LIGO's second detection

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

Plenary Session: The Elephant in the Room: Effects of Distant, Massive Companions on Planetary System Architectures (by Leonardo dos Santos)

The first session on Wednesday at 228th AAS Meeting was the Newton Lacy Pierce Prize Lecture by Heather Knutson (California Institute of Technology). This talk featured a broad range of research efforts on exoplanets, with the main focus on how we study the composition of their atmospheres, and how multi-body interactions carve the structure of the planetary systems we observe.

One of her first points is the well-known idea that the Solar System is an oddball, compared to the exoplanet systems we have found so far: most of these systems contain hot Jupiters and mini-Neptunes at very close-in orbits around their host stars. Moreover, even when studying their transmission spectra, it is difficult to know the exact composition of their atmospheres.

The main proposal on how these systems formed is the migration scenario. In order to validate this idea, Dr. Knutson and her group — The Friends of Hot Jupiters — study systems with close-in gas giants and their frequency of binary companions, which are supposed to be the main culprits causing gas-giant migration. They found that approximately half of the observed systems have long-distance companions, providing strong validation of the migration scenario. Moreover, Dr. Knutson speculates that wide binaries have more massive disks, which in turn produce more gas giants, populating our surveys with such planets.

Dr. Knutson shows that ~50% of hot Jupiters have long distance companions.

Dr. Knutson shows that ~50% of hot Jupiters have long distance companions.

Press Conference: Latest News from the LIGO Scientific Collaboration (by Michael Zevin)

On December 26th 2015, LIGO detected its second full-fledged gravitational wave event, dubbed GW151226 (the numbers signify the date it was detected). This detection along with the full results of LIGO’s first observing run were announced by Gabriela González, David Reitze, and Fulvio Ricci in the morning press conference. The masses of the two black holes are smaller than those of the first confirmed event (GW150914) – about 8 & 14 solar masses for GW151226 compared to 29 & 36 solar masses for GW150914. Though less visible by eye in the data, sophisticated search algorithms that match theoretically-produced templates of the gravitational waveform were able to extract it from the data and build up enough statistical confidence to declare it as a detection. The system was estimated to have merged at a distance of 1.4 billion light-years, and, due to its lower mass, stayed in LIGO’s detection band for a full second (5 times longer than the more massive GW150914).

Time-frequency plot of the second confirmed gravitational wave event - GW151226. Light colors represent higher energy.

Time-frequency plot of the second confirmed gravitational wave event – GW151226. Light colors represent higher energy.

This discovery further solidifies this nascent field into astronomy, and has given astronomers a new sense to explore the Universe. The next observing run of LIGO will commence later in 2016 and will be more sensitive due to system upgrade, increasing the rate at which LIGO should detect these types of astrophysical events. In addition, more detectors will be joining the network of gravitational wave observatories over the next few years, which will further constrain the location at which these events occur in the cosmos and increase the likelihood of detecting an electromagnetic counterpart to a gravitational wave event. More great discoveries to come!

Our zoo of stellar-mass black holes, including the 2 confirmed LIGO event, the 1 LIGO candidate, and indirect evidence from X-ray binaries.

Our zoo of stellar-mass black holes, including the 2 confirmed LIGO event, the 1 LIGO candidate, and indirect evidence from X-ray binaries.

Star Formation in a Range of Environments (by Benny Tsang)

David Cook began our morning star formation session with his work on the connection between the slopes of luminosity functions for star-forming regions and the host-galaxy properties. A moderate-strong trend was found: galaxies with higher star formation rate surface densities (the star formation rate per area projected on the sky) tend to have flatter luminosity functions. It was interpreted as the result of increased star formation efficiencies in high-density environments, which led to a large number of bright regions. Next, Daniel Carson presented his dissertation work on the observations of nuclear star clusters in disk galaxies. Radially-varying stellar populations were found. Stellar population modeling also revealed the star formation histories and stellar masses of the clusters. The stellar mass surface density of IC342 was measured to lie above the theoretical maximum set by stellar feedback.

Kaveh Vasei took us on his journey estimating the escape fraction of Lyman continuum photons from galaxies. He argued that the commonly used indirect methods in determining the escape fraction should only be interpreted as upper limits, and showed us the highest-resolution image of Lyman continuum leakers so far. David Guszejnov then led the first theoretical talk on modeling star formation using semi-analytical models – an approach between full-blown numerical simulations and pen-and-paper calculations. The advantage of such an approach is that you could explore different star formation models (with or without feedback) very quickly. The semi-analytical models with feedback reproduced observables such as the slope and turnover of the initial mass function well, and this technique can also further the understanding of binary-star formation.

Philip Hopkins then continued the theoretical discussion and showed that enough ionizing photons for cosmic reionization could be obtained if we consider binary stars. The idea is that material transfer within binary systems could extend the lifetimes of massive stars, thereby allowing them to produce enough ionizing photons before they die. Veronica Allen closed the session by sharing with us her work on characterizing the chemistry in the massive star-forming region G35.20-0.74N. An asymmetric distribution of nitrogen-bearing species was found, which could be due to disk fragmentation on unresolved scales and the formation of multiple sources with different ages.

Plenary Session: Observation of Gravitational Waves (by Susanna Kohler)

Gabriela González, spokesperson for the LIGO Scientific collaboration.

Gabriela González, spokesperson for the LIGO Scientific collaboration.

Following this morning’s exciting press conference, Gabriela González, spokesperson for the LIGO Scientific collaboration, gave the Kavli Foundation Plenary Lectureship. Though the Kavli lecture usually opens the AAS meeting, it was moved this week to accommodate the schedule for LIGO’s big announcement today!

González opened the plenary by digging a little further into the physics of LIGO detections. She described how the detectors work, pointing out that they’re designed to detect a strain of 1 part in 1021. This is roughly the same as measuring if the Earth-Sun distance changed by the size of a single atom!

Our ability to localize gravitational-wave detections currently relies on the timing of the observations: noting the difference in time between when the signal passes the LIGO Livingston and LIGO Hanford detectors (on the scale of 10 ms) can give us a broad sense of where in the sky the signal came from. Our ability to localize will significantly improve when future detectors like Virgo (Europe), LIGO-India, and KAGRA (Japan) come online within the next decade.

González spoke more about the detections that LIGO has made thus far. There were actually three significant gravitational-wave triggers in the first science run; the third has an 85% probability of being astrophysical, compared to the nearly 100% probability of the two official detections. The fact that there have been so many detections already — despite the fact that LIGO is only at 40% of its design sensitivity — suggest that we can expect many more to come!

As a final note, González pointed out that detections by ground-based gravitational-wave interferometers are only the start of gravitational-wave astronomy. Future observatories and missions (like eLISA, and improved-sensitivity pulsar timing arrays) will expand the search for gravitational waves to different frequency ranges.

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

The Limits of Scientific Cosmology: Setting the Stage: Accepted Facts, and Testing Limitations in Theory and Data (by Gourav Khullar)

With a stellar lineup of speakers to talk about current and future prospects of cosmology and its limits (or lack thereof), the first session kicked off with talks by Risa Wechsler, Joseph Silk, and Sean Carroll (his talk on Multiverses is described below, by Nathan Sanders). Risa set the stage with an elaborate description of the current accepted facts in the era of precision cosmology including the standard model of concordance cosmology, described by seven parameters and an accepted Lambda-CDM paradigm (with a cosmological constant and cold dark matter). The talk stressed on the fact that all these parameters are understood to a percent order precision, which is a remarkable deviation from the time in 1990s when according to Risa, “Alan Guth never thought that any of these numbers could be measured precisely!”

Risa Wechsler describing our current constraints on what Dark Matter could constitute.

Risa Wechsler describing our current constraints on what Dark Matter could constitute.

Joseph Silk discussing limits on cosmological parameters.

Joseph Silk discussing limits on cosmological parameters.

The CMB measurements, Big Bang Nucleosynthesis estimates and galaxy clustering statistics all contribute to locking down the description of our universe. She emphasized on the tensions between different probes to measure expansion rate H0 of the universe, and small scale predictions of cold dark matter simulations, but she is hopeful that these shall be resolved eventually. Joe Silk followed this up with his interpretation of trying to understand our place in the universe and placing limits on different parameters and scales that we measure, ranging from star masses to dark energy scale estimates.

By invoking the anthropic principle, Silk pointed out that perhaps multiverses could offer a potential solution to certain causes of concern in our current models. The future looked good, and according to Silk, a better characterization of non-gaussianities using powerful simulations and precise CMB measurements is the way to go.

The Limits of Scientific Cosmology: Normal Science in a Multiverse (by Nathan Sanders)

Slotted into the “contrarian” slot of this special session on the limits of cosmology, Sean Carroll (Caltech) made a powerful argument for the normalcy of the multiverse prediction of inflationary and other theories of cosmology. While other scientists, including earlier speakers in the session, suggested that the intense difficulty of collecting data directly testing the multiverse prediction disqualifies it as a “scientific” theory, Carroll argued that this is no different from the reality of the scientific process applied generally. He combats the absolutist interpretation of Karl Popper’s writing on demarcation, which implies that only imminently-falsifiable theories qualify as “scientific.” Instead, he points us to abduction as the fundamental motive of science, the idea that we seek to move towards the model that best explains the available evidence, closely related to Bayes’ theorem. He acknowledged that we may never collect enough evidence for our credence in the multiverse to converge to one, and yet it may definitely be true.  While he puts his own credence in the multiverse at “about 50%,” Carroll concludes that we should not reject the possibility of the multiverse out of hand solely on the basis of philosophical arguments.

Surprisingly, Carroll also comments that evidence can include both data and theory, specifically new interpretations of old ideas and new predictions. For example, Einstein did not make new observations of the precession of Mercury to lend credence (in the scientific sense) to his then-new theory of general relativity.  Instead, he applied his theory for the first time to the orbit of Mercury and demonstrated that it explains existing facts. In the same way, we may add or remove credence from the multiverse theory even without newly collected measurements on directly testable predictions.

Plenary Session: APOGEE: The New View of the Milky Way (by Nathan Sanders)

Jo Bovy (Toronto) spoke about a bevy of recent discoveries by the APOGEE team, which has collected half a million spectra of red giant stars throughout the Milky Way disk.  Bovy emphasized APOGEE’s unprecedented scope, covering close to half of the Milky Way disk and ranging ~10 kpc in radius, rather than the tiny neighborhood around the sun that most historical stellar surveys have probed.  Overcoming the challenges of galactic extinction, the APOGEE team has made the most precise measurement of the circular rotation velocity of the MIlky Way disk, v_c = 218 +- 6 km/s, and produced remarkable results on the chemical evolution history of the Galaxy.  In particular, they have shown that the star formation and chemical evolution history of the Galaxy seems to be remarkably constant throughout the disk. However, the radial migration of stars, which follows a non-circular orbit across the Milky Way’s spiral structure, causes mixing that makes the distribution of stellar parameters look uneven.  Bovy also emphasized the importance of open science, sharing data and code related to their work.  Like all SDSS data, the APOGEE spectra have been released publicly, and all their software pipelines and stellar models have also been made public.  Coming next is an APOGEE-2 survey of the Southern sky, a copy of the instrument to be installed at the DuPont telescope in Chile.

Press Conference: Dark Skies, Aliens, and the Multiverse (by Chris Faesi)

Tuesday afternoon brought another press conference to the AAS 228th meeting, this one taking us beyond the benign realms of planets, stars, and galaxies to Dark Skies, Aliens, and the Multiverse.

Earth at night

A view of Earth’s artificial light. [NASA Earth Observatory]

First, Eric Craine of STEM Lab, Inc. unveiled a new tool, the LANI (Light at Night Index), for measuring light pollution across a comprehensive sample of US communities: Using satellite data, LANI provides an estimate of the lighting efficiency in each US community having more than 500 people (comprising 19000+ cities and towns in total). The score incorporates the measured radiance (brightness), taking into account the number of people, the number of housing units, and the community area, and is then normalized to be between 1 and 100.  LANI can be used to assess where additional efforts are needed to improve energy efficiency and reduce light pollution, as well as to track changes in infrastructure and population over time. Read more about the LANI here.

Next, Evan Solomonides, an undergraduate student at Cornell University, presented a probabilistic analysis of the Fermi Paradox, the famous statement that asserts that if life is common in the Universe (as many believe), we should have detected it by now. The basic takeaway from his work is that while we’ve been sending powerful radio transmissions into space for the last 80 years, the volume of space reached by these transmissions is incredibly insignificant (perhaps 10 parts per million) compared to the size of our galaxy. If similar civilizations to ours have cropped up across the Milky Way and had even significantly longer timescales over which to send out signals, it is actually not surprising that we haven’t seen them yet, simply by virtue of the vastness of space. Solomonides predicts that it will be about 1500 years before it is probabilistically favorable to detect extraterrestrial civilizations, based on these assumptions.

Finally, cosmologist and science communicator extraordinaire Sean Carroll zoomed the focus out beyond the galaxy, beyond the observable universe, to the basic question of what it even means to do science in a multiverse. Carroll argued that even if a scientific theory is unable to be directly tested, it should not be automatically discarded as impossible or irrelevant. One cannot definitively prove that beyond the observable universe lie regions of space that have vastly different physical properties or cosmologies – in other words, the existence of a multiverse – and so this possibility should at least be philosophically considered by scientists, and the potential influences that the multiverse would have on the observable universe should be looked for.

Classification and Properties of Variables, Binaries and White Dwarfs and Stellar Evolution (by Ashley Villar)

In this era of big data, our ability to classify the plethora of celestial objects we detect is essential to our science. Gideon Bass began this session by discussing his work in using machine learning to classify Kepler variable stars. Bass ties together many machine learning algorithms to create a “Frankenstein” method to maximize accuracy. At higher energies, Saeqa Vrtilek discussed the use of color-color-intensity diagrams in X-ray wavelengths to classify objects such as cataclysmic variables, black holes and neutron stars.

Eclipse of Epsilon Aurigae.

Eclipse of Epsilon Aurigae by dusty disk.

Imre Bartos moved away from classification to discuss potential electromagnetic counterparts to black hole-black hole mergers. Specifically, stellar mass black holes near the center of galaxies are more likely to collide within only a million years due to friction. Richard Ignace discussed the polarization of Epsilon Aurigae. This odd binary undergoes eclipses about once every quarter of a century, when a dusty disk passes in from of the primary star, as shown above.

Tomomi Otani explained how we can look for planets and other companions around post main sequence stars, or stars which have finished burning hydrogen. One of the six targets (named PG-1219+534) from her survey in fact has a planet which has survived its host star’s drastic expansion as it reached the red giant branch. Finally, Paula Szkody explained the exotic light curves of cataclysmic variables found with K2. These detailed observations allow us to understand previously unseen bumps and wiggles in the light curves due to the complex physics driving these systems.

The Limits of Scientific Cosmology: Historical and Cosmological Context (by Gourav Koullar)

Karl Popper was everywhere today, being invoked by both Matt Stanley and Sean Carroll.

Karl Popper was everywhere today, being invoked by both Matt Stanley and Sean Carroll.

The second session of this forum constituted a series of talks aimed at setting the premise for our current understanding of the universe, and the very story of how cosmology came to be a science. Matt Stanley gave us an extraordinary tour of the last 150 years of scientific tendencies to create models of the universe. John Tyndall, James Clark Maxwell, Ernst Mach all joined the party, as we moved towards the Friedman-Lemaitre-Robertson-Walker model and Einstein’s tweaks to his field equations in General Relativity. Stanley gave due credit to the Steady State Cosmology ‘movement’, since it was using Popperian falsifiability that Hermann Bondi and Fred Hoyle established the rules of how a theory of the universe should look like. Even today, as we wage an internal battle between ‘Adaptive Optimism’ and ’Pessimistic Induction’ as scientists, our willingness understand the cosmos stays strong. 

Richard Dawid followed this up with a new philosophical theory of science, putting an emphasis on non-empirical confirmation of theories, and tracking evolution of credence (e.g. in a Bayesian manner) instead of definitive ‘true’ or ‘false’ answers to fundamental questions. Virginia Trimble brought the afternoon discussion to a conclusion by discussing a very unique empirical observation: whenever a community has come at a juncture where the choice has been between one or many, finite or ‘infinite’ (in a non-mathematical sense!), the latter has always won the debate. Whether we talk about a small Ptolemaic geocentric universe or a larger-than-life Copernican heliocentric solar system, the Milky way being the only galaxy vs. us being one of many, or a static versus an accelerating universe, the latter has been victorious. Hence Trimble asks, then who are we to stop at a universe, with existing ideas of a multiverse!

Stay tuned for tomorrow’s parts III and IV of The Limits of Scientific Cosmology!

Plenary Session: Things That Go Bump in the Night: The Transient Radio Sky (by Susanna Kohler)

This afternoon plenary was given by Dale Frail of the National Radio Astronomy Observatory, who injected some pop culture into our day by introducing radio transients as some of the night’s terrors that Game of Thrones warned us about.

Transient sources are those that change, often rapidly, while we observe them. Radio transients are an incredibly broad category, spanning sources that can vary on fraction-of-a-second timescales (like pulsars) to year-long timescales (like jets from active galactic nuclei).

In general, Frail emphasized, the radio sky is quiet; radio transients are actually quite rare. But the list of potential radio transients, while including many known sources, also pushes into more speculative territory. Interesting examples include the mysterious Fast Radio Bursts (FRBs) discussed in yesterday’s plenary by Maura McLaughlin, and electromagnetic counterparts to gravitational waves.
Frail gave an overview of what we currently know about the radio transients that we’ve observed — including where we find them, what energies they span within the radio band, and what timescales they vary on.
He also discussed the different strategies used to learn more about the transient radio sky: we’re generally faced with the choice to either “be a cartographer” by using all-sky surveys to search for new transients, or “be a buccaneer” by strategically following up on survey leads to localize and identify transient sources.

Frail argued that the way forward is to combine these strategies: use all-sky radio surveys coupled with rapid multi-wavelength follow-up. This combines the serendipitous element of surveys — the ability to find things we weren’t necessarily searching for, such as the first pulsar signal ever detected — with the higher-precision tools needed to identify what we’re looking at.

Plenary Session: MAVEN Observations of Atmospheric Loss at Mars (by Meredith Rawls)

One of the best ways to learn about exoplanets is by carefully studying planets much closer to home. Shannon Curry emphasized this throughout her presentation about Mars’ atmosphere, which was motivated by the fact that Mars used to be a warmer, wetter planet. The Mars Atmosphere and Volatile Evolution orbiter (MAVEN) arrived at Mars in September 2014 and has been collecting many kinds of data about the Martian atmosphere ever since.

Several different processes are responsible for Mars losing parts of its atmosphere to space. Because Mars is a relatively small planet, it has had a difficult time holding onto its atmosphere over the history of the Solar System. Neutral particles, ionized particles, and even water vapor all find unique ways to escape the grip of Mars’ gravity. In addition, the variable effects of the Solar wind and other space weather affect what kind of material is lost.

Beyond the detailed physics and chemistry illustrated above, the differences in Mars’ atmosphere as a function of the Sun’s behavior are a challenge to observe because the Sun is experiencing a quiet solar maximum with relatively few coronal mass ejections. Thanks to MAVEN, we have the first opportunity to measure these processes up close. Mars serves as an excellent analog for exoplanet hydrogen loss and can tell us whether similarly-sized planets are likely to have the same fate.

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

Plenary Session: The Galaxy Zoo (by Benny Tsang)
Galaxy Zoo was so hot that the servers hosting the galaxy images got melted down soon after being launched.

Galaxy Zoo was so hot that the servers hosting the galaxy images got melted down soon after being launched.

Kevin Schawinski from ETH Zurich took us on a tour of his wonderful Galaxy Zoo. It is a huge zoo with about a quarter million zookeepers, citizen astronomers who collaboratively classify galaxies by their looks in an attempt to understand galaxy evolution. The big question that is being answered is: how do blue, actively star-forming galaxies evolve into red, quiescent (non-star-forming) galaxies? The Zoo helped reveal that blue galaxies turn into red galaxies via two possible paths: 1) galaxies might run out of their gas supply and shut off star formation slowly, or 2) galaxies could merge with one another and turn off star formation by destroying the gas reservoir rapidly!

The Galaxy Zoo project also led to the discoveries of:

  • “Green Peas”: the “living fossils” of galaxy evolution. These are compact, bright, green galaxies that are actively forming stars.
  • Overlapping galaxies: pairs of galaxies that are separated physically but happen to lie on the same line of sight. These provide excellent laboratories for studying dust extinction.
  • “Hanny’s Voorwerp”: an unusual object named after Hanny van Arkel, the discoverer. This is believed to be the first detection of a quasar light echo.

Galaxy Zoo’s idea to get help from citizen scientists was further extended into an award-winning project known as the Zooniverse, which is an online platform for streamlined crowd-sourcing for scientific research that requires human input. As the future of astronomy is going to be extremely data-rich, the Galaxy Zoo project has also explored combining the help from citizen scientists with machine learning to analyze extremely large datasets.

Extrasolar Planets: Atmospheres (by Leonardo dos Santos)
Antonija Oklopčić (Caltech) explains that Raman scattering of light, which works similarly to Rayleigh scattering (the process that makes Earth’s sky blue), can be used in the future to study the atmospheres of exoplanets. Her work is to create model spectra containing these features, from which we can learn about the presence and altitude of atmospheric clouds. Dr. Carl Melis (University of California, San Diego) studies the inner composition of exoplanets by looking at their remnants after they are destroyed by a dying star. His most recent work suggests that there is a differentiated pollution (from the core and the crust of a planet) in the disk orbiting of a white dwarf star. Samuel Grunblatt (University of Hawaii) introduces us to the main subject of his thesis: a hot-Jupiter observed by Kepler’s K2 mission transiting an evolved, red giant star. They used some pretty tricky data analysis in order to filter out the noise intrinsic to this type of star.

Grunblatt shows the K2 transit before and after removal of granulation effects.

Avi Shporer (JPL) asks the question: why are hot Jupiters so large? His research aims to study the correlation between stellar irradiation and planetary radius, and in order to have a more complete picture, they need to detect more gas giants on lower stellar irradiation regions. This idea gave rise to LCOGT K2 Warm Jupiter project, which recently discovered a brown dwarf in a long-period orbit around a Sun-like star. Paul Mason (New Mexico State University) proposes that the Milky Way is evolving to a more habitable galaxy, due to the expansion of the universe, the processing of heavier material inside stars, and the general decrease of ionizing radiation.

Evolution of Galaxies (by Ben Cook)
Tuesday morning’s panel on the lifecycles of galaxies began with a talk by Ben Cook (astrobites author) on how we can infer whether a galaxy experienced large mergers. Cook used the Illustris simulation to study how stars are left in so-called “stellar halos” far outside galaxies after they have large collisions. Yicheng Guo then showed evidence that lower-mass galaxies tend to form their stars in a few large bursts, rather than long, steady formation like in more massive galaxies. Ali Khostavan measured the strengths of particular emission lines, which are found to increase further back in time, telling us that galaxies were forming many more stars early on in the universe than they are now.


Artist's impression of the heart of an active galaxy, known as an Active Galactic Nucleus (AGN). [NASA/Goddard Space Flight Center Conceptual Image Lab]

Artist’s impression of the heart of an active galaxy, known as an Active Galactic Nucleus (AGN). [NASA/Goddard Space Flight Center Conceptual Image Lab]

Irene Shivael presented a new measurement of the relationship between the star-formation rate of a galaxy and the mass of its stars (i.e., its stellar mass). This relation has been measured to have very different values by a large number of different studies! Gene Leung look at the spectra of Active Galactic Nuclei (AGN) and found that many of them are blowing out large blobs of gas into the space around their host galaxies. This process is an important part of how we think galaxies shut off their star formation: the AGN blow the gas far away, so it cannot collapse and form new stars.


Rui Xue studied large glowing halos of Lyman-alpha emission that are seen around high-redshift galaxies. This emission is lighting up the gas around each galaxy and can be used to measure the “circum-galactic medium,” the stuff around galaxies extremely far away. SungWon Kwak ran new simulations to study how small (dwarf) galaxies can form central bars or spiral arms when they fall into clusters or collide with other galaxies. Dusan Keres closed out the session by talking about a new, very powerful simulation called FIRE, which uses very complicated star-formation models and tries to model galaxies with as high resolution as possible.


Small Telescope Research Communities of Practice (by Ashley Villar)

Although astronomers are building larger and larger telescopes to study the farthest reaches of space, recent advances in camera technology are opening the gates for backyard enthusiasts to explore cutting-edge science. Dave Rowe opened the session with a short talk on a technique called speckle interferometry. In short, this technique takes many quick (short exposure) images and averages them using the Fourier power spectrum of the images. This technique lets you separate stars a half arcsecond apart on the sky, or about 1/120th the size of the moon, for a few hundred dollars! Next, Dominic Ludovici explained how his research is bridging the gap between professional and ameateur spectroscopy by utilizing instruments called collimated grisms. Using custom 3D-printed parts, Ludovici is able to take high-quality spectra of everything from Wolf-Rayet stars to quasars for only a few hundred dollars. These tools allow Ludovici to bring science into his college classrooms at the University of Iowa through a series of hands-on observing labs. Virginia Trimble wrapped up the session with some thoughts on communities of practice and collaborations. She underscored the importance of creating an open and welcoming environment for incoming members of any collaboration, and she emphasized that we should build communities of inclusion.

Press Conference: Shaking Hands and Eruptive Variables (by Meredith Rawls)
Tuesday morning’s press conference highlighted two new papers. First, Brandon Carroll from Caltech and Brett McGuire from NRAO presented the first detection of a chiral molecule, propylene oxide, outside our Solar System. Chirality, or “handedness,” is a special property of some molecules that are found in one of two mirror-image versions. Chiral pairs generally have the same properties but different kinds of physical interactions. Biology has a tendency to prefer sugars and proteins that are one chirality only, but it is unknown whether this is a universal preference or a quirk of Earth-based life. Carroll and McGuire’s new detection in a star-forming cloud of material near the center of the Milky Way does not distinguish whether the propylene oxide is left- or right-handed, but it does show that the cosmos is capable of producing complex molecules that are essential to biology. In the future, they hope to use polarized light to directly measure chirality.

Next, Joel Green from STScI presented how a young star surrounded by a bright protoplanetary disk, FU Orionis, has changed since a bright outburst in 1936. Since then, it has consumed some 80 Jupiter’s worth of material! By comparing observations of the disk’s brightness taken twelve years apart, Green showed that the hottest inner regions of the disk have faded significantly while the cooler regions farther out have not. In other words, the star has consumed the hot parts of the disk closest to it and altered the chemical composition in the disk that remains. This is likely what our own Sun experienced as a young star, and has implications for planet formation because the chemical composition of the disk affects what materials are available for forming planets. Green hopes that future observations with the Webb telescope will complement existing Spitzer and SOFIA data.

Mt Etna

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

Plenary Session: From Space Archeology to Serving the World Today: A 20-year Journey from the Jungles of Guatemala to a Network of Satellite Remote Sensing Facilities Around the World (by Michael Zevin)

In the conference’s second plenary session, NASA’s Daniel Irwin turned the eyes of the conference back to Earth by highlighting the huge impact that NASA missions play in protecting and developing our own planet.

Irwin came to be involved in NASA through his work mapping Guatemalan jungles, where he would spend 22 days at a time exploring the treacherous jungles on foot armed with a 1st generation GPS, a compass, and a machete. A colleague introduced Irwin to the satellite imagery that he was exploring, demonstrating how these images are a strong complement to field work. The sharing of this satellite data with nearby villages helped to show the encroachment of agriculture and the necessity of connecting space to the village. Satellite imagery also played a role in archeological endeavors, uncovering dozens of Mayan cities that have been buried for over a millennia by vegetation, and it provided evidence that the fall of the Mayan civilization may have been due to massive deforestation that led to drought.


Glacial retreat in Chile imaged by ISERV.

Irwin displayed the constellation of NASA’s Earth-monitoring satellites that have played an integral role in conserving our planet and alerting the world of natural disasters. He also showed images from the The ISS / SERVIR Environmental Research and Visualization System Completed Operations (ISERV, which Irwin claimed as the instrument acronym that contains the most acronyms). ISERV is a monitoring camera aboard the ISS with 4m resolution of the ground and a 14.5 km by 10 km field of view. This camera is able identify indications of natural disasters to give early-warnings to areas that are potentially threatened, and help analyze disaster aftermath to aid in recoveries. Particularly striking was an image of the retreating glaciers in Chile due to rising global temperatures. 47,000 such images are available to the public at http://earthexplorer.usgs.gov/! The contributions by NASA to the well-being of our planet and civilization are certainly staggering.  

110: Galaxy Clusters (by Ben Cook)

A short session on clusters of galaxies began with X-ray observations by David Buote studying the distribution of mass in a cluster. By measuring the X-ray temperature (using the spectral information) and the intensity of X-rays, Buote derived the amount of gas in each part of the cluster. By assuming hydrostatic equilibrium, this lets you derive the total mass (not just the gas, but also the stars and dark matter!) of the cluster. But it’s unclear so far whether that assumption is valid here. Jack Burns followed this up by discussing the ways we can observe the wreckage when galaxy clusters merge together. These mergers, as Burns puts it, are “the most energetic events since the Big Bang”. When two clusters crash together, their gas is heated to very high temperatures, producing radio emission that is visible as “radio relics”. Reinout Van Weeren used similar observations in the radio to attempt to measure the magnetic fields in a few clusters. Christine Jones looked at the two primary ways of locating clusters — through X-rays and through the Sunyaev–Zel’dovich (SZ) effect in the radio — and concluded that the two methods are different: one method will easily find clusters the other is less likely to see, and vice versa. Angela Berti detected the signal of “galactic conformity” all the way to redshift z=1, an effect that makes galaxies more likely to be found around neighbors that are very similar (in terms of color or shape) than different kinds. Georgiana Ogrean closed the session by showing a merger between two galaxies that is not producing a strong shock front.  

112: Astronomy Education for All: The 2017 Eclipse, Accessibility and NASA (by Meredith Rawls)

This afternoon session kicked off with an advertisement for US-based astronomers’ favorite upcoming event: the 2017 Solar Eclipse. Jay Pasachoff reviewed plans for the August 21, 2017 event and pointed us to resources about choosing the best viewing site and what to expect on the momentous day. We also heard from Denise Smith, Jim Manning, and Daniel McIntosh about various NASA-funded efforts for education and outreach in the classroom and beyond. 

The other two talks from this session focused on the newly-formed AAS Working Group for Accessibility and Disability and what the astronomical community can do to cultivate a more accessible culture. Speakers Jackie Monkiewicz and Lauren Gilbert described how and why inaccessibility is driving people away from the field: by requiring people with disabilities to disclose those disabilities, by maintaining inaccessible buildings and observatories, by acting inappropriately when accommodations are requested, and by not working well in advance of a course or event to anticipate the needs of people with disabilities. To learn more about what you can do to make astronomy accessible, and what efforts are already underway (including right here at AAS 228), see these resources compiled by AstroBetter.

Press Conference: From Molecules to Galaxies (by Leonardo dos Santos)

Chris Arumainayagam (Wellesley College) opens up the press conference with a research being carried on exclusively by undergraduate students. He shows that the formation of complex molecules in space is currently explained by high energy cosmic rays and ultra-violet (UV) photons, but then presents their suggestion that low-energy UV photons may also play a significant role in this process. Additionally, if detected, the presence of the molecule Methoxymethanol could help to prove their hypothesis.

IMG_0262 (1)

Philip Hopkins showing results from press release.

Philip Hopkins (Caltech) shows the work on FIRE, a new galaxy evolution simulation that is pushing the limits of the field, and is very successful in resolving some of its biggest issues, such as the abundance of fluffy galaxies, the cold dark matter hypothesis and the missing satellites problem.

Gregory Walth (University of California, San Diego) and collaborators discovered an unexpected giant luminous star-forming clump on a galaxy at redshift z = 0.61 — which, incidentally, is gravitationally lensed by the galaxy cluster Abell S1063 (z = 0.35). Such clumps are much more common at higher redshifts (z > 2), so this discovery raises questions on how common these objects are in the more local universe, and how they were formed.

Plenary Session: The Brightest Pulses in the Universe (by Michael Zevin)

Fast radio bursts are one of the biggest mysteries in modern astronomy. Attempts to explain their astrophysical origin span from the merging of relativistic objects to pesky aliens (one of these explanations is more accepted than the other). Maura McLaughlin took the audience on a walk through the history of FRBs and how we’ve built our current understanding of these perplexing occurrences.

The story started with the discovery of radio pulsars by Jocelyn Bell in 1967. Due to the periodicity of the radio beam in these newly-discovered objects, the time-series data of the radio sky was almost always Fourier transformed before analysis and burst events were lost in this transformation. McLaughlin believed that FRBs could have been detected as early as the 1970s if this were not the case! The story then jumped ahead to the 2000s, when astronomers (including McLaughlin) took a look back at archival data from as early as 1967 to search for short duration radio transients in our galaxy. In 2007, a Parkes telescope search for such objects in the Small Magellanic Cloud found a very bright radio burst with a strikingly high dispersion measure (which can be correlated to distance) – the first FRB candidate!


McLaughlin admits that even she had her doubts about the astrophysical origin of the Lorimor Burst.

This became known as the Lorimer Burst, and though some skepticism about its astrophysical origin pervaded over the next few years (primarily because to microwave ovens…no joke), the discovery of more FRBs using Parkes, Arecibo, and Green Bank Telescope after 2013 solidified these events as full-fledged astrophysical phenomena! A very recent study (published in 2016) even found that FRBs can repeat, with no obvious periodicity.

 Though there are many theories as to what might cause FRBs, it is clear that there is no viable model that we know of to explain all FRBs. McLaughlin did, however, confirm that hungry aliens operating microwaves is energetically unrealistic.

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

Come visit Astrobites at the AAS booth ... we have swag!

Come visit astrobites at the AAS booth … we have swag!

Things kicked off last night at our undergraduate reception booth. Thanks to all of you who stopped by — we were delighted to hear from undergrads who already know and love the site, educators who want to use it in their classrooms, and students who had not yet been introduced to astrobites and were excited about a new resource!

For the rest of the meeting we will be stationed at the AAS booth in the exhibit hall (booth #211-213), so drop by if you want to learn more (or pick up swag: we’ve got lots of stickers and sunglasses)!

Monday morning was the official start of the meeting. Here are just a few of the talks and workshops astrobiters attended this morning.

Opening Address (by Susanna Kohler)

AAS President Meg Urry kicked off the meeting this morning at 8am with an overview of some of the great endeavors AAS is supporting. We astrobiters had personal motivation to drag ourselves out of bed that early: during this session, Urry announced the new partnership between AAS and astrobites!

Urry touched on some difficult topics in her welcome, including yesterday’s tragedy in Orlando. She reiterated the AAS’s support for the Committee for Sexual-Orientation and Gender Minorities in Astronomy (SGMA). She also reminded meeting attendees about the importance of keeping conference interactions professional, and pointed to the meeting’s anti-harassment policy.

Partnership Announcement (by Michael Zevin)

This morning, the American Astronomical Society announced the new partnership that it will have with Astrobites! We are beyond excited to embark on this new partnership with the Society, which was the culmination of several years of supportive interaction. This new relationship is described further in the press release just issued by AAS.

First plenary: The Ocean World Enceladus (by Chris Faesi)

Enceladus lineup

Enceladus takes its place in the lineup of potential life-bearing solar system bodies.

In the first plenary session of the AAS 228th meeting, Christopher Glein of the University of Toronto took the audience on an exciting tour of the ocean world Enceladus. This small, icy moon of Saturn had been thought rather unremarkable for most of the 2+ centuries since its discovery in 1789, but the Cassini spacecraft’s extended visit over the last decade has revealed it to be a surprisingly dynamic and unique little world. From Cassini’s 23 flybys, we now know that Enceladus is composed of roughly equal parts rock and ice, and, with an albedo of 99%, is the most reflective body in the solar system.

The moon’s surface is not entirely cratered, as are most solar system objects such as our own Moon, but has a southern hemisphere with long fissures that look like tiger stripes on an otherwise smooth surface. Follow-up with the satellite’s highly sensitive instruments revealed that these stripes were heated up to 200 K – much hotter than Enceladus’s typical 75 K surface temperature. There seems to be an energy shortage: the heating expected from Saturn’s tidal influence on the moon is a factor of about ten smaller than what would be required to heat the surface this much. Unraveling this discrepancy is still an area of active study today.

Enceladus also spews powerful jets of salty water and water ice far into space via cryovolcanism, making it the smallest geologically active body in the solar system. Perhaps most intriguingly, this 500 km-diameter moon may be a promising target in the search for extraterrestrial life. The jets are highly alkaline and may contain molecular hydrogen, which links the inorganic and living worlds as a reactant and energy source. Although Cassini’s very fruitful mission will come to a close in 2017 with a death spiral into Saturn, the future is still bright for Enceladus. Glein closed with a preview of the next mission to this special moon: “ELF”, the Enceladus Life Finder, will fly through and analyze Enceladus’s icy plume in unprecedented detail using state-of-the-art instruments and is predicted to fly in 2031.

102: The NASA K2 Mission (by Meredith Rawls)

Everyone’s favorite planet finding telescope continues to impress. In this morning session, we heard highlights about how the repurposed Kepler mission (K2) is contributing to research in areas ranging from nearby brown dwarfs to extragalactic supernovae. The session kicked off with an overview by Knicole Colon, who happily reported extended funding for K2 through 2018, when its fuel is projected to run out.

Bradley Tucker discussed recent extragalactic results from K2, and supernovae in particular. So far, the Kepler Extragalactic Survey has found 17 supernovae and they hope to find at least 20 more in the next three years. Because Kepler observations are so frequent, they reveal previously hidden subtleties in how supernovae fade over time.

Of course, exoplanet science is still a primary goal for the K2 team. Matthew Penny updated us on the status of the in-progress microlensing campaign, which uses Kepler to search for one-off brightening events that indicate the presence of a planet due to gravitational microlensing. Work is also underway by Jeffrey Coughlin and colleagues to improve our ability to automatically detect and confirm exoplanet candidates with the traditional transit technique. They have developed a robotic technique called DAVE (Discovery And Vetting of K2 Exoplanets), which does an impressive job of eliminating false positive eclipse signals. To complement K2 observations of exoplanet transits, astrobites alumna Courtney Dressing presented a method which incorporates observations from the infrared Spitzer Space Telescope to better refine planet properties such as radius.

One of the challenges of K2 compared to Kepler is noise introduced by the spacecraft’s less precise ability to point. Derek Buzasi implored us to not consider any one pipeline that removes this jitter as necessarily “best,” but rather to try several and recognize that different science goals will need different approaches to data processing.

Jeffrey Van Cleve showed examples of what can be accomplished when K2 data is appropriately processed: just like Kepler, K2 can use asteroseismology to see the ringing oscillations of acoustic waves inside evolved stars.

Finally, several speakers including Buzasi presented their work on stellar astrophysics with K2. In addition to stellar activity and asteroseismology, presenters discussed spots and flares on cool brown dwarfs (John Gizis) and using eclipses together with stellar models to measure distances to star clusters (Keivan Stassun). Not a bad roundup for a broken space telescope!

103: Galaxies Big and Small (by Ben Cook)

This session (one of the first parallel sessions of the conference) included a variety of presentations studying galaxies, primarily using observations but ending with a unique purely analytical study. Stephen McNeil began the session by discussing a survey looking for dwarf galaxies in “voids” the most empty spaces in the universe. Candidate objects can be looked for using a smart choice of photometric color bands, but more work is ongoing to confirm the locations of (and distances to) the objects with spectroscopy. Aaron Romanowsky gave an overview of the field of Ultra-Diffuse Galaxies, a new class of galaxies only discovered within the last 2 years. Some of these galaxies are as large as the Milky Way and seem to have almost as much dark matter, but they contain 1000x fewer stars.

A high-redshift galaxy which is "gravitationally lensed" by a large cluster is shown to the left. The right image shows how big it would look without the magnification. [Slide by Greg Walsh]

A high-redshift galaxy which is “gravitationally lensed” by a large cluster is shown to the left. The right image shows how big it would look without the magnification. [Slide by Greg Walsh]

Greg Walsh presented a longer “dissertation presentation” on his work observing dusty star-forming galaxies. One of the best tools for this job is using galaxy clusters as gravitational lenses to help magnify very distant galaxiesTianxing Jiang showed a variety of observations and simulations that suggest that the level star formation in a galaxy may have to do with the amount of gas pressure, and Aaron Barth showed new measurements of the masses of Super Massive Black Holes using radio measurements. Barth argues that the key to getting good (10%) accuracy is having very high spatial-resolution.

Bill Forman discussed how many galaxies have extremely hot, ionized gas surrounding them, and Bruce Rout argued that dark matter may not be necessary to explain the rotation curves of galaxies; a complicated analytical model using general relativity can do the job without any dark matter at all.

Press Conference: Exoplanets and Brown Dwarfs (by Susanna Kohler)

The first press conference of the meeting featured four speakers discussing some of the latest developments in the field of exoplanet and brown dwarfs.

rocky body surface

Artist’s impression of the surface of a massive, planet-like body being devoured by a white dwarf. [A. Hara/C. Melis/W. M. Keck Observatory]

First up was Carl Melis (UC San Diego), who discussed the discovery of a rocky exoplanetary body currently being shredded by a white dwarf. As the white dwarf’s strong gravitational pull tears the body apart, we can observe the material pulled from its surface layers. These observations — made by Keck Observatory and Hubble — indicate that the body might have been Earth-like, with an outer surface of made up of limestone. Here’s the press release.

Next, Avi Shporer (NASA Jet Propulsion Laboratory) spoke about the first transiting brown dwarf found in K2 mission data. Stars like companionship, but the companions are usually other massive stars, or Jupiter-size or smaller planets. Companions with the mass and size of brown dwarfs are uncommon, leading to the term “brown dwarf desert”. The brown dwarf found by K2 marks the 12th transiting brown dwarf we have discovered.

Jerome Orosz (San Diego State University) was up next, presenting the largest and longest-period circumbinary planet yet discovered. This planet is in an orbit with a 3-year period around a two-star binary system (think Tatooine!). This is the longest orbital period of any confirmed transiting exoplanet, and this Jupiter-sized planet, which is in the circumbinary’s habitable zone, is the largest circumbinary planet we’ve observed. Here’s the press release.

Finally, Sean Mills (University of Chicago) spoke about Kepler-108, a giant planet system in which the two exoplanets don’t orbit within the same plane. This is detectable because the transits of these planets occur at different times and have different depths in the light curve each time they orbit. Their misalignment may have been caused by a past collision with another planet, which was kicked out of the system in the process.

The LIGO-VIRGO Forum on Hunting Gravitational Wave Counterparts (by Gourav Khullar)

This parallel session, organized by Peter Shawhan (University of Maryland, advancedLIGO) discussed the first major followup campaign of the GW150914 gravitational wave (GW) discovery event by the physics and astronomy community around the world. It was extremely exciting to hear the speakers talk of the actual process behind the mega-collaborative effort following the first GW event. news_project_07032016b_lgThis paper, published on June 3rd this year, was described by Peter, with a strong emphasis on the timeline following the GW alert in raw LIGO data back in September 2015, along with description of the sky map and raw data given to different facilities and collaborations that LIGO-VIRGO had signed Memorandums of Understanding (MOUs) with for rapid and robust followups. The talk also focussed on resources and tutorials available now to unpack and characterize future alerts data from LIGO-VIRGO. This talk was followed by the description of the all sky survey PAN-STARRS, and its joint efforts with LIGO. It was pointed out that PAN-STARRS had already scanned the sky multiple times, which gave the program an edge in determining transients, i.e. recent features appearing on their new maps but not the old. This extensive survey also allowed better characterization of the transient source, which would be the next step for PAN-STARRS and other similar projects.

Following this was a talk by Andy Howell, of the newly formed Las Cumbres Observatory – A Global Telescope Network (LCOGT), made up of multiple telescopes across the US, Chile, Spain, South Africa, China and Australia. Howell emphasized that a robotic pointed-search facility could be extremely crucial in automated alert triggering of GW events in the future. Their galaxy and transient catalog is one to look out for.

Greetings from the 228th American Astronomical Society meeting in San Diego, California! This week, along with a team of fellow authors from astrobites, I will be writing updates on selected events at the meeting and posting twice each day. You can follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

If you’re at the meeting, come stop by the AAS booth (Booth #211-213) to learn about the newly-announced partnership between AAS and astrobites and pick up some swag. And don’t forget to visit the IOP booth in the Exhibit Hall (Booth #223) to learn more about the new corridors for AAS Journals and to pick up a badge pin to represent your corridor!


eclipse corona

Editor’s note: This week we’re in Boulder, Colorado at the 47th meeting of the AAS Solar Physics Division (SPD). Follow along to catch some of the latest news from the field of solar physics!

Yesterday’s press conference was titled “Preparing for the 2017 Great American Eclipse.” Four speakers highlighted both outreach and research projects that are planned for the eclipse that will cross the continental United States on August 21st next year.

Eclipse from High Altitude

First up, Angela Des Jardins (Montana Space Grant Consortium) introduced us to the nationwide Eclipse Ballooning Project.

ISS eclipse

An eclipse as seen from the ISS. Being up high gives you a very different perspective on eclipses! [NASA]

The last total solar eclipse in the continental United States was in 1979, and people were told to stay inside and watch from their TVs! For the next total solar eclipse in the US, we want the opposite: for everyone to be outdoors and in the path of totality to watch (with eclipse glasses — let’s be safe)! This eclipse is a fantastic educational opportunity, and a way to reach an enormous audience.

And what better way to experience the eclipse than to be involved? The Eclipse Ballooning Project is involving more than 50 student teams from 30 states to fly high-altitude balloons at 20 locations along the total eclipse path. These balloons will send live videos and images from the edge of space to the NASA website.

Why? Being someplace high up provides an entirely different view for an eclipse! Instead of looking up to watch the Moon slide in front of the Sun, you can look down to watch the Moon’s shadow race across the Earth’s surface at thousands of miles per hour. This unique perspective is rare, and has certainly never been covered live. This will be an awesome addition to other coverage of the eclipse!

At Maximum Totality

The next speaker, Gordon Emslie, described the outreach efforts planned at his institution, Western Kentucky University (WKU). The location where the eclipse totality will last the longest — 2 minutes and 40 seconds — is the small town of Hopkinsville, KY. WKU is located a little over an hour away, and both locations are prepared for a large influx of people on eclipse day!

Partial solar eclipse as viewed by the space-based Solar Dynamics Observatory. [NASA/SDO]

Partial solar eclipse as viewed by the space-based Solar Dynamics Observatory. [NASA/SDO]

WKU is located just off the centerline of eclipse path, which has some advantages: this provides better viewing of some of the chromospheric features of the Sun during the eclipse, like priminences and solar loops. WKU is setting up a variety of educational and public outreach activities at their football stadium and the WKU farm, and they encourage you to come visit for the eclipse!

In addition, they are participating in a nationwide experiment called Citizen CATE, short for the Continental American Telescopic Eclipse. This project will use 60 telescopes spanning the 2500 mile path of totality to record continuous data of the eclipse as it travels across the US. The result will be data of a remarkable 90 minutes of totality, revealing the activity of the solar corona and providing an extended view of the eclipse as has never been seen before.

Science During the Eclipse

Next up was Shadia Habbal (University of Hawaii), who is a co-leader of the AAS 2017 Eclipse Task Force. In addition to her education and outreach efforts associated with the eclipse, however, Habbal is a solar eclipse researcher. She and her collaborators are known as the Solar Wind Sherpas, due to the fact that they hand-carry their science equipment around the world for solar eclipses!

Solar corona during a 2008 eclipse, with color overlay indicating emission from highly ionized iron lines. [Habbal et al. 2010]

Solar corona during a 2008 eclipse, with color overlay indicating emission from highly ionized iron lines. [Habbal et al. 2010]

The primary science done during solar eclipses is the study of the solar corona, the region that extends from the solar surface out to several solar radii. This region is too faint to observe normally, but when the light from the Sun’s disk is blocked out, we can examine it.

Unfortunately, the space telescopes that observe the Sun all have relatively narrow fields of view. But during an eclipse, we can gain the larger context for the corona with ground-based observations, with the Moon conveniently blocking the light from the Sun’s disk! The cover photo is a spectacular example of this.

Observations of the corona during eclipses can provide information on both enormous events, like coronal mass ejections, and faint dynamical features, like plasma instabilities and expanding loops. In addition, we can learn about the plasma properties by examining emission from highly charged ions. The upcoming eclipse should provide a great opportunity to do some coronal science!

A Unique Opportunity

The final press-conference speaker for the meeting was Jay Pasachoff (Williams College and Caltech), a veteran solar eclipse observer who was able to speak to what we could expect if we make it into the path of totality next year.

eclipse path

Path of totality across the continental US for the August 2017 eclipse. [Fred Espenak/NASA GSFC]

Pasachoff pointed out that there are nearly 12 million people located within the band of totality. There are probably another 200 million within a day’s drive! He strongly encouraged anyone able to make it to the path of totality to do so, pointing out that the experience in person is completely unlike the experience of watching a video. The process of watching the world around you go dark, he says, is something that simply isn’t captured when you watch an eclipse on TV.

If you plan to travel for the eclipse, Pasachoff’s recommendation is to aim for the northwest end of the path of totality, rather than the southeast end — surprisingly, weather statistics suggest you have a better chance of not getting clouded out in the northwest.

We now have a year left to educate everyone likely to view the eclipse on when and how to view it safely! Accordingly, Pasachoff concluded the conference by providing a series of links on where to find more information:



Editor’s note: This week we’re in Boulder, Colorado at the 47th meeting of the AAS Solar Physics Division (SPD). Follow along to catch some of the latest news from the field of solar physics!

Yesterday’s press conference provided an excellent overview of some of the highlights of this week’s SPD meeting. Four speakers provided their views on some of the hottest topics in solar physics at the moment, including “stealth” coronal mass ejections (CMEs), sunspot formation, long-term solar-activity trends, and the largest solar telescope ever built.

Stealth CMEs


Solar and Heliospheric Observatory (SOHO) composite image of a coronal mass ejection. [ESA/NASA/SOHO]

First up, Nathalia Alzate (Aberystwyth University) talked about recent success in solving the mystery of so-called “stealth” CMEs, massive solar storms that don’t exhibit the usual clues to their origin. Most CMEs have low-coronal signatures like flares, filament eruptions, jets, etc. that reveal the origin of the CME at the Sun. But stealth CMEs appear without warning, and seem to have no evidence of low-coronal signatures.

But are these signatures not there? Or could we just be missing them? Alzate and her collaborator Huw Morgan used advanced image processing techniques to search for low-coronal signatures associated with 40 CMEs that have been classified as stealth CMEs. Their techniques enhance the observed structure down to fine spatial scales, and help reveal very faint dynamic events.

Sure enough, these processing techniques consistently revealed low-coronal signatures for every single supposed stealth CME they examined. This suggests that all CMEs exhibit some signatures in the low corona — it’s only a matter of being able to process the images well enough to detect them!

Spectacular Sunspot Simulations

Still image from a simulation studying sunspot formation. Compare to the cover image of sunspot observations! [Feng Chen, Matthias Rempel, & Yuhong Fan]

Still image from a simulation studying sunspot formation. Compare to the cover image of sunspot observations! [Feng Chen, Matthias Rempel, & Yuhong Fan]

Next up, Feng Chen (High Altitude Observatory) described recent computational advances in simulating sunspot formation. He and his collaborators have used high-performance computing to build a model that successfully reproduces many of the key properties of sunspots that are observed.

In particular, these simulations track the motions of the magnetic field starting within the interior of the Sun (8000 km below the surface!). The magnetic field is generated and intensified by convection deep within the solar interior. Bundles of magnetic field then rise through the convection zone, eventually breaking through the solar surface and giving rise to sunspots.

This process of tracking the flow as it travels from the convective layer all the way through the solar surface has resulted in what may be some of the highest fidelity simulations of sunspots thus far. The structures produced in these simulations compares very favorably with actual observations of sunspots — including the asymmetry seen in most sunspots.

Counting Spots on the Sun

Continuing the discussion of sunspots, Leif Svalgaard (Stanford University) next took us on a historical journey from the 1600s through the present. For the last 400 years — starting with Galileo — people have kept records of the number of sunspots visible on the Sun’s disk.

Galileo sunspots

One of Galileo’s drawings of his sunspot observations from 1612. [The Galileo Project]

This turns out to be a very useful practice! Total solar irradiance, a measure used as input into climate models, is reconstructed from sunspot numbers. Therefore, the historical record of sunspots over the last 400 years impacts our estimates of the long-term trends in solar activity.

Based on raw sunspot counts, studies have argued that solar activity has been steadily increasing over time. But could this be a misinterpretation resulting from the fact that our technology — and therefore our ability to detect sunspots — has improved over time? Svalgaard believes so.

By studying and reconstructing 18th century telescopes, he demonstrates that modern-day sunspot counts are able to detect three times as many sunspots as would have been possible with historical technology. When you normalize for this effect, the data shows that there has therefore not been a steady increase long-term in sunspot numbers.

World’s Largest Solar Telescope

The final speaker of the press conference was Joe McMullin (National Solar Observatory), who updated us on the status of the Daniel K. Inouye Solar Telescope (DKIST). This 4-meter telescope will be the world’s largest solar telescope, and the first new solar facility that the US has had in several decades.

The DKIST team and facilities, as of March 2016. [NSO]

The DKIST team and facilities, as of March 2016. [NSO]

The technology involved in this spectacular telescope is impressive. Its thin, enormous mirror is polished to within an error of nearly 1/10,000th of a human hair! Underlying the telescope is the most complex solar adaptive optics systems ever created, with 1600 different actuators controlling the system real-time to within an error of 4 nanometers. In addition, the entire facility is designed to deal with a tremendous heat load (which can severely limit the quality of observations).

DKIST’s construction on Haleakala in Hawaii has been underway since 2012, and is making solid progress. The majority of the structures have now been completed, as have most of the major telescope subsystems. The primary hurdle that remains is to integrate all the of components and make sure that they can perform together — no small feat!

DKIST is expected to begin science operations in 2020, with ~10-20 TB of data being produced each day. This data will be freely and immediately accessible to both researchers and the public.


X-ray Sun

Editor’s note: This week we’re in Boulder, Colorado at the 47th meeting of the AAS Solar Physics Division (SPD). Follow along to catch some of the latest news from the field of solar physics!

The 2016 SPD meeting was launched this morning from the University of Colorado Boulder campus. Two of the hot topics at this year’s meeting include celebration of the recent move of the National Solar Observatory’s headquarters to Boulder, and discussion of the future Daniel K. Inouye Solar Telescope (DKIST, formerly the Advanced Technology Solar Telescope, ATST). DKIST, planned for a 2019 completion in Hawaii, is the next big telescope on the horizon for solar physics.

Today’s press conference had an interesting focus: instruments providing new high-energy observations of the Sun. Representatives from four different instruments were here to talk about some of the latest X-ray solar observations.



The GRIPS payload flew at 130,000 ft over Antarctica on a giant balloon in January 2016. [NASA/Albert Shih]

First up, Albert Shih (NASA Goddard) described the Gamma-Ray Imager/Polarimeter for Solar flares, or GRIPS. GRIPS is a balloon-borne instrument designed to detect X-rays and gamma rays emitted during solar flares. Up to tens of a percent of the energy in solar flares is emitted in the form of accelerated particles, but the physics behind this process is not well understood. GRIPS observes where the highest-energy particles are accelerated, in an effort to learn more about the process.

GRIPS was launched on 19 January, 2016 and flew for roughly 12 days — gathering ~1 million seconds of data! The logistics of this instrument’s flight are especially interesting, since it was launched from Antarctica and carried by a balloon at a whopping elevation of 130,000 ft (to get high enough that the atmosphere doesn’t absorb all the photons GRIPS is trying to observe). Though the data from the mission has been retrieved, the bulk of the hardware remains where it landed at the end of January. It must wait for the warmer Antarctic weather in December before a team will be able to reach the instrument and recover it!

Over the 12 days it flew, GRIPS observed 21 small, C-class solar flares. Data analysis is currently underway, and the team hopes that these observations will help improve our understanding of the processes underlying these solar flares.


The FOXSI mission launches on a sounding rocket, taking roughly five minutes of hard X-ray data of the Sun during its flights. [NASA/FOXSI]


Next, Camilo Buitrago-Casas (UC Berkeley) introduced us to the Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket. More than anything, FOXSI is a test of new instrumentation that may be key to future observations of the Sun in hard X-rays.

FOXSI is a focusing telescope — something that is significantly more difficult to do with hard X-rays than it is with optical telescopes. Hard X-rays are difficult to bounce off of mirrors since, due to their high energy, they simply pass through the mirrors! The trick is to capture the X-rays at a grazing angle, sending them through a series of nested mirrors that progressively focus the light. Due to this process and new-technology detectors, FOXSI is able to produce very high-quality, low-noise images of some of the hottest solar sources in fine detail.

FOXSI has now flown twice, with a third flight planned for 2018. Each flight gains about five minutes of data while the sounding rocket is above the Earth’s atmosphere in its parabolic trajectory. While this instrument has already produced a wealth of data about tiny solar flares, the ultimate goal is to get FOXSI’s technology on a space-based observatory, allowing for dedicated and longer observations of solar flares.


Next, Lindsay Glesener (University of Minnesota) spoke about the Nuclear Spectroscopic Telescope Array (NuSTAR) space telescope, which actually has this opportunity for long solar observations — except that it’s a little busy. NuSTAR was primarily designed to look at faint sources in the distant universe. But a few times a year, it takes a few hours to look closer to home, turning to point at the Sun.


Artist’s concept of NuSTAR, a high-energy space telescope that occasionally takes a break from observing the distant universe to instead point at the Sun. [NASA]

Due to NuSTAR’s extreme sensitivity, there are obviously some challenges in pointing it directly at a nearby, high-intensity source! Large solar flares would completely swamp the telescope’s detectors, but in quiet conditions, NuSTAR is an excellent tool for detecting faint sources.

As a result, NuSTAR recently detected the smallest, faintest X-ray flare ever imaged at high energies. Tiny flares such as this one are very different from the enormous eruptions we’re used to seeing in solar images; these small flares would go unnoticed by a less sensitive instrument. They’re interesting to study, however, because they might provide the solution to the “coronal heating problem” — the question of how the enormous temperature of the solar corona is sustained. It’s thought that continuous eruption of small solar flares could potentially provide the heating necessary to explain the corona’s temperature.


The last speaker of the press conference was Amir Caspi (Southwest Research Institute), who told us about the Miniature X-ray Solar Spectrometer, or MinXSS. MinXSS is a NASA-funded CubeSat — a small but full-feature satellite roughly the size of a loaf of bread. It was deployed from the International Space Station just two weeks ago (16 May), and saw its first light last night (30 May)!

MinXSS will detect soft X-rays from the Sun, with the goal of gaining a better understanding solar flares, nanoflares, and how these impact the Earth. When solar X-rays are absorbed by the Earth’s upper atmosphere, the atmosphere heats up — with photons of different energies causing heating in different atmospheric layers. Understanding this interaction is important for making predictions about how communications signals traveling through the Earth’s ionosphere might be affected.

MinXSS’s mission is roughly 6-12 months long, with a second mission planned after the conclusion of the current one. The team is looking forward to MinXSS’s entry into science mode in a few days time, and the data that will hopefully follow! You can keep up with the latest news from MinXSS on facebook and twitter.


Check out the gif below that shows the deployment of MinXSS (the one in front) and a second CubeSat, CADRE, from the ISS! This compilation of photos was put together by James Mason, MinXSS project manager. The photos were taken from the ISS by astronaut Tim Peake. [NASA]


Sun and Heliosphere corridor

In the lead-up to next week’s 2016 Solar Physics Division (SPD) meeting, we wanted to introduce you to Leon Golub, our new Lead Editor for the Sun and the Heliosphere corridor.

Leon is a Senior Astrophysicist in the High Energy Division at the Harvard-Smithsonian Center for Astrophysics. He specializes in studies of solar and stellar magnetic activity, and he has built numerous rocket and satellite instruments to study the Sun and its dynamic behavior.

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Tell me about your field of research and some of your current projects.

I’ve been working primarily on understanding the dynamics of the solar corona, especially using new types of instrumentation that can provide challenges to our theoretical understanding.


Image of the Apollo Telescope Mount on Skylab. [NASA]

Why did you choose this field?

Shortly after graduating from MIT in experimental high energy physics I found a position with a group that was preparing to launch an X-ray telescope on Skylab as part of the cluster of solar instruments called the Apollo Telescope Mount. I have stayed with that field and related ones ever since.

What do you consider to be some of the biggest open questions in solar and heliospheric research today?

There are so many major questions that it’s difficult to just settle on a few. The heliosphere is defined by the extent of the influence of the Sun on the interstellar medium. It is an exciting time in that area of study, because we now have the ability to make impressive new observations that allow us to test our understanding of that outer boundary.

Within those limits, the Sun has a major influence on solar system objects via its gravitational pull, its light and heat, and the magnetized plasma and high energy particles that it emits in all directions. We are making major discoveries related to how the Sun has influenced the formation and evolution of the planets, including our own planet.

The source of all this influence is, of course, the Sun itself, and we are working to understand how magnetic fields are generated inside the Sun and how they produce the observed dynamic processes once they emerge from inside.


A coronal mass ejection observed by the LASCO C3 instrument on the Solar and Heliospheric Observatory. [NASA/ESA/SOHO]

What do you anticipate will be some of the most exciting topics presented on at the SPD meeting next week?

We have some new and exciting presentations that I’m looking forward to, related to solar magnetism and solar dynamics, especially flares and mass ejections. There are also some spectacular developments going on in improving the quality of ground-based observations, normally limited by the murkiness of our atmosphere. I expect to see some thrilling new observations from them.

What do you do in your work for ApJ?

I am one of the new Lead Editors, heading the Solar and Heliospheric corridor. This is a new level of editorial work situated between the Editor in Chief and the Scientific Editors (SEs). I am also acting as an SE myself, along with the other Solar and Heliospheric SEs.

What do you think makes for a well-authored paper?

I have long thought that a training in journalism is the best preparation for authoring scientific papers. What is your headline? Can you inform the reader succinctly and clearly?

Is there anything else you’d like to share about the publishing process with potential authors?

I would tell potential authors that our primary goal is to help them publish high quality work, and that the review process is critical to that effort. It takes time, but it makes all the difference.

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Look for Leon and several of the Scientific Editors for the corridor at the SPD meeting in Boulder next week! Additionally, Leon can be reached by email should you have any questions about the new Sun and Heliosphere corridor.

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