stars.


An Earth-Sized Planet in the Habitable Zone of a Cool Star

Quintana et al., Science, 18 April 2014

The quest for Earth-like planets is a major focus of current exoplanet research. Although planets that are Earth-sized and smaller have been detected, these planets reside in orbits that are too close to their host star to allow liquid water on their surfaces. We present the detection of Kepler-186f, a 1.11 ± 0.14 Earth-radius planet that is the outermost of five planets, all roughly Earth-sized, that transit a 0.47 ± 0.05 solar-radius star. The intensity and spectrum of the star’s radiation place Kepler-186f in the stellar habitable zone, implying that if Kepler-186f has an Earth-like atmosphere and water at its surface, then some of this water is likely to be in liquid form.

The bathymetry of a Titan sea

A Necro-Biological Explanation for the Fermi Paradox

Liquid water on Enceladus

The Gravity Field and Interior Structure of Enceladus

L. Iess, D. J. Stevenson, M. Parisi, D. Hemingway, R. A. Jacobson, J. I. Lunine, F. Nimmo, J. W. Armstrong, S. W. Asmar, M. Ducci, P. Tortora

Science, 4 April 2014
Vol. 344 no. 6179 pp. 78-80
DOI: 10.1126/science.1250551

Editor's Summary: Saturn's moon Enceladus has often been the focus of flybys of the Cassini spacecraft. Although small—Enceladus is roughly 10 times smaller than Saturn's largest moon, Titan—Enceladus has shown hints of having a complex internal structure rich in liquid water. Iess et al. used long-range data collected by the Cassini spacecraft to construct a gravity model of Enceladus. The resulting gravity field indicates the presence of a large mass anomaly at its south pole. Calculations of the moment of inertia and hydrostatic equilibrium from the gravity data suggest the presence of a large, regional subsurface ocean 30 to 40 km deep.

Testing the Limits of Accretion

Felix proposes to discuss these papers at our next meeting (click the links to download the PDF [access to Science Mag. required]):

Soria et al.:


A Sedna-like body with a perihelion of 80 astronomical units

The observable Solar System can be divided into three distinct regions: the rocky terrestrial planets including the asteroids at 0.39 to 4.2 astronomical units (AU) from the Sun (where 1 AU is the mean distance between Earth and the Sun), the gas giant planets at 5 to 30 AU from the Sun, and the icy Kuiper belt objects at 30 to 50 AU from the Sun. The 1,000-kilometre-diameter dwarf planet Sedna was discovered ten years ago and was unique in that its closest approach to the Sun (perihelion) is 76 AU, far greater than that of any other Solar System body1. Formation models indicate that Sedna could be a link between the Kuiper belt objects and the hypothesized outer Oort cloud at around 10,000 au from the Sun2, 3, 4, 5, 6. Here we report the presence of a second Sedna-like object, 2012 VP113, whose perihelion is 80 au. The detection of 2012 VP113 confirms that Sedna is not an isolated object; instead, both bodies may be members of the inner Oort cloud, whose objects could outnumber all other dynamically stable populations in the Solar System.

A ring system detected around the Centaur (10199) Chariklo

Hitherto, rings have been found exclusively around the four giant planets in the Solar System. Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report observations of a multichord stellar occultation that revealed the presence of a ring system around (10199) Chariklo, which is a Centaur—that is, one of a class of small objects orbiting primarily between Jupiter and Neptune—with an equivalent radius of 124 $\pm$ 9 kilometres. There are two dense rings, with respective widths of about 7 and 3 kilometres, optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometres. The present orientation of the ring is consistent with an edge-on geometry in 2008, which provides a simple explanation for the dimming of the Chariklo system between 1997 and 2008, and for the gradual disappearance of ice and other absorption features in its spectrum over the same period. This implies that the rings are partly composed of water ice. They may be the remnants of a debris disk, possibly confined by embedded, kilometre-sized satellites.

Putative Indigenous Carbon-Bearing Alteration Features in Martian Meteorite Yamato 000593

We report the first observation of indigenous carbonaceous matter in the martian meteorite Yamato 000593. The carbonaceous phases are heterogeneously distributed within secondary iddingsite alteration veins and present in a range of morphologies including areas composed of carbon-rich spheroidal assemblages encased in multiple layers of iddingsite. We also observed microtubular features emanating from iddingsite veins penetrating into the host olivine comparable in shape to those interpreted to have formed by bioerosion in terrestrial basalts.

Key Words: Meteorite—Yamato 000593—Mars—Carbon.

Astrobiology 14, 170–181.

Hydrous mantle transition zone indicated by ringwoodite included within diamond

The ultimate origin of water in the Earth’s hydrosphere is in the deep Earth—the mantle. Theory and experiments have shown that although the water storage capacity of olivine-dominated shallow mantle is limited, the Earth’s transition zone, at depths between 410 and 660 kilometres, could be a major repository for water, owing to the ability of the higher-pressure polymorphs of olivine—wadsleyite and ringwoodite—to host enough water to comprise up to around 2.5 per cent of their weight. A hydrous transition zone may have a key role in terrestrial magmatism and plate tectonics, yet despite experimental demonstration of the water-bearing capacity of these phases, geophysical probes such as electrical conductivity have provided conflicting results, and the issue of whether the transition zone contains abundant water remains highly controversial. Here we report X-ray diffraction, Raman and infrared spectroscopic data that provide, to our knowledge, the first evidence for the terrestrial occurrence of any higher-pressure polymorph of olivine: we find ringwoodite included in a diamond from Juína, Brazil. The water-rich nature of this inclusion, indicated by infrared absorption, along with the preservation of the ringwoodite, is direct evidence that, at least locally, the transition zone is hydrous, to about 1 weight per cent. The finding also indicates that some kimberlites must have their primary sources in this deep mantle region.

Apologies for the nature paywall.

Super-Eddington Mechanical Power of an Accreting Black Hole in M83


Mass accretion onto black holes releases energy in the form of radiation and outflows. While the radiative flux cannot substantially exceed the Eddington limit, at which the outgoing radiation pressure impedes the inflow of matter, it remains unclear whether the kinetic energy flux is bounded by this same limit. Here we present the detection of a radio/optical structure, powered by outflows from a non-nuclear black hole. Its accretion disk properties indicate that this black hole is less than 100 solar masses. The optical/IR line emission implies an average kinetic power of 3 × 1040 erg s−1, higher than the Eddington luminosity of the black hole. These results demonstrate kinetic power exceeding the Eddington limit over a sustained period, which implies greater ability to influence the evolution of the black hole’s environment.

The observable signature of late heating of the Universe during cosmic reionization

Felix will lead a discussion on the recent Nature paper (click here to get the article), which is about role of HMXBs in the reionisation of the universe.

Astrotrends: interactively explore keyword trends in the literature

This interactive visualization shows the number of refereed Astronomy articles published each year, containing the selected keywords in their abstracts.

Firewall controversy claims black hole event horizons as latest victim

Information Preservation and Weather Forecasting for Black Holes

(Submitted on 22 Jan 2014)

It has been suggested [1] that the resolution of the information paradox for evaporating black holes is that the holes are surrounded by firewalls, bolts of outgoing radiation that would destroy any infalling observer. Such firewalls would break the CPT invariance of quantum gravity and seem to be ruled out on other grounds. A different resolution of the paradox is proposed, namely that gravitational collapse produces apparent horizons but no event horizons behind which information is lost. This proposal is supported by ADS-CFT and is the only resolution of the paradox compatible with CPT. The collapse to form a black hole will in general be chaotic and the dual CFT on the boundary of ADS will be turbulent. Thus, like weather forecasting on Earth, information will effectively be lost, although there would be no loss of unitarity.

Supernova in M82

Steve Fossey's page re discovery of SN in M82

Observation of the Optical and Spectral Characteristics of Ball Lightning

Ball lightning (BL) has been observed with two slitless spectrographs at a distance of 0.9 km. The BL is generated by a cloud-to-ground lightning strike. It moves horizontally during the luminous duration. The evolution of size, color, and light intensity is reported in detail. The spectral analysis indicates that the radiation from soil elements is present for the entire lifetime of the BL

See also:


Citizen scientists discover gravitational lenses at record speed


This week, encouraged by a program on the BBC, more than 55,000 citizen scientists powered up their computers, navigated to and, over the course of just 72 hours, made a difference to the future of astrophysics. [T]he first of the three daily episodes of the BBC television series Stargazing Live, which highlights astronomy research in the United Kingdom, included a challenge encouraging viewers to find [gravitational lenses] at the edge of space through The response was immense. Tens of thousands of people visited the website and, in just three days, made more than 6 million image classifications. The images that viewers classified were from infrared data taken with the CFHT telescope in Hawaii and the VISTA telescope in Chile by the VICS82 survey team, led by Jim Geach of the University of Hertfordshire. The patch of sky in question, though previously imaged with optical telescopes, had never before been searched for gravitational lenses in the infrared.

A preliminary analysis of citizen scientists’ work over the past week revealed a handful of new gravitational lenses, including one confirmed system that was found quickly enough that, during the second night’s TV program, researchers were able to point the UK's eMerlin radio array at the system to study it further. In addition to kick-starting research into these dusty and distant galaxies, Marshall says that the overwhelming amount of interest shown by citizen scientists in the past week may also have implications for future data-intensive experiments like the Large Synoptic Survey Telescope.


Summary extracted and condensed from the original article.

ITA/ITP Heidelberg Journal Club

The first 2014 meeting will be held on Tuesday, January 14th at 13:00 in the room 105 of Philosophenweg 12.

We will have two speakers and a discussion session.

Hope to see you there!

Effect of increased gravitational acceleration in potato deep-fat frying

This work extends our previous studies on crust thickness evolution and evaporation front propagation during deep fat frying of potato sticks (French fries) by incorporating the effect of increased gravitational acceleration. Scaling of gravitational acceleration allows scaling of buoyancy forces which control the heat transfer from hot oil to potato surface. For this, a special device is constructed which permits (a) temperature recording at specified positions below the potato surface (i.e. 0.5, 1.0 and 1.5 mm), (b) exposure of only one surface of a potato stick to hot oil, (c) rotation of the exposed surface at orientations 0° (horizontal, top), 90° (vertical, side) and 180° (horizontal, bottom), and (d) execution of deep fat frying experiments at increased gravity levels (i.e. 1.8, 3.0, 6.0 and 9.0 · gearth). The latter is achieved by means of a large diameter centrifuge (European Space Agency). Temperature recordings and crust thickness evolution indicate that heat transfer during frying depends on gravity level but differently at different potato orientations. Most significant variations with gravity are found up to 3.0 · gearth and for 0° orientation. Moreover, crust thickness evolution diverges from the evaporation front propagation in all times supporting the notion of a wide evaporation zone rather than a sharp evaporation front.

Searching the Internet for evidence of time travelers

Authors: Robert J. Nemiroff, Teresa Wilson
(Submitted on 26 Dec 2013)

Time travel has captured the public imagination for much of the past century, but little has been done to actually search for time travelers. Here, three implementations of Internet searches for time travelers are described, all seeking a prescient mention of information not previously available. The first search covered prescient content placed on the Internet, highlighted by a comprehensive search for specific terms in tweets on Twitter. The second search examined prescient inquiries submitted to a search engine, highlighted by a comprehensive search for specific search terms submitted to a popular astronomy web site. The third search involved a request for a direct Internet communication, either by email or tweet, pre-dating to the time of the inquiry. Given practical verifiability concerns, only time travelers from the future were investigated. No time travelers were discovered. Although these negative results do not disprove time travel, given the great reach of the Internet, this search is perhaps the most comprehensive to date.

Viewpoint: What’s Inside a Black Hole’s Horizon?

The martian soil as a planetary gas pump

Mars has an active surface, with omnipresent small dust particles and larger debris. With an ambient pressure below 10 mbar, which is less than 1% of the surface pressure on Earth, its CO2 atmosphere is rather tenuous. Aeolian processes on the surface such as drifting dunes, dust storms and dust devils are nevertheless still active1, 2, 3. The transport of volatiles below the surface, that is, through the porous soil, is unseen but needs to be known for balancing mass flows4, 5. Here, we describe a mechanism of forced convection within porous soils. At an average ambient gas pressure of 6 mbar, gas flow through the porous ground of Mars by thermal creep is possible and the soil acts as a (Knudsen) pump. Temperature gradients provided by local and temporal variations in solar insolation lead to systematic gas flows. Our measurements show that the flow rates can outnumber diffusion rates. Mars is the only body in the Solar System on which this can occur naturally. Our laboratory experiments reveal that the surface of Mars is efficient in cycling gas through layers at least centimetres above and below the soil with a turnover time of only seconds to minutes.

Puzzling accretion onto a black hole in the ultraluminous X-ray source M 101 ULX-1

There are two proposed explanations for ultraluminous X-ray sources1, 2 (ULXs) with luminosities in excess of 1039 erg s−1. They could be intermediate-mass black holes (more than 100–1,000 solar masses, ) radiating at sub-maximal (sub-Eddington) rates, as in Galactic black-hole X-ray binaries but with larger, cooler accretion disks3, 4, 5. Alternatively, they could be stellar-mass black holes radiating at Eddington or super-Eddington rates2, 6. On its discovery, M 101 ULX-14, 7 had a luminosity of 3 × 1039 erg s−1 and a supersoft thermal disk spectrum with an exceptionally low temperature—uncomplicated by photons energized by a corona of hot electrons—more consistent with the expected appearance of an accreting intermediate-mass black hole3, 4. Here we report optical spectroscopic monitoring of M 101 ULX-1. We confirm the previous suggestion8 that the system contains a Wolf-Rayet star, and reveal that the orbital period is 8.2 days. The black hole has a minimum mass of 5 , and more probably a mass of 20 −30 , but we argue that it is very unlikely to be an intermediate-mass black hole. Therefore, its exceptionally soft spectra at high Eddington ratios violate the expectations for accretion onto stellar-mass black holes9, 10, 11. Accretion must occur from captured stellar wind, which has hitherto been thought to be so inefficient that it could not power an ultraluminous source12, 13.

What's So Special About Science (And How Much Should We Spend on It?)

What's So Special About Science (And How Much Should We Spend on It?)

William H. Press
Science, 15 November 2013: Vol. 342 no. 6160 pp. 817-822 DOI: 10.1126/science.342.6160.817

Scientific research probes the deepest mysteries of the universe and of living things, and it creates applications and technologies that benefit humanity and create wealth. This “Beauty and Benefits of Science” is the theme of this 2013 AAAS Annual Meeting.

The subject of my address is a different kind of mystery, although it is also related to this theme. It is the mystery of why society is willing to support an endeavor as abstract and altruistic as basic scientific research and an enterprise as large and practical as the research and development (R&D) enterprise as a whole. Put differently, it is the mystery that a unified scientific enterprise can be simultaneously the seed corn for economic advance and the confectionary corn syrup of pure, curiosity-driven scientific discovery.

A Mixture of Ancient and Modern Understanding Concerning the Distance and Motion of the Moon

Ptolemy's model of the Moon's motion implied that its distance varies by nearly a factor of two, implying that its angular size should also vary by nearly a factor of two. We present an analysis of 100 naked eye observations of the Moon's angular size obtained over 1145 days, showing regular variations of at least 3 arc minutes. Thus, ancient astronomers could have shown that a key implication of Ptolemy's model was wrong. In modern times we attribute the variation of distance of the Moon to the combined effect of the ellipticity of the Moon's orbit and the perturbing effect of the Sun on the Earth-Moon system. We show graphically how this affects the ecliptic longitudes and radial distance of the Moon. The longitude and distance "anomalies" are correlated with the Moon's phase. This is illustrated without any complex equations or geometry.

Majority is not Enough: Bitcoin Mining is Vulnerable


The Bitcoin cryptocurrency records its transactions in a public log called the blockchain. Its security rests critically on the distributed protocol that maintains the blockchain, run by participants called miners. Conventional wisdom asserts that the protocol is incentive compatible and secure against colluding minority groups, i.e., it incentivizes miners to follow the protocol as prescribed. We show that the Bitcoin protocol is not incentive- compatible. We present an attack with which colluding miners obtain a revenue larger than their fair share. This attack can have significant consequences for Bitcoin: Rational miners will prefer to join the selfish miners, and the colluding group will increase in size until it becomes a majority. At this point, the Bitcoin system ceases to be a decentralized currency.
Selfish mining is feasible for any group size of colluding miners. We propose a practical modification to the Bitcoin protocol that protects against selfish mining pools that command less than 1/4 of the resources. This threshold is lower than the wrongly assumed 1/2 bound, but better than the current reality where a group of any size can compromise the system.

Prevalence of Earth-size planets orbiting Sun-like stars

X-rays top space agenda

European agency selects mission themes, with X-ray telescope the biggest winner.

Attractive photons in a quantum nonlinear medium

Super-luminous supernovae on the rise

New observations suggest that certain extremely bright supernovae are not the nuclear explosions of very massive stars. Instead, they may be ordinary-mass events lit up by a potent central fountain of magnetic energy.

Why does a beer bottle foam up after a sudden impact on its mouth?

A sudden vertical impact on the mouth of a beer bottle generates a compression wave that propagates through the glass towards the bottom. When this wave reaches the base of the bottle, it is transmitted to the liquid as an expansion wave that travels to free surface, where it bounces back as a compression wave. This train of expansion-compression waves drives the forced cavitation of existing air pockets, leading to their violent collapse. A cloud of very small daughter bubbles are generated upon these collapses, that expand much faster than their mothers due to their smaller size. These rapidly growing bubble clusters effectively act as buoyancy sources, what leads to the formation of bubble-laden plumes whose void fraction increases quickly by several orders of magnitude, eventually turning most of the liquid into foam.

First results from the LUX dark matter experiment at the Sanford Underground Research Facility



The Large Underground Xenon (LUX) experiment, a dual-phase xenon time-projection chamber operating at the Sanford Underground Research Facility (Lead, South Dakota), was cooled and filled in February 2013. We report results of the first WIMP search dataset, taken during the period April to August 2013, presenting the analysis of 85.3 live-days of data with a fiducial volume of 118 kg. A profile-likelihood analysis technique shows our data to be consistent with the background-only hypothesis, allowing 90% confidence limits to be set on spin-independent WIMP-nucleon elastic scattering with a minimum upper limit on the cross section of 7.6 × 10^−46 cm^2 at a WIMP mass of 33 GeV/c^2. We find that the LUX data are in strong disagreement with low-mass WIMP signal interpretations of the results from several recent direct detection experiments.

Gauge-Gravity Duality and the Black Hole Interior

Donald Marolf*
Department of Physics, University of California, Santa Barbara, California 93106-9530, USA

Joseph Polchinski
Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106-4030, USA

 Received 18 July 2013; published 21 October 2013

See accompanying Physics Viewpoint

We present a further argument that typical black holes with field theory duals have firewalls at the horizon. This argument makes no reference to entanglement between the black hole and any distant system, and so is not evaded by identifying degrees of freedom inside the black hole with those outside. We also address the Einstein-Rosen=Einstein-Podolsky-Rosen conjecture of Maldacena and Susskind, arguing that the correlations in generic highly entangled states cannot be geometrized as a smooth wormhole.

Gamma-ray constraints on dark-matter annihilation to electroweak gauge and Higgs bosons

Gamma-ray constraints on dark-matter annihilation to electroweak gauge and Higgs bosons

Michael A. Fedderke, Edward W. Kolb, Tongyan Lin, Lian-Tao Wang

Dark-matter annihilation into electroweak gauge and Higgs bosons results in γ-ray emission. We use observational upper limits on the fluxes of both line and continuum γ-rays from the Milky Way Galactic Center and from Milky Way dwarf companion galaxies to set exclusion limits on allowed dark-matter masses. (Generally, Galactic Center γ-ray line search limits from the Fermi-LAT and the H.E.S.S. experiments are most restrictive.) Our limits apply under the following assumptions: a) the dark matter species is a cold thermal relic with present mass density equal to the measured dark-matter density of the universe; b) dark-matter annihilation to standard-model particles is described in the non-relativistic limit by a single effective operator O∝JDM⋅JSM, where JDM is a standard-model singlet current consisting of dark-matter fields (Dirac fermions or complex scalars), and JSM is a standard-model singlet current consisting of electroweak gauge and Higgs bosons; and c) the dark-matter mass is in the range 5 GeV to 20 TeV. We consider, in turn, the 34 possible operators with mass dimension 8 or lower with non-zero s-wave annihilation channels satisfying the above assumptions. Our limits are presented in a large number of figures, one for each of the 34 possible operators; these limits can be grouped into 13 classes determined by the field content and structure of the operators. We also identify three classes of operators (coupling to the Higgs and SU(2)L gauge bosons) that can supply a 130 GeV line with the desired strength to fit the putative line signal in Fermi data, while saturating the relic density and satisfying all other indirect constraints we consider.

Slowly fading super-luminous supernovae that are not pair-instability explosions

Pair instability supernovae or weird coupling of a SN and a magnetar?

Journal group for the Anton Pannekoek

Let's try if this works.

Spoof paper reveals little or no scrutiny at many open-access journals

Who's afraid of peer review?

by John Bohannon

Science,  4 October 2013,  Vol. 342 no. 6154 pp. 60-65  (DOI: 10.1126/science.342.6154.6)

... I created a scientific version of Mad Libs. The paper took this form: Molecule X from lichen species Y inhibits the growth of cancer cell Z. To substitute for those variables, I created a database of molecules, lichens, and cancer cell lines and wrote a computer program to generate hundreds of unique papers. ...

A spoof paper concocted by Science reveals little or no scrutiny at many open-access journals.

(Bonus: accompanying infographic by Randall Munroe.)


Swings between rotation and accretion power in a binary millisecond pulsar

Black-Hole Bombs and Photon-Mass Bounds [arXiv gr-qc]

Black-Hole Bombs and Photon-Mass Bounds (Pani P., et al.)

Generic extensions of the standard model predict the existence of ultralight bosonic degrees of freedom. Several ongoing experiments are aimed at detecting these particles or constraining their mass range. Here we show that massive vector fields around rotating black holes can give rise to a strong superradiant instability which extracts angular momentum from the hole. The observation of supermassive spinning black holes imposes limits on this mechanism. We show that current supermassive black hole spin estimates provide the tightest upper limits on the mass of the photon (mv<4x10^{-20} eV according to our most conservative estimate), and that spin measurements for the largest known supermassive black holes could further lower this bound to mv<10^{-22} eV. Our analysis relies on a novel framework to study perturbations of rotating Kerr black holes in the slow-rotation regime, that we developed up to second order in rotation, and that can be extended to other spacetime metrics and other theories.

The Muon Anomalous Magnetic Moment and the Pion Polarizability

What is next for the Kepler mission?

White papers have been released by NASA into what type of mission Kepler can pursue with only two working reaction wheels. It would be interesting to discuss some of the more realistic and far-out-there options open to Kepler!

Full details are at:

A good summary of some of the ideas is provided at:

Periastron Advance in Spinning Black Hole Binaries: Comparing Effective-One-Body and Numerical Relativity

Authors: Tanja Hinderer, Alessandra Buonanno, Abdul H. Mroué, Daniel A. Hemberger, Geoffrey Lovelace, Harald P. Pfeiffer

We compute the periastron advance using the effective-one-body formalism for binary black holes moving on quasi-circular orbits and having spins collinear with the orbital angular momentum. We compare the predictions with the periastron advance recently computed in accurate numerical-relativity simulations and find remarkable agreement for a wide range of spins and mass ratios. These results do not use any numerical-relativity calibration of the effective-one-body model, and stem from two key ingredients in the effective-one-body Hamiltonian: (i) the mapping of the two-body dynamics of spinning particles onto the dynamics of an effective spinning particle in a (deformed) Kerr spacetime, fully symmetrized with respect to the two-body masses and spins, and (ii) the resummation, in the test-particle limit, of all post-Newtonian (PN) corrections linear in the spin of the particle. In fact, even when only the leading spin PN corrections are included in the effective-one-body spinning Hamiltonian but all the test-particle corrections linear in the spin of the particle are resummed we find very good agreement with the numerical results (within the numerical error for equal-mass binaries and discrepancies of at most 1% for larger mass ratios). Furthermore, we specialize to the extreme mass-ratio limit and derive, using the equations of motion in the gravitational skeleton approach, analytical expressions for the periastron advance, the meridional Lense-Thirring precession and spin precession frequency in the case of a spinning particle on a nearly circular equatorial orbit in Kerr spacetime, including also terms quadratic in the spin.

Periastron Advance in Spinning Black Hole Binaries: Gravitational Self-Force from Numerical Relativity

Authors: Alexandre Le Tiec, Alessandra Buonanno, Abdul H. Mroué, Harald P. Pfeiffer, Daniel A. Hemberger, Goeffrey Lovelace

We study the general relativistic periastron advance in spinning black hole binaries on quasi-circular orbits, with spins aligned or anti-aligned with the orbital angular momentum, using numerical-relativity simulations, the post-Newtonian approximation, and black hole perturbation theory. By imposing a symmetry by exchange of the bodies' labels, we devise an improved version of the perturbative result, and use it as the leading term of a new type of expansion in powers of the symmetric mass ratio. This allows us to measure, for the first time, the gravitational self-force effect on the periastron advance of a non-spinning particle orbiting a Kerr black hole of mass M and spin S = -0.5 M^2, down to separations of order 9M. Comparing the predictions of our improved perturbative expansion with the exact results from numerical simulations of equal-mass and equal-spin binaries, we find a remarkable agreement over a wide range of spins and orbital separations.

Community ideas for Two-Wheel Kepler Missions

Paperscape Map

Paperscape is a tool to visualise the arXiv, an open, online repository for scientific research papers. The Paperscape map currently includes all (non-withdrawn) papers from the arXiv and is updated daily.

Each paper in the map is represented by a circle, with the area of the circle proportional to the number of citations that paper has. In laying out the map, an N-body algorithm is run to determine positions based on references between the papers. There are two “forces” involved in the N-body calculation: each paper is repelled from all other papers using an anti-gravity inverse-distance force, and each paper is attracted to all of its references using a spring modelled by Hooke’s law. We further demand that there is no overlap of the papers.

The map is rendered simply as a solid circle for each paper. The colour of the circle denotes the arXiv category of the paper, and the brightness indicates age. Brightness is sometime difficult to discern, and we are working on adding a heat-map overlay to indicate clearly the areas of the map which have the most recent activity.

As you zoom in on the map labels will start to appear on individual papers. These labels are (mostly) automatically extracted by analysing word frequency in the title and abstract of the paper, and are generally indicative of the subject matter of that paper. Zooming in closer also shows the author(s) of the paper. If a paper is deemed to be a review paper, or a set of lectures, this is noted.

References (and citation counting) are extracted by processing the TeX/LaTeX and PDF source obtained from the arXiv. This is done automatically each morning, and the map is finished updating about 3 or 4 hours after the arXiv’s new listing is announced. Some categories (noticeably hep-th and hep-ph) have better reference extraction than others and so the map for these areas has more variation in paper size and more structure. We are working on improving the reference extraction.

Astrobetter Ethics and Diversity Poll

C. Casey (IfA, U. Hawaii)  & K. Sheth (NRAO)

"The culture of academia can be rife with uncomfortable situations, some more clearcut than others.  We all began our research careers with expectations that both ourselves and our colleagues will behave ethically. Sometimes reality might be surprising.  Your judgement might be very different than your colleague’s down the hall due to cultural differences, the different subfields you work in, or different experiences in your careers.  Your own behavior might also evolve over the course of your career."

"Below, we have collated 25 hypothetical scenarios that astronomers might face in their careers and we’re going to ask you to rank them on a continuous scale from 1 to 9 (1=bad, 9=good).  [...]  The results of this survey will be collated and shared in another post in two weeks’ time.  [...]  If you are struggling to figure out who to evaluate in each scenario that’s fine. We left several purposefully ambiguous and only ask that you evaluate your level of comfort with the situation. [...]  These are intended to lead to broader discussion within a group."

Rainbow Colo(u)r Map (Still) Consider Harmful

Following our discussion today about colour maps, this is an interesting paper that discusses way we should not (in some cases) use colour maps. It is a short paper published by IEEE computer society but its analysis is applicable to astronomy. Mike Wheatland and Stuart Gilchrist were the people that pointed out this paper to me earlier in the year.



Determination of the intrinsic Luminosity Time Correlation in the X-ray Afterglows of GRBs

Gamma-ray bursts (GRBs), which have been observed up to redshifts z approx 9.5 can be good probes of the early universe and have the potential of testing cosmological models. The analysis by Dainotti of GRB Swift afterglow lightcurves with known redshifts and definite X-ray plateau shows an anti-correlation between the rest frame time when the plateau ends (the plateau end time) and the calculated luminosity at that time (or approximately an anti-correlation between plateau duration and luminosity). We present here an update of this correlation with a larger data sample of 101 GRBs with good lightcurves. Since some of this correlation could result from the redshift dependences of these intrinsic parameters, namely their cosmological evolution we use the Efron-Petrosian method to reveal the intrinsic nature of this correlation. We find that a substantial part of the correlation is intrinsic and describe how we recover it and how this can be used to constrain physical models of the plateau emission, whose origin is still unknown. The present result could help clarifing the debated issue about the nature of the plateau emission.



Who Will Pay for Public Access to Research Data?

Who Will Pay for Public Access to Research Data?
Francine Berman, Vint Cerf

On 22 February, the U.S. Office of Science and Technology Policy (OSTP) released a memo calling for public access for publications and data resulting from federally sponsored research grants (1). The memo directed federal agencies with more than $100 million R&D expenditures to “develop a plan to support increased public access to the results of research funded by the Federal Government.” Perhaps even more succinctly, a subsequent New York Times opinion page sported the headline “We Paid for the Research, So Let's See It” (2). So who pays for data infrastructure?

See also this New York Time piece.

The Sound of a Fermi Gamma-ray Burst

Gamma rays from GRB 080916C collected by the Fermi Large Area Telescope and converted into music.

Formation of sharp eccentric rings in debris disks with gas but without planets

Formation of sharp eccentric rings in debris disks with gas but without planets
Authors: W. Lyra & M. Kuchner
Nature, 499, 184–187 (11 July 2013), doi:10.1038/nature12281

‘Debris disks’ around young stars (analogues of the Kuiper Belt in our Solar System) show a variety of non-trivial structures attributed to planetary perturbations and used to constrain the properties of those planets. However, these analyses have largely ignored the fact that some debris disks are found to contain small quantities of gas, a component that all such disks should contain at some level. Several debris disks have been measured with a dust-to-gas ratio of about unity, at which the effect of hydrodynamics on the structure of the disk cannot be ignored. Here we report linear and nonlinear modelling that shows that dust–gas interactions can produce some of the key patterns attributed to planets. We find a robust clumping instability that organizes the dust into narrow, eccentric rings, similar to the Fomalhaut debris disk. The conclusion that such disks might contain planets is not necessarily required to explain these systems.

Subject terms: Exoplanets, Computational astrophysics

Related? "Sharp eccentric rings in planetless hydrodynamical models of debris disks", Lyra & Kuchner, ArXiv:1204.6322.


Recent combined observations from the first three years of Interstellar Boundary Explorer (IBEX) data allow us to examine the heliosphere's downwind region—the heliotail—for the first time. In contrast to a preliminary identification of a narrow "offset heliotail" structure, we find a broad slow solar wind plasma sheet crossing essentially the entire downwind side of the heliosphere at low to mid-latitudes, with fast wind tail regions to the north and south. The slow wind plasma sheet exhibits the steepest ENA spectra in the IBEX sky maps, appears as a two-lobed structure (lobes on the port and starboard sides), and is twisted in the sense of (but at a smaller angle than) the external magnetic field. The overall heliotail structure clearly demonstrates the intermediate nature of the heliosphere's interstellar interaction, where both the external dynamic and magnetic pressures strongly affect the heliosphere.

Candy Wrapper for the Earth's Inner Core

Observation of the Dependence of Scintillation from Nuclear Recoils in Liquid Argon on Drift Field

STARS SONGS - From X-Rays to Music

This is a story of how cosmic x-rays became music. A first step turned x-rays emitted by the binary system of EX Hydrae into sounds. A second step made these sounds into music.

Japanese astronomers revealed the origin of the cosmic background light

Researchers from Kyoto University, using the Atacama Large Millimeter/ submillimeter Array (ALMA) revealed that approximately 80% of the unidentified millimeter wave light from the Universe is actually emitted from galaxies.

Monday Colloquium Club - John Vaillancourt

Here are his suggested readings:

Hi Srikar

I would suggest the following 2 papers (note both have astroph links):

``Observations of Polarized Dust Emission in the Far-infrared to Millimeter''
J. E. Vaillancourt, 2012, in ASP Conf. Ser. 449, Astronomical Polarimetry 2008, ed. P. Bastien, 169

"Submillimeter Polarization of Galactic Clouds: A Comparison of 350μm and 850μm Data"
J. E. Vaillancourt & B. C. Matthews, 2012, ApJS, 201, 13

Cheers, John

Martian Fluvial Conglomerates at Gale Crater

Martian Fluvial Conglomerates at Gale Crater

R. M. E. Williams et al.

Science 31 May 2013: Vol. 340 no. 6136 pp. 1068-1072

Observations by the Mars Science Laboratory Mast Camera (Mastcam) in Gale crater reveal isolated outcrops of cemented pebbles (2 to 40 millimeters in diameter) and sand grains with textures typical of fluvial sedimentary conglomerates. Rounded pebbles in the conglomerates indicate substantial fluvial abrasion. ChemCam emission spectra at one outcrop show a predominantly feldspathic composition, consistent with minimal aqueous alteration of sediments. Sediment was mobilized in ancient water flows that likely exceeded the threshold conditions (depth 0.03 to 0.9 meter, average velocity 0.20 to 0.75 meter per second) required to transport the pebbles. Climate conditions at the time sediment was transported must have differed substantially from the cold, hyper-arid modern environment to permit aqueous flows across several kilometers.


NASA's Fermi, Swift See 'Shockingly Bright' Burst (GRB 130427A)

See also Fermi-LAT GCN Circulars for further details regarding the GeV emission

Dark Matter Search Results Using the Silicon Detectors of CDMS II

We report results of a search for Weakly Interacting Massive Particles (WIMPs) with the silicon (Si) detectors of the CDMS II experiment. A blind analysis of data from eight Si detectors, with a total raw exposure of 140.2 kg-days, revealed three WIMP-candidate events with a final surface-event background estimate of 0.41 (-0.08 +0.20)(stat.) (-0.24 +0.28) (syst.). Other known backgrounds from neutrons and 206Pb are limited to < 0.13 and < 0.08 events at the 90% confidence level, respectively. These data place a 90% upper confidence limit on the WIMP-nucleon cross section of 2.4E-41 cm^2 at a WIMP mass of 10 GeV/c^2. Simulations indicate a 5.4% probability that a statistical fluctuation of the known backgrounds would produce three or more events in the signal region. A profile likelihood ratio test that includes the measured recoil energies of the three events gives a 0.19% probability for the known-background-only hypothesis when tested against the alternative WIMP+background hypothesis. The highest likelihood was found for a WIMP mass of 8.6 GeV/c^2 and WIMP-nucleon cross section of 1.9E-41 cm^2.

Proposed new NSF grant approval guidelines

U.S. Lawmaker Proposes New Criteria for Choosing NSF Grants

The new chairman of the House science committee has drafted a bill that, in effect, would replace peer review at the National Science Foundation (NSF) with a set of funding criteria chosen by Congress. For good measure, it would also set in motion a process to determine whether the same criteria should be adopted by every other federal science agency.

In effect, the proposed bill would force NSF to adopt three criteria in judging every grant. Specifically, the draft would require the NSF director to post on NSF's website, prior to any award, a declaration that certifies the research is:

1) "…in the interests of the United States to advance the national health, prosperity, or welfare, and to secure the national defense by promoting the progress of science;

2) "… the finest quality, is groundbreaking, and answers questions or solves problems that are of utmost importance to society at large; and

3) "…not duplicative of other research projects being funded by the Foundation or other Federal science agencies."

NSF's current guidelines ask reviewers to consider the "intellectual merit" of a proposed research project as well as its "broader impacts" on the scientific community and society.


Life Before Earth

Alexei A. SharovRichard Gordon

(Submitted on 28 Mar 2013)

An extrapolation of the genetic complexity of organisms to earlier times suggests that life began before the Earth was formed. Life may have started from systems with single heritable elements that are functionally equivalent to a nucleotide. The genetic complexity, roughly measured by the number of non-redundant functional nucleotides, is expected to have grown exponentially due to several positive feedback factors: gene cooperation, duplication of genes with their subsequent specialization, and emergence of novel functional niches associated with existing genes. Linear regression of genetic complexity on a log scale extrapolated back to just one base pair suggests the time of the origin of life 9.7 billion years ago. This cosmic time scale for the evolution of life has important consequences: life took ca. 5 billion years to reach the complexity of bacteria; the environments in which life originated and evolved to the prokaryote stage may have been quite different from those envisaged on Earth; there was no intelligent life in our universe prior to the origin of Earth, thus Earth could not have been deliberately seeded with life by intelligent aliens; Earth was seeded by panspermia; experimental replication of the origin of life from scratch may have to emulate many cumulative rare events; and the Drake equation for guesstimating the number of civilizations in the universe is likely wrong, as intelligent life has just begun appearing in our universe. Evolution of advanced organisms has accelerated via development of additional information-processing systems: epigenetic memory, primitive mind, multicellular brain, language, books, computers, and Internet. As a result the doubling time of complexity has reached ca. 20 years. Finally, we discuss the issue of the predicted technological singularity and give a biosemiotics perspective on the increase of complexity.

Dark Matter Search Results Using the Silicon Detectors of CDMS II


We report results of a search for Weakly Interacting Massive Particles (WIMPs) with the silicon
(Si) detectors of the CDMS II experiment. A blind analysis of data from eight Si detectors, with
a total raw exposure of 140.2 kg-days, revealed three WIMP-candidate events with a final surface-
event background estimate of 0.41+0.20 (stat.)+0.28 (syst.). Other known backgrounds from neutrons
−0.08       −0.24
and 206 Pb are limited to < 0.13 and < 0.08 events at the 90% confidence level, respectively. These
data place a 90% upper confidence limit on the WIMP-nucleon cross section of 2.4 × 10−41 cm2 at a
WIMP mass of 10 GeV/c2 . Simulations indicate a 5.4% probability that a statistical fluctuation of
the known backgrounds would produce three or more events in the signal region. A profile likelihood
ratio test that includes the measured recoil energies of the three events gives a 0.19% probability
for the known-background-only hypothesis when tested against the alternative WIMP+background
hypothesis. The highest likelihood was found for a WIMP mass of 8.6 GeV/c2 and WIMP-nucleon
cross section of 1.9×10−41 cm2 .

Astropy v0.2: The First Release of the Community Built Astronomy Python Package


The aim of the project is to co-ordinate the Python code development efforts in Astronomy so as to be able to present users with a coherent set of tools to perform their work.

On February 20th, we released the first public version, Astropy v0.2! This was the culmination of a year and a half of hard work, with contributions from over 30 developers. It was the biggest milestone of the project so far, and we are now looking forward to hearing from the community, fixing any issues, and adding new components and features.

The current release already contains the following functionality:

Astropy also includes a lot of infrastructure code that makes it very easy for users to develop their own Astronomy packages, using Astropy as a core dependency.

Astropy integrates PyFITS, PyWCS, asciitable, and vo.table as sub-packages. Each of these are being phased-out as standalone packages. We encourage users to migrate to using Astropy instead of these standalone packages as most development efforts are being concentrated on the integrated functionalities within Astropy: the project isn’t just about creating new code, but also avoiding duplicated efforts and ultimately reducing the number of packages that Astronomers have to search for and install.

First Result from the Alpha Magnetic Spectrometer Experiment

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8×106 positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼250  GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

Planck 2013 Results

Planck 2013 Results Papers are out today: 

Voyager 1 Exits Solar System

"Recent Voyager 1 data indicate that on August 25, 2012 at a distance of
121.7 AU from the Sun, sudden and unprecedented intensity changes were
observed in anomalous and galactic cosmic rays"

Jose Canseco's theory of gravitation

Three Classes of Newtonian Three-Body Planar Periodic Orbits

Milovan ŠuvakovV. Dmitrašinović

(Submitted on 1 Mar 2013)

We present the results of a numerical search for periodic orbits of three equal masses moving in a plane under the influence of Newtonian gravity, with zero angular momentum. A topological method is used to classify periodic three-body orbits into families, which fall into four classes, with all three previously known families belonging to one class. The classes are defined by the orbits geometric and algebraic symmetries. In each class we present a few orbits initial conditions, 15 in all; 13 of these correspond to distinct orbits.

Related article from ScienceNOW:

Measuring the Universe More Accurately Than Ever Before


After nearly a decade of careful observations an international team of astronomers has measured the distance to our neighbouring galaxy, the Large Magellanic Cloud, more accurately than ever before. This new measurement also improves our knowledge of the rate of expansion of the Universe — the Hubble Constant — and is a crucial step towards understanding the nature of the mysterious dark energy that is causing the expansion to accelerate. The team used telescopes at ESO’s La Silla Observatory in Chile as well as others around the globe. These results appear in the 7 March 2013 issue of the journal Nature:

The arrow of time and the nature of spacetime George F R Ellis


This paper extends the work of a previous paper [arXiv:1108.5261] on top-down causation and quantum physics, to consider the origin of the arrow of time. It proposes that a `past condition' cascades down from cosmological to micro scales, being realized in many microstructures and setting the arrow of time at the quantum level by top-down causation. This physics arrow of time then propagates up, through underlying emergence of higher level structures, to geology, astronomy, engineering, and biology. The appropriate space-time picture to view all this is an emergent block universe (`EBU'), that recognizes the way the present is different from both the past and the future. This essential difference is the ultimate reason the arrow of time has to be the way it is.

A rapidly spinning supermassive black hole at the centre of NGC 1365

Broad X-ray emission lines from neutral and partially ionized iron observed in active galaxies have been interpreted as fluorescence produced by the reflection of hard X-rays off the inner edge of an accretion disk1, 2, 3, 4, 5, 6, 7. In this model, line broadening and distortion result from rapid rotation and relativistic effects near the black hole, the line shape being sensitive to its spin. Alternative models in which the distortions result from absorption by intervening structures provide an equally good description of the data8, 9, and there has been no general agreement on which is correct. Recent claims10 that the black hole11, 12 (2 × 106 solar masses) at the centre of the galaxy NGC 1365 is rotating at close to its maximum possible speed rest on the assumption of relativistic reflection. Here we report X-ray observations of NGC 1365 that reveal the relativistic disk features through broadened Fe-line emission and an associated Compton scattering excess of 10–30 kiloelectronvolts. Using temporal and spectral analyses, we disentangle continuum changes due to time-variable absorption from reflection, which we find arises from a region within 2.5 gravitational radii of the rapidly spinning black hole. Absorption-dominated models that do not include relativistic disk reflection can be ruled out both statistically and on physical grounds.

A sub-Mercury-sized exoplanet

T. Barclay et al.

Since the discovery of the first exoplanets, it has been known that other planetary systems can look quite unlike our own. Until fairly recently, we have been able to probe only the upper range of the planet size distribution, and, since last year, to detect planets that are the size of Earth or somewhat smaller. Hitherto, no planets have been found that are smaller than those we see in the Solar System. Here we report a planet significantly smaller than Mercury. This tiny planet is the innermost of three that orbit the Sun-like host star, which we have designated Kepler-37. Owing to its extremely small size, similar to that of the Moon, and highly irradiated surface, the planet, Kepler-37b, is probably rocky with no atmosphere or water, similar to Mercury.

The signature of proton acceleration in supernova remnants detected by Fermi

Detection of the Characteristic Pion-Decay Signature in Supernova Remnants

Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) are the sources of galactic cosmic rays, unequivocal evidence for the acceleration of protons in these objects is still lacking. When accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays. This offers a compelling way to detect the acceleration sites of protons. The identification of pion-decay gamma rays has been difficult because high-energy electrons also produce gamma rays via bremsstrahlung and inverse Compton scattering. We detected the characteristic pion-decay feature in the gamma-ray spectra of two SNRs, IC 443 and W44, with the Fermi Large Area Telescope. This detection provides direct evidence that cosmic-ray protons are accelerated in SNRs.

Energy release in the solar corona from spatially resolved magnetic braids

J. W. Cirtain1, L. Golub2, A. R. Winebarger1, B. De Pontieu3, K. Kobayashi4, R. L. Moore1, R. W. Walsh5, K. E. Korreck2, M. Weber2, P. McCauley2, A. Title3, S. Kuzin6 & C. E. DeForest7

It is now apparent that there are at least two heating mechanisms in the Sun’s outer atmosphere, or corona1–5. Wave heating may be the prevalent mechanism in quiet solar periods and may contribute to heating the corona to 1,500,000 K (refs 1–3). The active corona needs additional heating to reach 2,000,000–4,000,000 K; this heat has been theoretically proposed6–12 to come from the reconnection and unravelling of magnetic ‘braids’. Evidence favouring that pro- cess has been inferred13,14, but has not been generally accepted because observations are sparse and, in general, the braided mag- netic strands that are thought1–3,15–17 to have an angular width of about 0.2arc seconds have not been resolved10,18–20. Fine-scale braiding has been seen21,22 in the chromosphere but not, until now, in the corona. Here we report observations, at a resolution of 0.2 arc seconds, of magnetic braids in a coronal active region that are recon- necting, relaxing and dissipating sufficient energy to heat the struc- tures to about 4,000,000K. Although our 5-minute observations cannot unambiguously identify the field reconnection and sub- sequent relaxation as the dominant heating mechanism throughout active regions, the energy available

from the observed field relaxation in our example is ample for the observed heating.



Collective Motion of Moshers at Heavy Metal Concerts

Human collective behavior can vary from calm to panicked depending on social context. Using videos publicly available online, we study the highly energized collective motion of attendees at heavy metal concerts. We find these extreme social gatherings generate similarly extreme behaviors: a disordered gas-like state called a mosh pit and an ordered vortex-like state called a circle pit. Both phenomena are reproduced in flocking simulations demonstrating that human collective behavior is consistent with the predictions of simplified models.

Lawrence et al. Water Ice on Mars

Death and resurrection of the zeroth principle of thermodynamics

Synchronous X-ray and Radio Mode Switches: A Rapid Global Transformation of the Pulsar Magnetosphere

Synchronous X-ray and Radio Mode Switches: A Rapid Global Transformation of the Pulsar Magnetosphere

W. Hermsen, J. W. T. Hessels, L. Kuiper, et al.

Pulsars emit from low-frequency radio waves up to high-energy gamma-rays, generated anywhere from the stellar surface out to the edge of the magnetosphere. Detecting correlated mode changes across the electromagnetic spectrum is therefore key to understanding the physical relationship among the emission sites. Through simultaneous observations, we detected synchronous switching in the radio and x-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio-"bright" mode, the x-rays show only an unpulsed, nonthermal component. Conversely, when the pulsar is in a radio-"quiet" mode, the x-ray luminosity more than doubles and a 100% pulsed thermal component is observed along with the nonthermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories.

A precise and accurate determination of the cosmic microwave background temperature at z=0.89

S. Muller1, A. Beelen2, J. H. Black1, S. J. Curran3,4, C. Horellou1, S. Aalto1, F. Combes5, M. Gu´elin6,7, and
C. Henkel8,9

Context. According to the Big Bang theory and as a consequence of adiabatic expansion of the Universe, the temperature
of the cosmic microwave background (CMB) increases linearly with redshift. This relation is, however, poorly explored,
and detection of any deviation would directly lead to (astro-)physics beyond the standard model.
Aims. We aim at measuring the temperature of the CMB with an accuracy of a few percent at z=0.89 toward the
molecular absorber in the galaxy lensing the quasar PKS 1830−211.
Methods. We adopt a Monte-Carlo Markov Chain approach, coupled with predictions from the non-LTE radiative
transfer code RADEX, to solve the excitation of a set of various molecular species directly from their spectra.
Results. We determine TCMB=5.08±0.10 K at 68% confidence level. Our measurement is consistent with the value
TCMB=5.14 K predicted by the standard cosmological model with adiabatic expansion of the Universe. This is the most
precise determination of TCMB at z>0 to date.


Giant magnetized outflows from the centre of the Milky Way

Authors:  Ettore Carretti, Roland M. Crocker, Lister Staveley-Smith, Marijke Haverkorn, Cormac Purcell, B. M. Gaensler, Gianni Bernardi, Michael J. Kesteven & Sergio Poppi

Nature 493, 66–69 (03 January 2013)  doi:10.1038/nature11734

The nucleus of the Milky Way is known to harbour regions of intense star formation activity as well as a supermassive black hole1. Recent observations have revealed regions of γ-ray emission reaching far above and below the Galactic Centre (relative to the Galactic plane), the so-called ‘Fermi bubbles’2. It is uncertain whether these were generated by nuclear star formation or by quasar-like outbursts of the central black hole3, 4, 5, 6 and no information on the structures’ magnetic field has been reported. Here we report observations of two giant, linearly polarized radio lobes, containing three ridge-like substructures, emanating from the Galactic Centre. The lobes each extend about 60 degrees in the Galactic bulge, closely corresponding to the Fermi bubbles, and are permeated by strong magnetic fields of up to 15 microgauss. We conclude that the radio lobes originate in a biconical, star-formation-driven (rather than black-hole-driven) outflow from the Galaxy’s central 200 parsecs that transports a huge amount of magnetic energy, about 1055 ergs, into the Galactic halo. The ridges wind around this outflow and, we suggest, constitute a ‘phonographic’ record of nuclear star formation activity over at least ten million years.


A vast, thin plane of corotating dwarf galaxies orbiting the Andromeda galaxy

Authors:  Rodrigo A. Ibata, Geraint F. Lewis, Anthony R. Conn, Michael J. Irwin, Alan W. McConnachie, Scott C. Chapman, Michelle L. Collins, Mark Fardal, Annette M. N. Ferguson, Neil G. Ibata, A. Dougal Mackey, Nicolas F. Martin, Julio Navarro, R. Michael Rich, David Valls-Gabaud & Lawrence M. Widrow

Nature 493, 62–65  (03 January 2013)    doi:10.1038/nature11717

Dwarf satellite galaxies are thought to be the remnants of the population of primordial structures that coalesced to form giant galaxies like the Milky Way1. It has previously been suspected2 that dwarf galaxies may not be isotropically distributed around our Galaxy, because several are correlated with streams of H i emission, and may form coplanar groups3. These suspicions are supported by recent analyses4, 5, 6, 7. It has been claimed7 that the apparently planar distribution of satellites is not predicted within standard cosmology8, and cannot simply represent a memory of past coherent accretion. However, other studies dispute this conclusion9, 10, 11. Here we report the existence of a planar subgroup of satellites in the Andromeda galaxy (M 31), comprising about half of the population. The structure is at least 400 kiloparsecs in diameter, but also extremely thin, with a perpendicular scatter of less than 14.1 kiloparsecs. Radial velocity measurements12, 13, 14, 15 reveal that the satellites in this structure have the same sense of rotation about their host. This shows conclusively that substantial numbers of dwarf satellite galaxies share the same dynamical orbital properties and direction of angular momentum. Intriguingly, the plane we identify is approximately aligned with the pole of the Milky Way’s disk and with the vector between the Milky Way and Andromeda.

At Voyager 1 Starting on about August 25, 2012 at a Distance of 121.7 AU From the Sun, a Sudden Disappearance of Anomalous Cosmic Rays and an Unusually Large Sudden Increase of Galactic Cosmic Ray H and He Nuclei and Electron Occurred

At the Voyager 1 spacecraft in the outer heliosphere, after a series of complex intensity changes starting at about May 8th, the intensities of both anomalous cosmic rays (ACR) and galactic cosmic rays (GCR) changed suddenly and decisively on August 25th (121.7 AU from the Sun). The ACR started the intensity decrease with an initial e-folding rate of intensity decrease of ~1 day. Within a matter of a few days, the intensity of 1.9-2.7 MeV protons and helium nuclei had decreased to less than 0.1 of their previous value and after a few weeks, corresponding to the outward movement of V1 by ~0.1 AU, these intensities had decreased by factors of at least 300-500 and are now lower than most estimates of the GCR spectrum for these lower energies and also at higher energies. The decrease was accompanied by large rigidity dependent anisotropies in addition to the extraordinary rapidity of the intensity changes. Also on August 25th the GCR protons, helium and heavier nuclei as well as electrons increased suddenly with the intensities of electrons reaching levels ~30-50% higher than observed just one day earlier. This increase for GCR occurred over ~1 day for the lowest rigidity electrons, and several days for the higher rigidity nuclei of rigidity ~0.5-1.0 GV. After reaching these higher levels the intensities of the GCR of all energies from 2 to 400 MeV have remained essentially constant with intensity levels and spectra that may represent the local GCR. These intensity changes will be presented in more detail in this, and future articles, as this story unfolds.

Download PDF

How Einstein Discovered Dark Energy

(Submitted on 22 Nov 2012)

In 1917 Einstein published his Cosmological Considerations Concerning the General Theory of Relativity. In it was the first use of the cosmological constant. Shortly thereafter Schr\"odinger presented a note providing a solution to these same equations with the cosmological constant term transposed to the right hand side thus making it part of the stress-energy tensor. Einstein commented that if Schr\"odinger had something more than a mere mathematical convenience in mind he should describe its properties. Then Einstein detailed what some of these properties might be. In so doing, he gave the first description of Dark Energy. We present a translation of Schr\"odinger's paper and Einstein's response.

What do we want graduate school to be?

Astrobites recently conducted a reader survey, gathering responses about the '80-100 hours a week' e-mail.  The survey received more than 400 responses from undergraduates, graduate students, faculty, and researchers around the world.  Given the large sample size, the responses are quite interesting.

Binary Millisecond Pulsar Discovery via Gamma-Ray Pulsations

Millisecond pulsars, old neutron stars spun-up by accreting matter from a companion star, can reach high rotation rates of hundreds of revolutions per second. Until now, all such "recycled" rotation-powered pulsars have been detected by their spin-modulated radio emission. In a computing-intensive blind search of gamma-ray data from the Fermi Large Area Telescope (with partial constraints from optical data), we detected a 2.5-millisecond pulsar, PSR J1311−3430. This unambiguously explains a formerly unidentified gamma-ray source that had been a decade-long enigma, confirming previous conjectures. The pulsar is in a circular orbit with an orbital period of only 93 minutes, the shortest of any spin-powered pulsar binary ever found.

Is the solar system stable?

In this review Jacques Laskar reviews the question from Newton to Poincare to modern simulations using 154,000 polynomials and a million CPU hours. The inner solar system is known to exhibit chaotic behavior, which limits the amount of time we can run sims into the past or future. There is a 1% probability that Mercury's eccentricity could grow such that it collides with Venus, or Mars with the Earth.

Making the Moon from a Fast-Spinning Earth: A Giant Impact Followed by Resonant Despinning

Authors: Matija Ćuk and Sarah T. Stewart

From Science magazine, Wed Oct 17th, 2012

A common origin for the Moon and Earth is required by their identical isotopic composition. However, simulations of the current giant impact hypothesis for Moon formation find that most lunar material originated from the impactor, which should have had a different isotopic signature. Previous Moon-formation studies assumed that the angular momentum after the impact was similar to the present day; however, Earth-mass planets are expected to have higher spin rates at the end of accretion. Here, we show that typical last giant impacts onto a fast-spinning proto-Earth can produce a Moon-forming disk derived primarily from Earth's mantle. Furthermore, we find that a faster-spinning early Earth-Moon system can lose angular momentum and reach the present state through an orbital resonance between the Sun and Moon.

An Earth-mass planet orbiting alpha Centauri B

Xavier Dumusque,Francesco Pepe,Christophe Lovis,Damien Ségransan,Johannes Sahlmann,Willy Benz,François Bouchy,Michel Mayor,Didier Queloz,Nuno Santos& Stéphane Udry

Exoplanets down to the size of Earth have been found, but not in the habitable zone—that is, at a distance from the parent star at which water, if present, would be liquid. There are planets in the habitable zone of stars cooler than our Sun, but for reasons such as tidal locking and strong stellar activity, they are unlikely to harbour water–carbon life as we know it. The detection of a habitable Earth-mass planet orbiting a star similar to our Sun is extremely difficult, because such a signal is overwhelmed by stellar perturbations. Here we report the detection of an Earth-mass planet orbiting our neighbour star α Centauri B, a member of the closest stellar system to the Sun. The planet has an orbital period of 3.236 days and is about 0.04 astronomical units from the star (one astronomical unit is the Earth–Sun distance).

Astrobetter: "Not what we want"

Astrobetter links to a discussion of a letter that was purportedly sent out to the grad students of a astronomy department somewhere in the US.  I'm curious what people think about this and what it says about our community.

Best Practices for Scientific Computing

(Submitted on 1 Oct 2012)

Scientists spend an increasing amount of time building and using software. However, most scientists are never taught how to do this efficiently. As a result, many are unaware of tools and practices that would allow them to write more reliable and maintainable code with less effort. We describe a set of best practices for scientific software development that have solid foundations in research and experience, and that improve scientists' productivity and the reliability of their software.

PNAS study on gender bias in science faculty

paper is at:
NYT article:

2012 Ig Nobel Prize Winners

From the website: "The Ig Nobel Prizes honor achievements that first make people laugh, and then make them think. The prizes are intended to celebrate the unusual, honor the imaginative — and spur people's interest in science, medicine, and technology."


Click the link to see this years winners.

The United States must rejoin the SKA

Astronomy: The United States must rejoin the SKA
Anthony J. Beasley and Ethan J. Schreier

Nature 489, 363 (20 September 2012) doi:10.1038/489363a
Published online 19 September 2012

The world's most powerful astronomical instrument is currently being built in South Africa and Australia. A growing consortium of countries, soon to be marshalled by incoming director-general Phil Diamond, is laying the foundation for some unique science. When it comes online next decade, the Square Kilometre Array (SKA) will observe diffuse hydrogen ionized by the first stars and galaxies, use pulsars to explore general relativity, and detect the imprints of dark energy on the distribution of matter in the Universe.

There is one country notable by its absence in this endeavour: the United States. And its absence threatens to hinder the SKA's pursuit of its scientific goals. After nearly 20 years of participation, US astronomers last year dropped out of the SKA collaboration as the result of disillusionment with the project's planning process and budget pressure from the National Science Foundation (NSF). [...]

How the Scientific Community Reacts to Newly Submitted Preprints: Article Downloads, Twitter Mentions, and Citations

Production of Near-Earth Asteroids on Retrograde Orbits

S. Greenstreet1, B. Gladman1, H. Ngo2, M. Granvik3, and S. Larson4
ApJ 749 L39 doi:10.1088/2041-8205/749/2/L39

While computing an improved near-Earth object (NEO) steady-state orbital distribution model, we discovered in the numerical integrations the unexpected production of retrograde orbits for asteroids that had originally exited from the accepted main-belt source regions. Our model indicates that ~0.1% (a factor of two uncertainty) of the steady-state NEO population (perihelion q < 1.3 AU) is on retrograde orbits. These rare outcomes typically happen when asteroid orbits flip to a retrograde configuration while in the 3:1 mean-motion resonance with Jupiter and then live for ~0.001 to 100 Myr. The model predicts, given the estimated near-Earth asteroid (NEA) population, that a few retrograde 0.1-1 km NEAs should exist. Currently, there are two known MPC NEOs with asteroidal designations on retrograde orbits which we therefore claim could be escaped asteroids instead of devolatilized comets. This retrograde NEA population may also answer a long-standing question in the meteoritical literature regarding the origin of high-strength, high-velocity meteoroids on retrograde orbits.

The Encyclopedia of DNA Elements (ENCODE)

"2001 will always be remembered as the year of the human genome. The availability of its sequence transformed biology, and the exemplary way in which hundreds of researchers came together to form a public consortium paved the way for 'big science' in biology. It was an incredible achievement but it was always clear that knowing the 'code' was only the beginning. To understand how cells interpret the information locked within the genome much more needed to be learnt. This became the task of ENCODE, the Encyclopedia Of DNA Elements, the aim of which was to describe all functional elements encoded in the human genome. Nine years after launch, its main efforts culminate in the publication of 30 coordinated papers, 6 of which are in this issue of Nature.

Collectively, the papers describe 1,640 data sets generated across 147 different cell types. Among the many important results there is one that stands out above them all: more than 80% of the human genome's components have now been assigned at least one biochemical function. [...]"


News and Views:

On the reliability of stellar ages and age spreads inferred from pre-main-sequence evolutionary models

Review of presentation "On the reliability of stellar ages and age spreads inferred from pre-main-sequence evolutionary models" by Takashi Hosokawa.

See also


Kim will be leading the discussion on this ApJL article for this week's Adler journal club:;jsessionid=956F4D55B4694CF6F7A7F78E9F5667E4.c1

AST Portfolio Review

A radio pulsar with an 8.5-second period that challenges emission models

Young, Manchester, and Johnston 1999, Nature, 400, 848

Radio pulsars are rotating neutron stars that emit beams of radiowaves from regions above their magnetic poles. Popular theories of the emission mechanism require continuous electron–positron pair production, with the potential responsible for accelerating the particles being inversely related to the spin period. Pair production will stop when the potential drops below a threshold, so the models predict that radio emission will cease when the period exceeds a value that depends on the magnetic field strength and configuration. Here we show that the pulsar J2144-3933, previously thought to have a period of 2.84 s, actually has a period of 8.51 s, which is by far the longest of any known radio pulsar. Moreover, under the usual model assumptions, based on the neutron-star equations of state, this slowly rotating pulsar should not be emitting a radio beam. Therefore either the model assumptions are wrong, or current theories of radio emission must be revised.

Complementarity or/and/not firewalls

Black holes: Complementarity or firewalls? (Almheiri, Marolf, Polchinski, Sully):
Complementarity and firewalls (Susskind):

Complementarity, not firewalls (Harlow):

Symmetry Restoration By Acceleration


The Higgs sector of the phenomenological MSSM in the light of the Higgs boson discovery

Infographic: Exoplanets

NRO gives NASA two unused spy satellites

‘Repurposed’ Telescope May Explore Secrets of Dark Energy

The phone call came like a bolt out of the blue, so to speak, in January of 2011. On the other end of the line was someone from the National Reconnaissance Office, which operates the nation’s fleet of spy satellites. They had some spare unused “hardware” to get rid of. Was NASA interested?

And so it was that when John Grunsfeld, the physicist and former astronaut, walked into his office a year later to start his new job as NASA’s associate administrator for space science, he discovered that his potential armada was a bit bigger than he knew. Sitting in a clean room in upstate New York were a pair of space telescopes the same size as the famed Hubble Space Telescope, but which had been built to point down at the Earth instead of up at the heavens.

Interesting new Theoretical Fluid Dynamics Results

Bubbles and vorticity.

Modified gravity as a common cause for cosmic acceleration and flat galaxy rotation curves

Generating matter inhomogeneities in general relativity

Alan Coley, Woei Chet Lim
(Submitted on 10 May 2012)
In this Letter we discuss a natural general relativistic mechanism that causes inhomogeneities and hence generates matter perturbations in the early universe. We concentrate on spikes, both incomplete spikes and recurring spikes, that naturally occur in the initial oscillatory regime of general cosmological models. In particular, we explicitly show that spikes occurring in a class of G_2 models lead to inhomogeneities that, due to gravitational instability, leave small residual imprints on matter in the form of matter perturbations. The residual matter overdensities from recurring spikes are not local but form on surfaces. We discuss the potential physical consequences of the residual matter imprints and their possible effect on the subsequent formation of large scale structure.

Cosmic Variance: Dark Matter vs. Modified Gravity

Dark Matter vs. Modified Gravity: A Trialogue

Superluminal Spin-1/2 Particles are Left-Handed: From the Gordon Decomposition to the Suppression of Right-Handed States


U. D. Jentschura, B. J. Wundt
(Submitted on 2 May 2012)
Superluminal spin-1/2 particles are analyzed under the assumption that the equation of motion is compatible with Lorentz invariance (tachyonic particles). It is found that tachyonic spin-1/2 particles can only be observed in left-handed helicity states, and that tachyonic spin-1/2 antiparticles are always right-handed. This result is independent of the numerical value of the tachyonic mass term, holds even for a tiny tachyonic mass of a few eV and may eventually be verified or falsified by experiments in the long-term future. We propose a superluminal character of the neutrino as an alternative explanation for the lack of a right-handed helicity state. This conclusion is connected with the superluminal Dirac algebra (Gordon identities) for spin-1/2 tachyonic particles. In particular, we derive the decomposition of the superluminal vector and axial vector current into convective and spin parts. Finally, we complement the discussion by giving bispinor solutions for generalized Dirac equations with mixed tachyonic and tardyonic mass terms, of the form m_1 + gamma5*m2, and m1 + i*gamma5*m2. These solutions and corresponding sums over the fundamental spinor solutions may be useful in a wider context.

On the dissipative non-minimal braneworld inflation

Kourosh Nozari, M. Shoukrani
(Submitted on 8 Apr 2012)
We study the effects of the non-minimal coupling on the dissipative dynamics of the warm inflation in a braneworld setup, where the inflaton field is non-minimally coupled to induced gravity on the warped DGP brane. We study with details the effects of the non-minimal coupling and dissipation on the inflationary dynamics on the normal DGP branch of this scenario in the high-dissipation and high-energy regime. We show that incorporation of the non-minimal coupling in this setup decreases the number of e-folds relative to the minimal case. We also compare our model parameters with recent observational data.

Road Signs for UV-Completion

pdf. Dvali, et al.

We confront the concepts of Wilsonian UV-completion versus self-completion by Classicalization in theories with derivatively-coupled scalars. We observe that the information about the UV-completion road is encoded in the sign of the derivative terms. We note that the sign of the derivative couplings for which there is no consistent Wilsonian UV-completion is the one that allows for consistent classicalons. This is an indication that for such a sign the vertex must be treated as fundamental and the theory self-protects against potential inconsistencies, such as superluminality, via self-completion by classicalization. Applying this reasoning to the UV-completion of the Standard Model, we see that the information about the Higgs versus classicalization is encoded in the sign of the scattering amplitude of longitudinal W-bosons. Negative sign excludes Higgs or any other weakly-coupled Wilsonian physics.

Star Formation newsletter April 22, 2012

Quantum Stability of Chameleon Field Theories

Amol Upadhye, Wayne Hu, Justin Khoury

Primordial non-Gaussianity from mixed inflaton-curvaton perturbations

José Fonseca, David Wands (ICG, Portsmouth)
(Submitted on 16 Apr 2012)
We characterise the primordial perturbations produced due to both inflaton and curvaton fluctuations in models where the curvaton has a quadratic, cosine or hyperbolic potential, and the inflaton potential is characterised by the usual slow-roll parameters. Isocurvature curvaton field perturbations can produce significant non-Gaussianity in the primordial density field, in contrast with adiabatic inflaton field perturbations which produce negligible non-Gaussianity for canonical scalar fields. A non-self-interacting curvaton with quadratic potential produces a local-type non-Gaussianity that is well described by the non-linearity parameter fNL, which may be scale-dependent when the inflaton perturbations dominate the power spectrum. We show how observational bounds on non-linearity parameters and the tensor-scalar ratio can be used to constrain curvaton and inflaton parameters. We find a consistency relation between the bispectrum and trispectrum parameters in a mixed inflaton-curvaton model for a quadratic curvaton potential. Self-interaction terms in the curvaton potential can lead to both a large trispectrum parameter, gNL, and scale-dependence of the non-linearity parameters.

Shining Light into Black Boxes

Shining Light into Black Boxes
A. Morin, J. Urban, P. D. Adams, I. Foster, A. Sali, D. Baker, P. Sliz

The publication and open exchange of knowledge and material form the backbone of scientific progress and reproducibility and are obligatory for publicly funded research. Despite increasing reliance on computing in every domain of scientific endeavor, the computer source code critical to understanding and evaluating computer programs is commonly withheld, effectively rendering these programs “black boxes” in the research work flow. Exempting from basic publication and disclosure standards such a ubiquitous category of research tool carries substantial negative consequences. Eliminating this disparity will require concerted policy action by funding agencies and journal publishers, as well as changes in the way research institutions receiving public funds manage their intellectual property (IP).

On Loops in Inflation II: IR Effects in Single Clock Inflation

In single clock models of inflation the coupling between modes of very different scales does not have any significant dynamical effect during inflation. It leads to interesting projection effects. Larger and smaller modes change the relation between the scale a mode of interest will appear in the post-inflationary universe and will also change the time of horizon crossing of that mode. We argue that there are no infrared projection effects in physical questions, that there are no effects from modes of longer wavelength than the one of interest. These potential effects cancel when computing fluctuations as a function of physically measurable scales. Modes on scales smaller than the one of interest change the mapping between horizon crossing time and scale. The correction to the mapping computed in the absence of fluctuations is enhanced by a factor N_e, the number of e-folds of inflation between horizon crossing and reheating. The new mapping is stochastic in nature but its variance is not enhanced by N_e.
Leonardo Senatore, Matias Zaldarriaga

On Loops in Inflation III: Time Independence of zeta in Single Clock Inflation

Studying loop corrections to inflationary perturbations, with particular emphasis on infrared factors, is important to understand the consistency of the inflationary theory, its predictivity and to establish the existence of the slow-roll eternal inflation phenomena and its recently found volume bound. In this paper we prove that the zeta correlation function is time-independent at one-loop level in single clock inflation. While many of the one-loop diagrams lead to a time-dependence when considered individually, the time-dependence beautifully cancels out in the overall sum. We identify two subsets of diagrams that cancel separately due to different physical reasons. The first cancellation is related to the change of the background cosmology due to the renormalization of the stress tensor. It results in a cancellation between the non-1PI diagrams and some of the diagrams made with quartic vertices. The second subset of diagrams that cancel is made up of cubic operators, plus the remaining quartic ones. We are able to write the sum of these diagrams as the integral over a specific three-point function between two very short wavelengths and one very long one. We then apply the consistency condition for this three-point function in the squeezed limit to show that the sum of these diagrams cannot give rise to a time dependence. This second cancellation is thus a consequence of the fact that in single clock inflation the attractor nature of the solution implies that a long wavelength zeta perturbation is indistinguishable from a trivial rescaling of the background, and so results in no physical effect on short wavelength modes.

Guilherme L. Pimentel, Leonardo Senatore, Matias Zaldarriaga

Issues Concerning Loop Corrections to the Primordial Power Spectra

We expound ten principles in an attempt to clarify the debate over infrared loop corrections to the primordial scalar and tensor power spectra from inflation. Among other things we note that existing proposals for nonlinear extensions of the scalar fluctuation field $\zeta$ introduce new ultraviolet divergences which no one understands how to renormalize. Loop corrections and higher correlators of these putative observables would also be enhanced by inverse powers of the slow roll parameter $\epsilon$. We propose an extension which should be better behaved.
S. P. Miao (Utrecht), R. P. Woodard (Florida)

Classical Duals, Legendre Transforms and the Vainshtein Mechanism

Classical and quantum massive cosmology for the open FRW universe

NASA Senior Review Out

Gods as Topological Invariants

(Submitted on 1 Apr 2012)

We show that the number of gods in a universe must equal the Euler characteristics of its underlying manifold. By incorporating the classical cosmological argument for creation, this result builds a bridge between theology and physics and makes theism a testable hypothesis. Theological implications are profound since the theorem gives us new insights in the topological structure of heavens and hells. Recent astronomical observations can not reject theism, but data are slightly in favor of atheism.

Comments: Please note that the publication date is April 1st 2012
Subjects: Popular Physics (physics.pop-ph); General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph); General Topology (math.GN)
MSC classes: 54-XX, 37C15, 20K45, 14J80
Cite as: arXiv:1203.6902v1 [physics.pop-ph]

Competition among memes in a world with limited attention

L. Weng, A. Flammini, A. Vespignani & F. Menczer
Scientific Reports 2, Article number: 335 doi:10.1038/srep00335
Received 19 September 2011 Accepted 08 March 2012 Published 29 March 2012

The wide adoption of social media has increased the competition among ideas for our finite attention. We employ a parsimonious agent-based model to study whether such a competition may affect the popularity of different memes, the diversity of information we are exposed to, and the fading of our collective interests for specific topics. Agents share messages on a social network but can only pay attention to a portion of the information they receive. In the emerging dynamics of information diffusion, a few memes go viral while most do not. The predictions of our model are consistent with empirical data from Twitter, a popular microblogging platform. Surprisingly, we can explain the massive heterogeneity in the popularity and persistence of memes as deriving from a combination of the competition for our limited attention and the structure of the social network, without the need to assume different intrinsic values among ideas

The Worldvolume Action of Kink Solitons in AdS Spacetime

the abstract

Universality of geometry

Quantum Gravity Constraints on Inflation

Spacetime Structure of the Black Hole Evaporation

Higgs and Dark Matter Hints of an Oasis in the Desert

Clifford Cheung, Michele Papucci, Kathryn M. Zurek

Massive Gravity Theories and limits of Ghost-free Bigravity models

Authors: Miguel F. Paulos, Andrew J. Tolley

Separable and non-separable multi-field inflation and large non-Gaussianity

In this paper we provide a general framework based on $\delta N$ formalism to estimate the cosmological observables pertaining to the cosmic microwave background radiation for non-separable potentials, and for generic \emph{end of inflation} boundary conditions. We provide analytical and numerical solutions to the relevant observables by decomposing the cosmological perturbations along the curvature and the isocurvature directions, \emph{instead of adiabatic and entropy directions}. We then study under what conditions large bi-spectrum and tri-spectrum can be generated through phase transition which ends inflation. In an illustrative example, we show that large $f_{NL}\sim {\cal O}(80)$ and $\tau_{NL}\sim {\cal O}(20000)$ can be obtained for the case of separable and non-separable inflationary potentials.

Anupam Mazumdar, Lingfei Wang

Multifield consequences for D-brane inflation

We analyse the multifield behaviour in D-brane inflation when contributions from the bulk are taken into account. For this purpose, we study a large number of realisations of the potential; we find the nature of the inflationary trajectory to be very consistent despite the complex construction. Inflation is always canonical and occurs in the vicinity of an inflection point. Extending the transport method to non-slow-roll and to calculate the running, we obtain distributions for observables. The spectral index is typically blue and the running positive, putting the model under moderate pressure from WMAP7 constraints. The local f_NL and tensor-to-scalar ratio are typically unobservably small, though we find approximately 0.5% of realisations to give observably large local f_NL. Approximating the potential as sum-separable, we are able to give fully analytic explanations for the trends in observed behaviour. Finally we find the model suffers from the persistence of isocurvature perturbations, which can be expected to cause further evolution of adiabatic perturbations after inflation. We argue this is a typical problem for models of multifield inflation involving inflection points and renders models of this type technically unpredictive without a description of reheating.

Mafalda Dias, Jonathan Frazer, Andrew R. Liddle

Landau-Ginzburg Limit of Black Hole's Quantum Portrait: Self Similarity and Critical Exponent

(Dvali, Gomez)

Recently we have suggested that the microscopic quantum description of a black hole is an overpacked self-sustained Bose-condensate of N weakly-interacting soft gravitons, which obeys the rules of 't Hooft's large-N physics. In this note we derive an effective Landau-Ginzburg Lagrangian for the condensate and show that it becomes an exact description in a semi-classical limit that serves as the black hole analog of 't Hooft's planar limit. The role of a weakly-coupled Landau-Ginzburg order parameter is played by N. This description consistently reproduces the known properties of black holes in semi-classical limit. Hawking radiation, as the quantum depletion of the condensate, is described by the slow-roll of the field N. In the semiclassical limit, where black holes of arbitrarily small size are allowed, the equation of depletion is self similar leading to a scaling law for the black hole size with critical exponent 1/3.

pdf link

Observation of electron-antineutrino disappearance at Daya Bay (hep-ex)

Measurement claim of non-zero θ_13 neutrino mixing angle.

Decoherence delays false vacuum decay

Cleaning up the cosmological constant

Ian Kimpton, Antonio Padilla

Biosignatures as revealed by spectropolarimetry of Earthshine

Low-resolution intensity spectra of Earth’s atmosphere obtained from space reveal strong signatures of life (‘biosignatures’), such as molecular oxygen and methane with abundances far from chemical equilibrium, as well as the presence of a ‘red edge’ (a sharp increase of albedo for wavelengths longer than 700 nm) caused by surface vegetation1. Light passing through the atmosphere is strongly linearly polarized by scattering (from air molecules, aerosols and cloud particles) and by reflection (from oceans and land2). Spectropolarimetric observations of local patches of Earth’s sky light from the ground contain signatures of oxygen, ozone and water, and are used to characterize the properties of clouds and aerosols34. When applied to exoplanets, ground-based spectropolarimetry can better constrain properties of atmospheres and surfaces than can standard intensity spectroscopy56789. Here we report disk-integrated linear polarization spectra of Earthshine, which is sunlight that has been first reflected by Earth and then reflected back to Earth by the Moon10111213. The observations allow us to determine the fractional contribution of clouds and ocean surface, and are sensitive to visible areas of vegetation as small as 10 per cent. They represent a benchmark for the diagnostics of the atmospheric composition, mean cloud height and surfaces of exoplanets.

Cosmological particle creation in the lab?

Does Collocation Inform the Impact of Collaboration?

Kyungjoon Lee, John S. Brownstein, Richard G. Mills, Isaac S. Kohane

It has been shown that large interdisciplinary teams working across geography are more likely to be impactful. We asked whether the physical proximity of collaborators remained a strong predictor of the scientific impact of their research as measured by citations of the resulting publications.

Methodology/Principal Findings
Articles published by Harvard investigators from 1993 to 2003 with at least two authors were identified in the domain of biomedical science. Each collaboration was geocoded to the precise three-dimensional location of its authors. Physical distances between any two coauthors were calculated and associated with corresponding citations. Relationship between distance of coauthors and citations for four author relationships (first-last, first-middle, last-middle, and middle-middle) were investigated at different spatial scales. At all sizes of collaborations (from two authors to dozens of authors), geographical proximity between first and last author is highly informative of impact at the microscale (i.e. within building) and beyond. The mean citation for first-last author relationship decreased as the distance between them increased in less than one km range as well as in the three categorized ranges (in the same building, same city, or different city). Such a trend was not seen in other three author relationships.

Despite the positive impact of emerging communication technologies on scientific research, our results provide striking evidence for the role of physical proximity as a predictor of the impact of collaborations.

Solving the Quantum Nonlocality Enigma by Weyl's Conformal Geometrodynamics

Decoupling Survives Inflation: A Critical Look at Effective Field Theory Violations During Inflation

Classical Duals of Derivatively Self-Coupled Theories
Gregory Gabadadze, Kurt Hinterbichler, David Pirtskhalava

Non-linear Realizations of Conformal Symmetry and Effective Field Theory for the Pseudo-Conformal Universe

Kurt Hinterbichler, Austin Joyce, Justin Khoury

Rotation period of Venus estimated from Venus Express VIRTIS images and Magellan altimetry

The 1.02 μm wavelength thermal emission of the nightside of Venus is strongly anti-correlated to the elevation of the surface. The VIRTIS instrument on Venus Express has mapped this emission and therefore gives evidence for the orientation of Venus between 2006 and 2008. The Magellan mission provided a global altimetry data set recorded between 1990 and 1992. Comparison of these two data sets reveals a deviation in longitude indicating that the rotation of the planet is not fully described by the orientation model recommended by the IAU. This deviation is sufficiently large to affect estimates of surface emissivity from infrared imaging. A revised period of rotation of Venus of 243.023 ± 0.002 d aligns the two data sets. This period of rotation agrees with pre-Magellan estimates but is significantly different from the commonly accepted value of 243.0185 ± 0.0001 d estimated from Magellan radar images. It is possible that this discrepancy stems from a length of day variation with the value of 243.023 ± 0.002 d representing the average of the rotation period over 16 years.

The Strong Multifield Slowroll Condition and Spiral Inflation

Casimir forces between cylinders at different temperatures

1202.0892 Testing modified gravity models with recent cosmological observations

Lorentz Invariance Violation in Modified Gravity 1202.0740

Philippe Brax

Analyzing Cosmic Bubble Collisions

Roberto Gobbetti, Matthew Kleban

Anomalies, boundaries and the in-in formalism

Zhiqi's new paper

Derivative Coupling paper

Effective theories of single field inflation when heavy fields matter

Authors: Ana Achucarro, Jinn-Ouk Gong, Sjoerd Hardeman, Gonzalo A. Palma, Subodh P. Patil

Successful Search for Ether Drift in a Modified Michelson-Morley Experiment Using the GPS

Authors: Stephan J.G. Gift
Ether drift resulting from the rotation of the Earth has been detected. This was accomplished using GPS technology in a modified Michelson-Morley experiment. The original Michelson-Morley experiment searched for ether drift by observing round-trip light travel time differences using interference fringe shifts. This method is limited by length contraction effects that significantly reduce any fringe shifts. In the modified approach elapsed time for one-way light transmission is directly determined using GPS clocks. The method yields travel time differences for light transmission in the East-West direction but not in the North-South direction consistent with rotationally-induced ether drift.
Comments: 12 Pages. Accepted for publication in Applied Physics Research

Can gravity distinguish between Dirac and Majorana Neutrinos?

Satellites around massive galaxies since z~2

Satellites around massive galaxies since z~2

(Submitted on 11 Jan 2012)

Accretion of minor satellites has been postulated as the most likely mechanism to explain the significant size evolution of the massive galaxies over cosmic time. Using a sample of 629 massive (Mstar~10^11 Msun) galaxies from the near-infrared Palomar/DEEP-2 survey, we explore which fraction of these objects has satellites with 0.01 Msat < Mcentral < 1 (1:100) up to z=1 and which fraction has satellites with 0.1 Msat < Mcentral < 1 (1:10) up to z=2 within a projected radial distance of 100 kpc. We find that the fraction of massive galaxies with satellites, after the background correction, remains basically constant and close to ~30% for satellites with a mass ratio down to 1:100 up to z=1, and ~15% for satellites with a 1:10 mass ratio up to z=2. The family of spheroid-like massive galaxies presents a 2-3 times larger fraction of objects with satellites than the group of disk-like massive galaxies. A crude estimation of the number of 1:3 mergers a massive spheroid-like galaxy experiences since z~2 is around 2. For a disk-like galaxy this number decreases to ~1.

An Astrophysical Peek into Einstein’s Static Universe: No Dark Energy

It is shown that in order that the fluid pressure and acceleration are uniform and finite in Einstein’s Static
Universe (ESU),  , the cosmological constant, is zero.  being a fundamental constant, should be the
same everywhere including the Friedman model. Independent proofs show that it must be so. Accordingly,
the supposed acceleration of the universe and the attendant concept of a “Dark Energy” (DE) could be an
illusion; an artifact of explaining cosmological observations in terms of an oversimplified model which is
fundamentally inappropriate. Indeed observations show that the actual universe is lumpy and inhomogeneous
at the largest scales. Further in order that there is no preferred centre, such an inhomogeneity might be ex-
pressed in terms of infinite hierarchial fractals. Also, the recent finding that the Friedman model intrinsically
corresponds to zero pressure (and hence zero temperature) in accordance with the fact that an ideal Hubble
flow implies no collision, no randomness (Mitra, Astrophys. Sp. Sc., 333,351, 2011) too shows that the
Friedman model cannot represent the real universe having pressure, temperature and radiation. Dark Energy
might also be an artifact of the neglect of dust absorption of distant Type 1a supernovae coupled with likely
evolution of supernovae luminosities or imprecise calibration of cosmic distance ladders or other systemetic
errors (White, Rep. Prog. Phys., 70, 883, 2007). In reality, observations may not rule out an inhomogeneous
static universe (Ellis, Gen. Rel. Grav. 9, 87, 1978), if the fundamental “constants” are indeed constant.

Self-consistent orbital evolution of a particle around a Schwarzschild black hole

The motion of a charged particle is influenced by the self-force arising from the particle's interaction with its own field. In a curved spacetime, this self-force depends on the entire past history of the particle and is difficult to evaluate. As a result, all existing self-force evaluations in curved spacetime are for particles moving along a fixed trajectory. Here, for the first time, we overcome this longstanding limitation and present fully self-consistent orbits and waveforms of a scalar charged particle around a Schwarzschild black hole.

Electric Currents Key to Magnetic Phenomena

Including the effects of electric currents in any description of the origin, shape, or motion of cosmic magnetized plasma is crucial for understanding many observed astronomical phenomena. The Maxwell (Heaviside) equations are based on real experimental measurements. These fundamental expressions clearly link electric current densities, magnetic flux densities, and electric fields into a unified conceptual whole. Examples are presented to demonstrate the pitfalls of omitting the contribution and effects of currents from descriptions of the behavior of magnetic fields. An example suggests a possible electrical explanation of the enigmatic cyclical reversal of magnetic polarities near sunspots and demonstrates the unique insight afforded by including the causal effects of currents.

A Proof Of Ghost Freedom In de Rham-Gabadadze-Tolley Massive Gravity

On Riemann Hypothesis

A proof of the Riemann Hypothesis:

The Riemann Hypothesis is Unprovable:

First law for BH binaries

Alexandre Le Tiec, Luc Blanchet, Bernard F. Whiting

First laws of black hole mechanics, or thermodynamics, come in a variety of different forms. In this paper, from a purely post-Newtonian (PN) analysis, we obtain a first law for binary systems of point masses moving along an exactly circular orbit. Our calculation is valid through 3PN order and includes, in addition, the contributions of logarithmic terms at 4PN and 5PN orders. This first law of binary point-particle mechanics is then derived from first principles in general relativity, and analogies are drawn with the single and binary black hole cases. Some consequences of the first law are explored for PN spacetimes. As one such consequence, a simple relation between the PN binding energy of the binary system and Detweiler's redshift observable is established. Through it, we are able to determine with high precision the numerical values of some previously unknown high order PN coefficients in the circular-orbit binding energy. Finally, we propose new gauge invariant notions for the energy and angular momentum of a particle in a binary system.

The quantum state cannot be interpreted statistically

Quantum states are the key mathematical objects in quantum theory. It is therefore surprising that physicists have been unable to agree on what a quantum state represents. There are at least two opposing schools of thought, each almost as old as quantum theory itself. One is that a pure state is a physical property of system, much like position and momentum in classical mechanics. Another is that even a pure state has only a statistical significance, akin to a probability distribution in statistical mechanics. Here we show that, given only very mild assumptions, the statistical interpretation of the quantum state is inconsistent with the predictions of quantum theory. This result holds even in the presence of small amounts of experimental noise, and is therefore amenable to experimental test using present or near-future technology. If the predictions of quantum theory are confirmed, such a test would show that distinct quantum states must correspond to physically distinct states of reality.

EMRI resonances

Jonathan Gair,1 Nicola ́s Yunes,2, 3 and Carl M. Bender4

An expected source of gravitational waves for future detectors in space are the inspirals of small compact objects into much more massive black holes. . On short timescales the orbit of the small object is approximately geodesic. Over the course of an inspiral, a typical system will pass through resonances where two of these frequencies become commensurate. The effect of the resonance will be to alter significantly the rate of inspiral for the duration of the resonance.

Update on superluminal neutrinos from OPERA

An update on OPERA's observation of superluminal neutrinos has been posted on the hep-ex arxiv:

See some discussion on this here.

Astrology beliefs among undergraduate students

This paper did not appear on astro-ph, nonetheless i'd like to discuss it.

It is about the perception of astrology and other unscientific views.

2011 Nobel Prize in Physics

Awarded to Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess.

Measurement of the neutrino velocity with the OPERA detector in the CNGS beam


The OPERA CollaboratonT. AdamN. AgafonovaA. AleksandrovO. AltinokP. Alvarez SanchezS. AokiA. ArigaT. ArigaD. AutieroA. BadertscherA. Ben DhahbiA. BertolinC. BozzaT. BrugiéreF. BrunetG. BrunettiS. BuontempoF. CavannaA. CazesL. ChaussardM. ChernyavskiyV. ChiarellaA. ChukanovG. ColosimoM. CrespiN. D'AmbrosiosY. DéclaisP. del Amo SanchezG. De LellisM. De SerioF. Di CapuaF. CavannaA. Di CrescenzoD. Di FerdinandoN. Di MarcoS. DmitrievskyM. DracosD. DuchesneauS. DusiniJ. EbertI. EftimiopolousO. EgorovA. EreditatoL.S. EspositoJ. FavierT. FerberR.A. FiniT. FukudaA. GarfagniniG. GiacomelliC. GirerdM. GiorginiM. GiovannozziJ. GoldbergaC. GöllnitzL. GoncharovaY. Gornushkinet al. (117 additional authors not shown)

(Submitted on 22 Sep 2011)

The OPERA neutrino experiment at the underground Gran Sasso Laboratory has measured the velocity of neutrinos from the CERN CNGS beam over a baseline of about 730 km with much higher accuracy than previous studies conducted with accelerator neutrinos. The measurement is based on high-statistics data taken by OPERA in the years 2009, 2010 and 2011. Dedicated upgrades of the CNGS timing system and of the OPERA detector, as well as a high precision geodesy campaign for the measurement of the neutrino baseline, allowed reaching comparable systematic and statistical accuracies. An early arrival time of CNGS muon neutrinos with respect to the one computed assuming the speed of light in vacuum of (60.7 \pm 6.9 (stat.) \pm 7.4 (sys.)) ns was measured. This anomaly corresponds to a relative difference of the muon neutrino velocity with respect to the speed of light (v-c)/c = (2.48 \pm 0.28 (stat.) \pm 0.30 (sys.)) \times 10-5.


Hybrid method for GW merger signals

Nichols and Chen, Caltech

We adapt a method of matching post-Newtonian and black-hole-perturbation theories on a timelike surface (which proved useful for understanding head-on black-hole-binary collisions) to treat equal-mass, inspiralling black-hole binaries. We first introduce a radiation-reaction potential into this method, and we show that it leads to a self-consistent set of equations that describe the simultaneous evolution of the waveform and of the timelike matching surface. This allows us to produce a full inspiral-merger-ringdown waveform of the l=2, m=2,-2 modes of the gravitational waveform of an equal-mass black-hole-binary inspiral. These modes match those of numerical-relativity simulations well in phase, though less well in amplitude for the inspiral. As a second application of this method, we study a merger of black holes with spins antialigned in the orbital plane (the "superkick" configuration). During the ringdown of the superkick, the phases of the mass- and current-quadrupole radiation become locked together, because they evolve at the same quasinormal mode frequencies. We argue that this locking begins during merger, and we show that if the spins of the black holes evolve via geodetic precession in the perturbed black-hole spacetime of our model, then the spins precess at the orbital frequency during merger. In turn, this gives rise to the correct behavior of the radiation, and produces a kick similar to that observed in numerical simulations.

Type Ia SN Discovered in M101

ATel #3581: Young Type Ia Supernova PTF11kly in M101

Higher-order self-force calculations for scalar fields via effective field theory

The motion of a small compact (SCO) object in a background spacetime is investigated further in the context of a class of model nonlinear scalar field theories that have a perturbative structure analogous to the General Relativistic description of extreme mass ratio inspirals (EMRIs). We derive regular expressions for the scalar perturbations generated by the motion of the compact object that are valid through third order in ε, the size of the SCO to the background curvature length scale. Our results for the field perturbations are compared to those calculated through second order in ε by Rosenthal in [1] and found to agree. However, our procedure for regularizing the scalar perturbations is considerably simpler. Following the Detweiler-Whiting scheme, we use our results for the regular expressions for the field and derive the regular self-force corrections through third order. We find agreement with our previous derivation based on a variational principle of an effective action for the worldline associated with the SCO thereby demonstrating the internal consistency of our formalism. This also explicitly demonstrates that the Detweiler-Whiting decomposition of Green’s functions is a valid and practical method of self force computation at higher orders in perturbation theory and, more generally, at all orders in perturbation theory, as we show in an appendix. Finally, we identify a central quantity, which we call a master source, from which all other physically relevant quantities are derivable. Specifically, knowing the master source through some order in ε allows one to construct the waveform measured by an observer, the regular part of the field and its derivative on the worldline, the regular part of the self force, and various orbital quantities such as shifts of the innermost stable circular orbit, etc., when restricting to conservative dynamics. The existence of a master source together with the regularization methods implemented in this series should be indispensable for derivations of higher-order gravitational self force corrections in the future.

A quasi-radial stability criterion for rotating relativistic stars


The stability properties of relativistic stars against gravitational collapse to black hole is a classical problem in general relativity. A sufficient criterion for secular instability was established by Friedman, Ipser and Sorkin (1988), who proved that a sequence of uniformly rotating barotropic stars is secularly unstable on one side of a turning point and then argued that a stronger result should hold: that the sequence should be stable on the opposite side, with the turning point marking the onset of secular instability. We show here that this expectation is not met. By computing in full general relativity the $F$-mode frequency for a large number of rotating stars, we show that the neutral-stability point, i.e., where the frequency becomes zero, differs from the turning point for rotating stars. Using numerical simulations we validate that the new criterion can be used to assess the dynamical stability of relativistic rotating stars.

Dust destruction in the ISM: a re-evaluation of dust lifetimes

A. P. Jones and J. A. Nuth III


Context. There is a long-standing conundrum in interstellar dust studies relating to the discrepancy between the time-scales for dust
formation from evolved stars and the apparently more rapid destruction in supernova-generated shock waves.
Aims. We re-examine some of the key issues relating to dust evolution and processing in the interstellar medium.
Methods. We use recent and new constraints from observations, experiments, modelling and theory to re-evaluate dust formation in
the interstellar medium (ISM).
Results. We find that the discrepancy between the dust formation and destruction time-scales may not be as significant as has previ-
ously been assumed because of the very large uncertainties involved.
Conclusions. The derived silicate dust lifetime could be compatible with its injection time-scale, given the inherent uncertainties in
the dust lifetime calculation. The apparent need to re-form significant quantities of silicate dust in the tenuous interstellar medium
may therefore not be a strong requirement. Carbonaceous matter, on the other hand, appears to be rapidly recycled in the ISM and,
in contrast to silicates, there are viable mechanisms for its re-formation in the ISM.

Fix the PhD

This week's issue of Nature has a special on the future of the PhD. In a series of articles the academic pyramid (Ph.D. student/post-doc/permanent staff) is being discussed, in particular the perceived overproduction of PhDs, induced by funding systems around the world. The editorial provides a good summary of various viewpoints:

NASA: wiping the slate clean

IXO and LISA are dead and disbanded as NASA missions.
We are looking at a very thin pipeline and few new missions for a while, unless there is drastic new direction from above and strong guidance on funding.

Modelling the reflective thermal contribution to the acceleration of the Pioneer spacecraft

F. Francisco, O. Bertolami, P. J. S. Gil, J. Páramos

(Submitted on 27 Mar 2011)

Comments: 11 pages, 7 figures, 3 tables

Subjects: Space Physics (; Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)


We present an improved method to compute the radiative momentum transfer in the Pioneer 10 & 11 spacecraft that takes into account both diffusive and specular reflection. The method allows for more reliable results regarding the thermal acceleration of the deep-space probes, confirming previous findings. A parametric analysis is performed in order to set an upper and lower-bound for the thermal acceleration and its evolution with time.

Angular momentum of light from black holes

Formal navier-stokes/gravity duality?

We show by explicit construction that for every solution of the incompressible Navier-Stokes equation in $p+1$ dimensions, there is a uniquely associated "dual" solution of the vacuum Einstein equations in $p+2$ dimensions. The dual geometry has an intrinsically flat timelike boundary segment $\Sigma_c$ whose extrinsic curvature is given by the stress tensor of the Navier-Stokes fluid. We consider a "near-horizon" limit in which $\Sigma_c$ becomes highly accelerated. The near-horizon expansion in gravity is shown to be mathematically equivalent to the hydrodynamic expansion in fluid dynamics, and the Einstein equation reduces to the incompressible Navier-Stokes equation. For $p=2$, we show that the full dual geometry is algebraically special Petrov type II. The construction is a mathematically precise realization of suggestions of a holographic duality relating fluids and horizons which began with the membrane paradigm in the 70's and resurfaced recently in studies of the AdS/CFT correspondence.

A candidate redshift z ≈ 10 galaxy and rapid changes in that population at an age of 500 Myr

Searches for very-high-redshift galaxies over the past decade have yielded a large sample of more than 6,000 galaxies existing just 900–2,000 million years (Myr) after the Big Bang (redshifts 6 > z > 3; ref. 1). The Hubble Ultra Deep Field (HUDF09) data have yielded the first reliable detections of z ≈ 8 galaxies that, together with reports of a γ-ray burst at z ≈ 8.2 (refs 10, 11), constitute the earliest objects reliably reported to date. Observations of z ≈ 7–8 galaxies suggest substantial star formation at z > 9–10 (refs 12, 13). Here we use the full two-year HUDF09 data to conduct an ultra-deep search for z ≈ 10 galaxies in the heart of the reionization epoch, only 500 Myr after the Big Bang. Not only do we find one possible z ≈ 10 galaxy candidate, but we show that, regardless of source detections, the star formation rate density is much smaller (~10%) at this time than it is just ~200 Myr later at z ≈ 8. This demonstrates how rapid galaxy build-up was at z ≈ 10, as galaxies increased in both luminosity density and volume density from z ≈ 10 to z ≈ 8. The 100–200 Myr before z ≈ 10 is clearly a crucial phase in the assembly of the earliest galaxies.

Reduced basis for GW templates

We introduce a reduced basis approach as a new paradigm for modeling, representing and searching for gravitational waves. We construct waveform catalogs for non-spinning compact binary coalescences, and we find that for accuracies of $99\%$ and $99.999\%$ the method generates a factor of about $10-10^5$ fewer templates than standard placement methods. The continuum of gravitational waves can be represented by a finite and comparatively compact basis. The method is robust under variations in the noise of detectors, implying that only a single catalog needs to be generated.

Phenomenological gravitational waveforms from spinning coalescing binaries