Greetings from the 230th American Astronomical Society meeting in Austin, Texas! This week, along with author Benny Tsang from Astrobites, I will be writing updates on selected events at the meeting and posting at the end of each day. You can follow along here or at astrobites.com. The usual posting schedule for AAS Nova will resume next week.

Want to get a head start before the #AAS230 plenaries begin? You can read brief interviews with the plenary speakers over at Astrobites.

We hope to see you around at Austin! Drop by and visit AAS, AAS Journals, and Astrobites at the AAS booth in the Exhibit Hall (Booth #18) to learn more about AAS’s new publishing endeavors, pick up some Astrobites swag, or grab a badge pin to represent your AAS journals corridor!

Editor’s Note: This week we’re at the 229th AAS Meeting in Grapevine, TX. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting 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.

AAS Hack Day (by Joanna Bridge)

Today was the #AAS229 Hack Day! Hack Day, this year sponsored by Northrop Grumman, has occurred on the final day of AAS conferences for several years now. About 50 astronomers gathered together to combine their extensive brain power to work on projects pitched by various people in the room. These projects ranged from in-depth coding to sewing, the common thread being simply that we created.

A comprehensive list of the projects undertaken today will be found here as participants add their hacks to the site. If you want to follow the progress as it occurred, check out the Twitter hashtag #hackAAS. Here is a list of some of today’s accomplishments:

• Composing letters to your politicians
• Solving differential equations numerically using basis functions
• Getting tests to work in astropy with a new version of pytest
• Creating a repository of hacks from Hack Day for future reference
• Overlaying K2 postage stamps with SDSS images
• Building a database with literature on inclusivity for easy access
• Planning and budgeting for the revitalizing of an unused planetarium at City College of New York
• Saving PNG plots with metadata in python
• Sewing extravaganza using cloth posters and other fabrics – bowties, infinity scarves, bibs, bags, hair accessories, and capes!

#hackAAS was a success! Enjoyed working with @reneehlozek, Casey, and Frank hacking together a database for reading on #inclusivity #aas229

— Joanna Bridge (@bojibridge) January 7, 2017

.@SeeTheStarsRise and @victoriadi2MASS presenting our #hackAAS project on reviving the CCNY planetarium! pic.twitter.com/wHfYkRr97G

— Danny Barringer (@HeavyFe_H) January 7, 2017

From #hackaas: @betsyhern4 covered the #aas229 bag using my Frontier Fields image and the Enterprise! #aas229 pic.twitter.com/LrHKMx0WZR

— Rachael Livermore (@rhaegal) January 8, 2017

See the stream of the results on Periscope from this tweet:

#hackaas project results #aas229 https://t.co/IYOkmfkfvw

— Geert Barentsen (@GeertHub) January 7, 2017

Hack Day was a great success and I personally cannot wait for the next one!

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Lancelot M. Berkeley Prize: Exploring for Galaxies in the First Billion Years with Hubble and Spitzer ‐ Pathfinding for JWST (by Ashley Villar)

Garth Illingworth kicked off the final day of #AAS229 with the Lancelot M. Berkeley Prize lecture on very, very old galaxies. He specifically studies the formation (or ‘build-up’) of these galaxies at very large redshifts of ~10 (just 500 million years after the big bang!) using telescopes like the Hubble Space Telescope (HST) and Spitzer.

Although these young galaxies are small (and often unresolved), large surveys have allowed Illingworth and others to better understand statistical properties of the early galactic populations as functions of time. As one example, the luminosity function of these galaxies (the number of galaxies as a function of brightness) becomes extremely steep at the faint end of galaxies. This luminosity function can be compared to a star formation history as a function of redshift. At large redshift, Illingworth points out that the luminosity seems to agree with the star formation histories, meaning that reddening from dust has a small effect at high redshifts.

Looking forward, Illingworth is excited about the next generation space missions, including JWST and WFIRST. Both will have the capacity to study the very earliest galaxies and the buildup of galaxies over the course of cosmic time. JWST launches in 2018, so exciting results are just around the corner!

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Press Conference: Black Holes, Green Galaxies, Old Stars & NuSTARs (by Susanna Kohler)

The second-to-last press conference of the meeting was, as AAS Press Officer Rick Fienberg put it, an “astronomical potpourri” covering a discovery in a protoplanetary disk, nearby black holes, measurements of the Milky Way’s mass, and distant galaxies.

The first briefing was given by John H. Debes (Space Telescope Science Institute), who discussed how an old instrument on Hubble, the Space Telescope Imaging Spectrograph (STIS), was used to make a new discovery around a nearby star. Observations from STIS revealed an asymmetry rotating around the disk of gas and dust surrounding TW Hydrae, a stellar system located ~200 light-years away from us. The asymmetry had a 16-year rotation period, which is too fast for it to be a feature actually moving within the disk. Instead, astronomers have proposed that it is a shadow cast on the outer disk by a potentially misaligned inner-disk region. They calculate that the warping of the disk could have been caused by the presence of a Jupiter-mass planet orbiting in a gap at ~1 AU from the central star. For more information, check out the press release here.

Next up was a tag-team of Ady Annuar (Durham University, UK) and Peter Boorman (University of Southampton, UK), who presented on two nearby supermassive black holes that have been recently imaged directly for the first time. IC 3639 and NGC 1448 are galaxies located at 170 million and 38 million light-years away, respectively, and they both contain supermassive black holes at their cores. These black holes have remained undiscovered until recently, however, because they are heavily obscured by a surrounding torus of the gas and dust that feeds them. Because we are viewing these two galaxies edge-on, the obscuring torus prevents us from seeing the black holes. NASA’s X-ray telescope NuSTAR (Nuclear Spectroscopic Telescope Array), however, was able to examine these galaxies and identify the black holes feeding on material at their centers — and even provide more information about the gas and dust shrouding them. Read more in the press release here, and check out below an awesome animation that Boorman showed us: an artistic rendering of a torus rotating around a supermassive black hole. [Made by Ricardo Ramírez based on a publication led by Marko Stalevski]

The third presentation, given by Gwendolyn Eadie (McMaster University), discussed recent efforts to measure the mass of our galaxy. One of the best ways to estimate how much mass the galaxy contains — including dark matter, which can’t be detected directly — is to measure the velocities of globular clusters bound to the galaxy (whose orbits are determined by the gravitational pull of the Milky Way). Unfortunately, our measurements of these velocities are incomplete: some proper motions of Milky Way globular clusters aren’t yet known. Eadie and collaborators have made clever use of Bayesian statistics to use the values we do know — as well as the uncertainties about those we don’t — to make new, more accurate estimates of our galaxy’s mass, finding that the Milky Way contains a mass of roughly 400–580 billion solar masses. More info can be found here.

The final briefing was given by Matthew Malkan (University of California, Los Angeles) on the subject of young galaxies in the early universe. A recent examination of thousands of distant galaxies in the Subaru Deep Field yielded the discovery that all small galaxies are very strong emitters of the green emission line of doubly-ionized oxygen. This emission is surprising, as only extremely energetic X-ray photons can cause this double ionization — and few such high-energy photons are produced by young stars in modern galaxies. Malkan postulates that the early generations of star formation we’re viewing in these distant, small galaxies produces much hotter stars. You can read more about the discovery in the press release hosted here.

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Seminar for Science Writers: The August 2017 All-American Solar Eclipse (by Natasha Batalha)

The second press conference of the day covered the exciting science and the logistics of the August 21, 2017 total solar eclipse. The path of this eclipse sweeps across the entire United States, which is incredibly rare. Although total solar eclipses happen every year, they are usually only visible in non-populated areas such oceans or arctic regions. In fact, this marks the first eclipse to grace the continental U.S. since 1979 and the first to go coast-to-coast since 1918!

The first talk by Jay Pasachoff, from Williams College, covered some of the science that can be done during the eclipse. His group will study the dynamics of the solar corona and the frequency of oscillations as seen through special coronal filters. Many people are very surprised to hear how many questions about the Sun are still unanswered. For example, we still don’t fully understand why the corona is millions of degrees hotter than the surface of the Sun. We usually attribute it to the Sun’s magnetic field, but it’s not entirely clear how. The natural ability of the Moon to block out the Sun offers scientists an opportunity that would otherwise be very technologically complex. Given the cover photo image at the top of the page, it’s easy to see how!

Next up, Alex Young from NASA Goddard Space Flight Center explained the efforts that NASA and other large agencies will be providing. NASA’s goals during the total eclipse will be to engage and educate the public, as well as support all the work being done in the nation. NASA will also collaborate with the AAS and NSF to promote safety. Both NASA and AAS have websites with resources so you can start planning your August 21 vacation.

Although there is much to be excited about, Angela Speck from University of Missouri explained some of the challenges that we will encounter. First off, we need to start communicating to the public about how rare this event is. There are only 12 million people in the U.S. that don’t need to drive. But, Dr. Speck pointed out that 99% of the U.S. is within a long day’s drive to a total eclipse area. Major cities in the total eclipse zone, such as Nashville, have the potential to be wildly packed.

Lastly, AAS’s very own Rick Fienberg expanded on some of the eye safety facts the public should and should not be concerned with. A total solar eclipse is about as bright as the full moon and just as safe to look at (even with binoculars or a telescope). But during the partial eclipse times there is a genuine risk of retinal injury. However, there are still some pretty high misconceptions regarding this. Here are the major ideas you should communicate to your friends and family:

1. Sunglasses cannot be worn in place certified solar viewing glasses
2. Retinal injury is actually quite uncommon, although we do not advise any prolonged Sun-staring
3. The Sun does not emit dangerous rays during a solar eclipse and the Moon does not have any focusing effects

This solar eclipse might be a once in a lifetime event, so start planning your trips now!

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The 2017 Total Solar Eclipse: Through the Eyes of NASA (by Michael Zevin)

Start counting down the days until August 21, 2017. On this special day, we will have the first total solar eclipse to hit mainland U.S. in almost 40 years, and its band of totality will darken a 70-mile stretch of Earth all the way from Oregon to South Carolina. Today’s plenary talk by C. Alex Young, the Associate Director for Science at NASA Goddard Space Flight Center, ignited excitement in all the astronomers in the room for the upcoming astronomical phenomenon.

Young himself admitted that he has never seen a total solar eclipse. Surprisingly, he was far from alone. Even in a room full of astronomers, the vast majority conceded when asked who has never seen totality. However, starting with the eclipse in August, Young is “looking forward to becoming a total eclipse junky.” Young started by showing movies of previous solar eclipses, and the sheer awe and exhilaration that it induced on the lucky observers who documented the events. Young displayed a quote by David Baron, author of American Eclipse, who describes the experience perfectly: “For three glorious minutes, I felt transported to another planet, indeed to a higher plane of reality, as my consciousness departed the Earth and I gaped at an alien sky.”

The eclipse in August 2017 will cast a shadow about 70 miles wide and traverse from the Pacific to the Atlantic coastline in just about 1.5 hours. To get the longest view, I recommend renting a supersonic jet plane and following beneath the shadow at a blazing 2000 miles an hour. However, for most people that are forced to stay stationary, totality will last about 2 minutes.

We used precise measurements of Earth and the moon to make the most accurate map of #Eclipse2017: https://t.co/gY3wE3qdHF pic.twitter.com/jq5UJR9kCA

— NASA Sun & Space (@NASASun) January 7, 2017

Young showed some of the great visualizations that NASA has been producing for this eclipse, including a great animation showing how the solar energy impacting the Earth changes during the eclipse. Because of the blocked sunlight, the temperature is expected to rapidly drop 5-15 degrees during totality, which Young says will affect the wildlife, certain types of vegetation, and small scale weather.

Lastly, Young implored the astronomical community to take part in this historic event! By visiting eclipse2017.nasa.gov, one can see the path of totality (which traverses many national parks) and find the best places to view the eclipse. As astronomers, Young asked that we connect our science to the eclipse and take part in the many outreach efforts that will be underway. Exoplanet transits, coronal activity around AGN, and many more research topics can be connected to our Sun’s special day. Mark your calendars and buy your solar glasses so you can see the darkness on August 21st!

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Plenary Session: How Supermassive Black Hole Feedback Might Work (Ashley Villar)

Megan Donahue finished up the conference with a fascinating talk on supermassive black hole feedback. We now believe that almost all galaxies have supermassive black holes in their centers. However, the relationship between the growth and activity of the black hole and its surrounding gas is still an active field of research. You might be wondering what gas we are talking about. When you imagine the anatomy of a spiral galaxy, you probably think of the flat disk and the central bulge, but there is also a huge amount of cold gas surrounding most galaxies which is known as its circumgalactic medium (CGM). This CGM contains most of the galaxy’s baryons and metals.

Active galactic nuclei (AGN), or active black holes in galaxies, interact with the CGM in such a way that, as Donahue puts it, the galaxy is “marginally stable to condensation.” In other words, the AGN will become active and overheat the CGM which decreases precipitation onto the AGN and cools the system. Once cooled, star formation increases and reheats the system, again activating the AGN. Donahue quantifies this cycle using the ratio between the so-called cooling time of the system and the free-fall time. Systems under this theoretical model generally have a ratio of 10:1 for cooling to free-fall times. This is seen in both simulations and real massive galaxies.

This simple theory also reproduces several well-known galactic relations with little to no fitting of free parameters. For example, the theory is able to reproduce the mass-metallicity relation (in which more massive galaxies tend to be more metal-rich), and the M-sigma relation (in which galaxies with larger supermassive black holes have more velocity dispersion in their bulge). While the exact mechanism by which this feedback occurs is uncertain, this new theory seems to at least begin to explain many complex relations we need between galaxies and their central black holes.

Editor’s Note: This week we’re at the 229th AAS Meeting in Grapevine, TX. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting 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.

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SPD George Ellery Hale Prize: Magnetic Energy Release in Solar Flares (by Josh Fuchs)

#AAS229 Terry Forbes preparing to speak on magnetic energy release in solar flares pic.twitter.com/rTGF4OJWAh

— Brendan Peter Miller (@brendanpmiller) January 6, 2017

Dr. Terry Forbes (University of New Hampshire) is a theorist working to understand solar flares like the one shown above from the Solar Dynamics Observatory. All of these eruptions arise from instabilities of stressed magnetic fields on the surface of the Sun.

New theories must address the light curves of solar flares. In the chromosphere, H-alpha observations of flare “ribbons” demonstrate that these ribbon arise in minutes, then decay over many hours. In the corona, hard X-rays (above ~1 keV) will last less than an hour, but soft X-rays (<1 keV) can persist for a few hours. These timescales are clues to the physical processes at work in solar flares.

Magnetic reconnection is the physical process that seems to explain much of this solar activity. Dr. Forbes has spent most of his career working on the details of magnetic reconnection and using observations to inform the theory. As examples, he showed videos showing how flares grow over 4–5 hours and showing how the relatively hotter and cooler material moves relative to each other.

While the theory has improved significantly over the last few years, there are a few still unanswered questions. Understanding exactly how large the reconnection regions are and searching more thoroughly for slowly propagating shocks are the next discoveries that can push forward our understanding of magnetic activity on the Sun.

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Press Conference: Stars & Interstellar Space (by Susanna Kohler)

The first press conference of the day covered four speakers on topics related to stars and interstellar space. First up was Julia Zachary (Wesleyan University), an undergraduate student who spoke about observations from Hubble and the two Voyager Spacecrafts. Combining the views of these three spacecrafts has allowed astronomers to get both a large- and small-scale view of the interstellar medium that the Voyager spacecrafts are traveling through, providing a broad look at the environment surrounding the spacecraft, as well as more information about the heliosphere that surrounds our solar system and how it adapts to its surroundings. To learn more, check out their press release here.

The third talk was given by Walid Majid (Jet Propulsion Laboratory). Majid spoke on PSR J1119-6127, the “missing link” neutron star. PSR J1119-6127 has been caught behaving both like a radio pulsar and like a magnetar, suggesting that it may be in a never-before-seen transition period between the two states. Pulsars and magnetars have long been believed to be connected, so the discovery of an object that exhibits part-time behavior of both is an important find. Scientists currently believe that the magnetar-like X-ray bursts it exhibited in 2016 (after having behaved very politely like a quiet radio pulsar since 2000) were due to its large magnetic field becoming twisted as the object spun. You can find out more in the press release here.

Finally, Lori Allen (National Optical Astronomy Observatory) concluded the session with a discussion about light-pollution solutions that communities can use. In particular, Allen addressed the issue of outdoor LEDs, which have become an increasing problem as LEDs take over as the dominant source of outdoor lighting. Allen identified several ways to battle light pollution from LED lighting: shielding (point lights downward rather than at the sky), brightness (choose dimmer options when possible), and color (options that are less blue are less disruptive to astronomy, wildlife, etc.). More info is available here.

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Newton Lacy Pierce Prize: The Chemistry of Planet Formation (by Meredith Rawls)

Karin Öberg (Harvard-Smithsonian CfA) gave an excellent prize talk about the many facets of how planets form. Stars with disks are an interesting phase of star and planet formation, and varying chemistry in protoplanetary disks has a big effect on what kind of planets can form. Öberg said that it’s all well and good if we know a planet is in the “habitable zone,” but if it doesn’t have the right material for liquid water, it’s not going to be Earth-like. Her work is possible now thanks to the Atacama Large Millimeter/submillimeter Array (ALMA)’s unprecedented view of planet-forming disks of gas and dust swirling around stars.

Oberg: ALMA has revolutionized our ability to see protoplanetary disks, aka the gas and dust around stars that will form planets. #aas229 pic.twitter.com/rnclygPnwO

— Meredith Rawls (@merrdiff) January 6, 2017

One piece of the protoplanetary disk puzzle is measuring the location of snowlines, or transitional regions where certain molecules freeze out. Different physical processes govern planet formation on either side of a snowline. Knowing the temperature profile of a protoplanetary disk isn’t enough information on its own, however, because chemical composition and particle size also affect where snowlines fall. Therefore, Öberg uses laboratory experiments to figure out which observable molecules trace the positions of carbon monoxide (CO) and other volatile ices and find snowlines.

In the past, our own Solar System formed from a protoplanetary disk much like the ones Öberg studies. It turns out the same molecules that can form ices around protostars are also important in comets! She finds that the kinds of molecules in protoplanetary disks are also present in comets in our own Solar System, and can use deuterated molecules (those that have hydrogen atoms with an extra neutron) to compare planet formation histories. Overall, water is always abundant during planet formation. Other volatile molecules probably arrive with water, but chemistry and turbulence in protoplanetary disks may alter or destroy them.

Öberg’s doesn’t think the chemistry of our Solar System is necessarily special, and says other systems could likely have the same chemical soup. To know for sure, though, we will need to observe more than just a handful of protoplanetary disks and do statistical studies. We also need to keep investigating astrochemistry in the laboratory: for example, how different ices clump together, and what happens when they are exposed to different kinds of light and radiation. The future of protoplanetary disks is bright.

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Press Conference: Exoplanets and Exocomets (by Joanna Bridge)

Today’s press conference on exoplanets and exocomets was started by Eden Girma, from Harvard College. She discussed her research on the possibility that black holes may eject “spitballs,” remnants from stars shredded by the black hole. Disrupted by tidal forces, these stars would become spaghettified, then ejected back into the solar system. Grima’s simulations indicate the 95% of these stellar fragments would be be ejected out of the solar system with hyper-velocities. 90% of the bound fragments would only get as far as 100 parsecs from the black hole. She also performed a calculation to determine the number of fragments within a surveying radius from the Sun, and found that the distance to the nearest fragment could be about 200 parsecs. These fragments could then perhaps be detected using JWST or via microlensing.

James Vesper, from New Mexico State University, studied the possibility of how free-floating planets, or rogue planets, could interact with a solar system. He performed 156 N-body simulations of encounters of rogue planets within our Milky Way, and found that 60% of the simulations resulted in a slingshot scenario, where the rogue is captured and then slung out of the system. Other possible results are the the rogue planet is captured, then leaves the system, taking a planet with it, or that the rogue planet is captured into the solar system without disturbing the orbits of other planets. From these results, Vesper found that it is possible the proposed Planet 9 could have been captured as a free-floating planet, given its orbit.

New results for direct imaging of exoplanets were given by Thayne M. Currie of Subaru Telescope and NAOJ and Tyler Groff of Princeton University. This imager uses a coronagraph and extreme adaptive optics to directly image planets orbiting closely to their host star. With this instrument, astronomers have imaged possibly the youngest debris disk ever detected. Groff described the CHARIS integral field spectrograph, which is optimized to detect planets existing extremely close to the star. Between the imager and the spectrograph, even more direct images of exoplanets are on their way.

The final presentation of the press conference was given by Carol A. Grady from Eureka Scientific. She discussed the transiting exocomets of an A star called HD 172555. Using absorption spectroscopy from the Hubble Space Telescope, she found absorption features in silicon and carbon that were visible through two different sets of spectra. These absorption signatures are similar to what is expected for sun-grazing comets if they were to have enough material associated with them. For the first time, comets in other solar systems have been detected.

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Helen B. Warner Prize: Feedback: Now with Physics (by Chris Faesi)

Title slide that MOVES. Hopkins's recent simulations were made for an IMAX film #aas229 pic.twitter.com/gvkHp0G1xF

— NicHOLTZ (@NoisyAstronomer) January 6, 2017

Philip Hopkins of Caltech won this year’s Warner Prize, which is given by the AAS to a young scientist for a “significant contribution to astronomy in the five years preceding the award.” In his prize talk, Hopkins focused on a large body of work his research group has done to investigate a series of long-standing questions in astrophysics through the use of state-of-the-art numerical simulations. His basic point: that feedback — the return of energy, momentum, and mass to the interstellar and intergalactic media from stars, supernovae, and AGN — plays a hugely important role in regulating the evolution of galaxies, and it is thus crucial to model feedback as realistically as possible in simulations.

Previous-generation simulations have revolutionized our understanding of the evolution of the universe, including how galaxies form and evolve. However, there remained a number of important observational results these simulations failed to address. For example, standard Lambda-CDM cosmology predicts the hierarchical assembly of galaxies over time, and thus the presence of a very large number of satellite galaxies for each large galaxy such as the Milky Way. We observe many, many fewer such dwarf galaxies in our local group than what is predicted by these simulations (this issue is known as the “missing satellites” problem). Simulations also show that dwarf galaxies all have a particular distribution of mass known as the NFW profile; actual dwarfs have much less of their mass in their centers than expected (the “core-cusp” problem). Perhaps most egregiously, the majority of cosmological simulations convert essentially all of their gas into stars, leading to factors of 10 to 100 too many stars and an equal overestimate of the star formation rate as compared to what we observe in galaxies today.

One of the obvious reasons for the latter issue is that simulations attempting to model large portions of the universe over billions of years simply cannot achieve the spatial resolution to properly treat the physics of star formation, which occurs on scales of tens of parsecs and smaller. These simulations use simple prescriptions, often based on observed trends such as the Kennicutt-Schmidt relation, to simply convert some fraction of gas into stars globally in galaxies. Similar approaches are needed for treating other small-scale physics such as AGN, supernovae, and chemistry. These so-called “subgrid models” save immense amounts of computational time, but also gloss over potentially important physics.

Phil Hopkins: "Nature hates theorists, it couples physics from the smallest to the largest scales" #aas229

— astrobites (@astrobites) January 6, 2017

Hopkins’s FIRE simulations focus on a single galaxy evolving from the beginning of the universe to today, and by limiting the largest scale to 100s of kiloparsecs (and through improvements in computing power and algorithms), they are able to resolve scales of less than 10 parsecs — small enough to incorporate some realistic physics of star formation and feedback. The latter is particularly important: massive stars explode as supernovae at the ends of their short lives, and these energetic events inject a huge amount of energy (as well as momentum and mass) into the surrounding medium. Furthermore, star formation occurs in clusters, not uniformly throughout a galaxy disk, and thus supernovae tend to overlap rather than be distributed at random. The overlap increases the total energy input, which can at times be high enough to push bubbles and plumes beyond the galaxy’s potential well. These processes act to limit a galaxy’s ability to form stars, as the injected energy opposes gravity’s inward force, disrupts the molecular clouds from making more stars, and in the case of supernova overlap can even strip gas from galaxies entirely. As a result, star formation is self-regulated: gas collects under gravity, stars form, supernovae explode, and then gas that may have been able to form stars no longer can. Including this feedback realistically in simulations mostly resolves the huge discrepancy between the predicted and observed star formation rates.

Phil Hopkins revisits a classic paradigm in galaxy formation: central black hole can quench star formation & explain observations #aas229 pic.twitter.com/rE1y8C3AjO

— astrobites (@astrobites) January 6, 2017

Hopkins showed that feedback also resolves the missing satellites and cusp-core issues. Since dwarf galaxies are much less massive than Milky Way-type galaxies, their gravitational potentials are much shallower. Supernovae and feedback processes from AGN are thus very effective at unbinding stars (and gas) from dwarf galaxies. This can lead to either their disruption (meaning there end up being fewer dwarfs than otherwise expected, solving the missing satellites problem), or the pushing of mass towards the outskirts of galaxies, solving the cusp-core problem. The resolution of these long-standing discrepancies between predictions of standard cosmology and observations is evidence that Lambda-CDM — with the physics of feedback included — does a really good job of explaining how galaxies evolve over cosmic time. Naturally, there are still many open questions, including the details of how feedback from AGN couples to the much, much larger scales it seems to affect, the role of magnetic fields, the nature of dark matter, and the growth of supermassive black holes. As simulations become more sophisticated and realistic, and simulators continue to innovate, perhaps these issues will soon be able to be directly addressed as well.

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Plenary Session: Astronomy from the Upper Stratosphere: Key Discoveries and New Opportunities from High Altitude Scientific Balloons (by Michael Zevin)

Earth’s atmosphere is a burden to astronomers. Even for the radiation that can penetrate through the atmosphere at all, we still have to worry about absorption and scattering. This is alleviated by building observatories at high altitudes and in dry climates. If you have really deep pockets, you could fund a space-based telescope mission, though these cost hundreds of millions to billions of dollars. Aircraft-based telescopes like Sofia can get above 90% of the atmosphere, but still cost over $300 million. However, there is a cheap and effective means to overcome the atmosphere—strap your telescope to a high altitude balloon!

Modern balloon-borne projects can get above 99.5% of the atmosphere for a fraction of the cost. This means effective scientific endeavors cost only about $10 million! Furthermore, the cheapest high-altitude balloons can cost as little as $100 per launch, providing a great opportunity for young students to test the scientific waters. Laura Fissel of NRAO spent the last plenary of the day discussing such projects in astronomy, and some of the great science that has come out of these balloon-borne projects.

The balloons used for these kinds of experiments have the consistency and thickness of a typical sandwich bag, but can lift payloads of 6000 pounds over 40 kilometers into the atmosphere. Like a balloon in a vacuum chamber, the incredibly low atmospheric pressure at these altitudes causes them to grow to the size of an entire football stadium! Antarctica is one of the best places to launch these balloons and do observations because the wind patterns allow it to circumnavigate the pole and can stay in the sky for up to 2 months.

Fissel worked with a project called BLAST (Balloon-borne Large-Aperture Sub-millimeter Telescope), a 1.8-meter telescope that had the ability to study galactic dust and star formation. The first flight took place in Antarctica in 2006. After completing its science and detaching from the balloon, the payload parachuted back to the ice below. However, once it reached the ground, the parachute failed to detach and the winds of Antarctica took the payload paraskiing across the ice for 200 kilometers, ending its long journey in an inaccessible crevasse.

Laura Fissel tells of science hardships: after landing parachute failed to detach, BLAST went peraskiing across Antarctica for 200km #aas229 pic.twitter.com/BKWsAx6Hjr

— astrobites (@astrobites) January 6, 2017

However, Fissel commented that this “could have been disastrous, but was actually the most successful BLAST flight.” Many components shook off during the telescope’s 200-kilometer journey, including all the data! In the end, BLAST made strides in understanding the contribution of high-redshift galaxies to the cosmic infrared background.

After recovering the retrievable pieces from Antarctica, Fissel and the BLAST team rebuilt the apparatus and attached a polarimeter to create the revamped BLAST-Pol. This mission, which targeted the Vela C Giant Molecular Cloud, launched in 2012 and provided an unmatched analysis of magnetic fields in molecular clouds. BLAST-Pol observed polarized light, which results from aligned dust grains due to the presence of magnetic fields. These magnetic fields can play a vital role in star formation because they act against turbulence to inhibit the formation of new stars. Fissel then looked towards the future of balloon-borne astronomy with BLAST-TNG (BLAST-The Next Generation, hats off to the Star Trek reference), which will have six times the resolution of the previous BLAST experiment. Clearly, balloon-borne experiments have much more science on the way!

Editor’s Note: This week we’re at the 229th AAS Meeting in Grapevine, TX. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting 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.

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Plenary Session: The LED Outdoor Lighting Revolution: Opportunities, Threats and Mitigation (by Ashley Villar)

Dr. Martin Aubé (Cégep de Sherbrook) kicked off the day with a keynote address focusing on light pollution and the impacts of LED lighting. Two types of light pollution affect cities and astronomers alike: direct (which is directly pointed towards the sky) and indirect (which is scattered upwards). Aubé pointed out a number of reasons why all citizens should care about these types of light pollution, including reducing our energy consumption, improving quality of life and (of course) darker night skies for astronomy. Using sophisticated numerical models and satellite images, Aubé and his team predicted that by 2025 the majority of the east coast of the USA will not be able to experience unpolluted night skies.

Additionally, the blue color of newer LED lights might have unexpected consequences. For example, blue light scatters easily in the atmosphere (which is why our sky is blue!). The additional scattering will further contribute to the growing light-pollution epidemic compared to redder lights. Additionally, blue lights have been linked to melatonin suppression and certain cancers.

But there is hope! Aubé points out a few ways to help reduce light pollution:

1. Installing motion detectors in light fixtures around the city.
2. Create sky blockades above city lights (such as trees).
3. Changing 4000K or 2700 LEDs with high pressure sodium or PC Amber LEDs.
4. Simply reducing the power of light fixtures by 50%.

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201 Plenary Session: AAS Prize Presentations: Buchalter Cosmology, Weber, George Van Biesbroeck, Tinsley, LAD Astrophysics Prize, Education (by Nathan Sanders)

AAS President Christine Jones had the special privilege this morning of conferring some of the Society’s most prestigious honors to a set of true luminaries of our field. The short ceremony was dotted with anecdotes about the recipients shared by their nominators — some colorful, and all illuminating as to the character traits that transform a long and productive career into a truly impactful one. While the full list of recipients is available on the AAS website, we’ll discuss just a few of the winners here.

Lynn Cominsky received the AAS Education Prize in recognition of the remarkable series of education and outreach programs she’s built alongside her career researching high-energy phenomena including X-ray bursts and pulsation. Her group has led the high-profile outreach efforts for a long list of NASA missions including Swift, Fermi, and NuSTAR, has founded the NASA Educator Ambassador Program. When her students built and launched a small microsatellite in 2013, Jones noted, Cominsky joined an exclusive subset of humanity that has a satellite control center in their own home.

Receiving the George Van Biesbroeck Prize for extraordinary service to astronomy, Rick Perley was recognized for contributions to both the hardware and wetware of astronomy. While playing a critical role in the design and construction of generations worth of world-leading telescopes at the National Radio Astronomy Observatory (NRAO), where he has worked for 40 years, Perley had at least as much of an impact in three decades of operating the semiannual synthesis imaging school that has taught legions of radio astronomers how to use and do science with NRAO’s instruments. Jones noted that this scientist education model has been replicated around the world.

Andrew Gould (Ohio State University) is this year’s recipient of the Beatrice M. Tinsley Prize, which rewards “an outstanding research contribution to astronomy or astrophysics, of an exceptionally creative or innovative character.” Adding to a distinguished career exploring galactic structure, dark matter, and other topics, Gould pioneered the use of microlensing as a technique to detect and characterize exoplanets. In nominating him, his colleagues described Gould as a “renaissance astronomer.”

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Thesis Talk 204.03D: Chris Faesi, Bridging the Gap from Galactic to Extragalactic (by Nathan Sanders)

Much of our understanding of how stars form in the universe comes from studies of our own Milky Way galaxy, where we can study stellar nurseries (giant molecular clouds, or GMCs) with the benefit of a constituent’s perspective. But the launch of new, more powerful interferometers like ALMA make it possible to extend these studies, and in some ways even top them, with high resolution studies of distant galaxies.

In a talk summarizing a PhD’s worth of investigations into star formation throughout our Local Group, Astrobites author Chris Faesi also shared new results from a massive campaign of CO observations with ALMA that use the nearby galaxy NGC 300 as a testbed for understanding how star formation operates across scales from individual GMCs to different types of galaxies, within and beyond the Milky Way.

While it’s been long known that galaxies with more insterstellar gas form stars at a faster rate (see the Kennicutt-Schmidt relation), earlier studies by Faesi and his advisor Charlie Lada established that individual GMCs also show a mass–star formation relation and, moreover, that these two relations seem to be part of the same continuum of star-formation processes across drastically different scales.

The resolving power of ALMA allows us to fill in the gap between these two scales, to check whether this continuum persists between Milky Way GMCs and populations of entire galaxies. Pointing ALMA at NGC 300 offers the opportunity to measure the physical properties of a much larger sample of individual GMCs with uniform sensitivity than we could collect even within the Milky Way.

Importantly, Chris’ ALMA results show that Larson’s longstanding laws for star formation in the Milky Way also extend to the much smaller spiral, NGC 300. As these empirical, observed relations are key pieces of evidence in our theory of star formation, confirming that they apply to other types of spiral galaxies points to a universal process for star formation in these galaxies.

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Press Conference: Galaxies & Black Holes Therein (by Susanna Kohler)

This morning’s press conference opened with a discussion by Niel Brandt (Pennsylvania State University) about an stunning new image released from the Chandra X-ray observatory. The image, which is officially the deepest X-ray image ever made, was built by staring at a patch of sky about 60% the size of the full moon in the sky and collecting over 7 million seconds (that’s about 11.5 solid weeks!) of Chandra observations of this region. The central region of the resulting image contains the highest concentration of black holes ever seen, which can reveal information about the growth of black holes over billions of years, beginning soon after the Big Bang. You can read more these Chandra observations in the summary of Brandt’s plenary talk below, or check out the team’s press release here.

Next up, Reinout Van Weeren (Harvard-Smithsonian Center for Astrophysics) presented yet another new image using Chandra data — this one a dynamic composite of optical, radio and X-ray radiation revealing the dramatic collision of two galaxy clusters. Van Weeren explained that the new Chandra observations link together energetic eruptions fueled by supermassive black holes and the collision between two galaxy clusters for the first time. This “cosmic double whammy” has generated a colossal shock wave that can accelerate particles to tremendous speeds. Read more in the press release here.

Ian Steer (NASA/IPAC Extragalactic Database) concluded the session with a discussion of what’s new in the NASA/IPAC Extragalactic Database (NED), an online repository containing information on over 100 million galaxies. Steer introduced us to NED-D, a special catalog that currently contains over 166,000 redshift-independent distance measurements for over 77,000 galaxies. This growing catalog will allow astronomers to make increasingly precise estimates of distances to galaxies, the scale size of the universe, the expansion rate for the universe, and even the rate of change of the universe’s expansion rate. More information can be found here.

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Plenary Session: What We Don’t Know About the Beginning of the Universe (by Joanna Bridge)

In his plenary session, Dr. Sean Carroll discussed many theories for how the universe began. What we do know about the beginning of the universe is that, as Carroll notes, “Something bang-like happened.” The universe came to be in a hot, dense state, expanding rapidly but decelerating in its expansion. Initially, the early universe had extremely low entropy. We know this because the early universe was isotropic and homogeneous, while high entropy states are rather lumpy. The curious thing about this low initial entropy is that it requires enormous “fine-tuning”. In other words, a universe that begins with low entropy is very unusual. If we add the theory of inflation of the universe on top of the Big Bang, we get a universe that begins with even lower entropy than required just by the Big Bang itself. Carroll emphasized that any theory that attempts to explain the beginning of the universe must not only account for the low entropy state of the universe but also explain why this was the case in the early universe.

Carroll went on to describe ways the universe came to be. Either there was a beginning, or else something the mimicked a beginning but was not. He described several cosmologies that would fit this bill. Bouncing cosmologies, where the universe experiences a big crunch before re-expanding, still has an entropy problem. If entropy grows monotonically through the crunch and into the subsequent expansion, then the universe is not symmetric about the bounce — talk about requiring fine-tuning! This explanation requires infinite fine-tuning.

Cyclic cosmologies are those in which the bounce occurs infinitely over and over, continually expanding then contracting. Hibernating cosmologies describe a universe that stays in a quiescent state for a long time before exploding into a Big Bang. But again, these cosmologies result in an entropy catastrophe! Any theory of the Big Bang needs to have both compatibility with low entropy early on as well as an explanation for why.

Carroll instead prefers reproducing cosmologies. Reproducing cosmologies are those in which a “parent” universe exists that is both quiescent and high entropy. Through some mechanism, it can give birth to new offspring universes, with initially low entropy. This would involve some kind of spacetime quantum tunneling to form the disconnected baby universes. These small universes would be much more likely to start off with low entropy, thereby eliminating the initial low entropy problem.

Of course, all of these theories are posited assuming a classical general relativistic universe. However, we cannot forget about quantum mechanics! Carroll described how quantum mechanics must be incorporated into these cosmologies, perhaps creating a quantum state that has infinite room to grow and change. A quantum theory for the universe must be determined to correctly describe the universe in which we currently exist.

Carroll closed with a letter he received from a 10 year old skeptic of his work who wasn’t too impressed with Carroll’s theorizing about how the universe might be put together. The P.S., in case you can’t read it, says, “Some people just have too much time.”

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Press Conference: Latest Results from the Sloan Digital Sky Survey (SDSS) (by Meredith Rawls)

Links to SDSS press releases: http://www.sdss.org/press-releases/

The Sloan Digital Sky Survey (SDSS) continues to be a remarkably successful mission. Most recently, the Apache Point Observatory Galactic Evolution Experiment (APOGEE) portion of SDSS has mapped the chemical composition of our Milky Way galaxy and discovered that the elements of life are most abundant near the center.

Karen Masters (University of Portsmouth) began the press conference by introducing SDSS and describing what is next for APOGEE. It has measured spectra for bright red giants throughout the northern sky, and now a twin of the original instrument is on its way via boat to APOGEE-2 South in Chile. It will arrive later this month and begin mapping the parts of the galaxy only visible from the southern hemisphere from Las Campanas Observatory. Jon Holtzman (New Mexico State University) then discussed how APOGEE uses infrared spectroscopy to study stellar populations and the history of our galaxy. Because elements form in stars with different timescales, a snapshot of their compositions today can tell us a lot about how the population came to be. Specifically, the key elements of life are “CHNOPS” — Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur — and their abundances vary in different parts of the Milky Way. In fact, as Sten Hasselquist (New Mexico State University) reported, all these elements are more abundant toward the center of the galaxy and less abundant farther out. He found that the elements in the inner galaxy have had billions more years to potentially develop life, saying “the longer timescale is tantalizing.”

Now that APOGEE has revealed what stars are made of, Johanna Teske (Carnegie DTM) set out to simulate the composition of exoplanets around those kinds of stars. She measures the “Earth-likeness” of these planets by simulating the process of differentiation given a set of available ingredients. If we know what a planet is made of, we can infer whether it has the potential to have an atmosphere, magnetic field, or even plate tectonics.

To close out the session, Kelly Holley-Bockelmann (Vanderbilt) presented important work being done by the entire SDSS community to improve diversity. A census of the collaboration found that it largely mirrored the astronomical community and was disproportionately white. In one effort to remedy this, the SDSS FAST (Faculty And Student Team) initiative began. The program recruits students from underrepresented groups at all levels to work with faculty and postdoc mentors on a research project funded by SDSS. Kelly reported that 57% of the FAST students are women, 66% are underrepresented minorities, and at least 25% are first generation college students. The program is going strong in its second year with six teams, and many FAST students are presenting research results at this very conference.

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Dannie Heineman Prize for Astrophysics: Increasing Accuracy and Increasing Tension in Ho (by Ashley Villar)

Dr. Wendy Freedman won this year’s Dannie Heineman Prize, a joint prize between AAS and the American Institute of Physics. Her keynote focused on the history of the Hubble constant and its measurement. She began her talk focusing on her personal history, pointing out that as a young researcher she was discouraged from studying the Hubble constant. At the time, some senior scientists believed that the Hubble constant was well understood, and had a value of 50 km/s/Mpc. Luckily, that did not stop Freedman from her now lifelong pursuit to measure this fundamental parameter.

Over the last few decades, the uncertainty on the Hubble constant has decreased from a factor of two to about 10%. However, today there is an unexplainable 3.4-sigma discrepancy between the Hubble constant measured using traditional rungs of the distance ladder and that measured using the cosmic microwave background. Freedman pointed out that these discrepancies might be yet uncovered systematic errors or something more exotic, like a new relativistic species or a modification of gravity.

Freedman hopes that by improving measurements of the Hubble constant along the distance ladder, we can uncover the source of this discrepancy. Especially important will be the future Gaia data releases, which will provide precise astrometry to measure cepheid distances. Additionally, the Carnegie Chicago Hubble Project will continue to measure the tips of the red giant branch in more distant galaxies as another rung of the distance ladder.

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HEAD Bruno Rossi Prize: A Good Hard Look at Growing Supermassive Black Holes in the Distant Universe (by Michael Zevin)

In the final plenary of the day, Niel Brandt (Penn State) took the stage after being awarded this year’s Bruno Rossi Prize for his ongoing work in X-ray astronomy. Brandt focused on active galactic nuclei (AGN) and the surveys of these objects from the Chandra X-ray observatory. High-energy emission from AGN is believed to be produced in the coronal structure of the accretion disk around supermassive black holes in distant galaxies. Though this emission originates from the galactic centers obscured by giant swaths of absorbing dust, the penetrating power of X-rays reveal these extreme objects just like an X-ray machine reveals the bones within your body.

Brandt highlighted discoveries from the Chandra Deep Field South (CDF-S) survey, which provided one of the deepest views of the X-ray sky. This survey found over 1000 X-ray sources, most of which were AGN, in a region of the sky only about ⅔ the size of the full moon. Furthermore, it stared at this region for about 7 million seconds (~81 days), allowing analysis of AGN variability and further exposing the faintest of faint sources. In fact, the faintest signals picked up by this survey were detected from only 1 photon count on the CCD every 10 days — a testament the the technological sophistication of the telescope’s camera. From the number of AGN discovered in this X-ray survey, the predicted number of AGN across the entire sky could exceed 1 billion!

This zoo of spectrally-analyzed AGN observed for extended durations has helped to solidify how these distant beasts evolve with their host galaxy, and how they relate to galactic properties like the star formation rate. Brandt concluded with a look forward to the great X-ray observatories that await astronomers in the future, such as eROSITA and Athena.

Editor’s Note: This week we’re at the 229th AAS Meeting in Grapevine, TX. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting 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.

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Welcome Address by AAS President Christine Jones (by Joanna Bridge)

American Astronomical Society President Dr. Christine Jones kicked off AAS229 by welcoming everyone to the meeting here in Grapevine, Texas.  She highlighted many advances in astronomy over the last several decades, including our better understanding of the age of the universe, the presence and magnitude of dark energy, and how we said farewell to our Solar System’s ninth planet, Pluto.  She highlighted many exciting topics to be discussed throughout this conference: the explosion of the field of exoplanet research, and marked the landmark detection of gravitational waves announced this year by the LIGO collaboration.  Additionally, advances in the fields of high redshift galaxies, black hole feedback, and star formation will be announced in the coming days, as well as some discussion of high altitude balloon missions and the effects of light pollution on the field of astronomy.

Many new telescopes and space missions are on the horizon, such as WFIRST, TMT, JWST, E-ELT, and GMT, and several sessions will be devoted to developing and using these facilities.  Planning for the Decadal Survey of 2020 is also getting underway. Finally, important discussions regarding our community will take place, such as the Town Hall on Racism = Power + Privilege, and events hosted by the Committee on the Status of Women in Astronomy (CSWA), the Committee on the Status of Minorities in Astronomy (CSMA), and the Committee for Sexual-Orientation & Gender Minorities in Astronomy (SGMA).

It sounds like AAS229 is going to be great!

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Kavli Foundation Lecture: Early Solar System Bombardment: Exploring the Echos of Planet Migration and Lost Ice Giants (by Josh Fuchs)

Dr. William Bottke (Southwest Research Institute) started by reminding everyone that we know about an amazing diversity of exoplanets due to the explosion of exoplanet discoveries over the past 20 years. However, it is very difficult to study and understand small bodies like asteroids and comets because of observational constraints, as they are very small and impossible to see around other stars. These small bodies are tantalizing, as they contain many clues to how planetary systems evolve. He compared it to a crime scene: small bodies are the bone chips and blood spatters that tell us what happened in the past.

Dr. Bottke then suggested that our solar system might have originally had another Neptune-like planet that was expelled at some point. He is trying to use some strange features in the orbits of planets and asteroids to see if an additional ancient planet may have been the culprit. An extra planet might help explain the existence of irregular satellites (comet-like objects that are found orbiting around all outer planets on highly eccentric orbits) and Trojan asteroids (asteroids in the same orbit as Jupiter, just ahead and behind in the orbit at different Lagrange points). By including this extra Neptune-like planet in dynamical models of the solar system, he can reproduce the existence of these irregular satellites and Trojan asteroids. Dr. Bottke emphasized that these are not clear evidence that our Solar System used to have another Neptune-like planet, but they are hints that we might be missing some things that happened early on in our Solar System’s history.

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Press Conference: Closing in on a Fast Radio Burst (by Meredith Rawls)

Thanks to dedicated radio observations with the Jansky Very Large Array (VLA) in New Mexico, a team of astronomers has pinpointed the source of a repeating Fast Radio Burst (FRB) for the first time. These mysterious, highly energetic transient events have been featured on Astrobites a few times, and their physical cause remains unknown. Compounding the problem, due to the nature of single-dish radio telescopes, it is difficult to determine exactly where in the sky any short-lived event is coming from. A series of papers published today changed that with an array of radio telescopes and bit of luck.

During the press conference, a packed room of reporters and scientists heard from Shami Chatterjee (Cornell University), Casey Law (UC Berkeley), Jason Hessels (ASTRON), Shriharsh P. Tendulkar (McGill University), and Sarah Burke Spolaor (NRAO). They found a faint persistent optical and radio source within 10 milliarcseconds of the FRB. The host galaxy is at a redshift of z ~ 0.2, and it’s a small, low-mass star-forming dwarf galaxy. The FRB, named FRB 121102 after its initial date of discovery by Arecibo, is the only known source to undergo multiple bursts. Thanks to this, it was possible to pinpoint its location ten times more precisely than if it had been a single event.

FRB 121102 is not located quite in the center of its dwarf galaxy home, but is instead offset by about 200 milliarcseconds, or a quarter of the host galaxy’s radius. This means it’s less likely that the source is associated with an active galactic nucleus (AGN). Based on what we know about its distance and energy, FRB 121102 must be very small—on the order of kilometers. Jason Hessels quipped that it is “probably literally smaller than this convention center.”

All of the presenters emphasized that while this is a very exciting development toward understanding FRBs, it is important to remember this detection represents a single member of the FRB population. Perhaps we stumbled across a weird one! It is too soon to draw conclusions about all FRBs based on observing just one, and doubly so given that we still have no idea what is physically causing them. Sarah Burke Spolaor said this “great new astronomical mystery has broken open a new realm of science and discovery.” Not only are FRBs inherently fascinating, but they can also serve as tools to probe the contents of the universe between us and their host galaxies.

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Annie Jump Cannon Award: The Tumultuous Lives and Deaths of Stars (by Ashley Villar)

Dr. Laura Lopez (Ohio State University) received this year’s Annie Jump Cannon Award. Her talk focused on stellar feedback, a catch-all term that describes the various ways in which stars deposit energy and momentum into the interstellar medium (ISM). Early in a star’s life, it has powerful protostellar outflows which last for less than a million years (a blink of an eye in the cosmic timescale!). Once these stars form, they continue to feed energy and momentum into the ISM. Most notably, the deaths of massive stars (a small fraction of the total star population) injects thermal energy into the surrounding ISM. Lopez highlighted the fact that feedback plays an important roles at both small (1 parsec) and large (> 10 kiloparsecs) scales, although our understanding of this complex process is plagued with systematic uncertainties. These uncertainties stem from many factors: the dynamic range of the effects, the variety of feedback mechanisms, and the lack of observational constraints.

Lopez zoomed in on a specific case, the HII region 30 Doradus, where her team has been able to observe the full SED with high spatial resolution. With this data, Lopez can calculate the radiation pressure of various regions associated with different processes. This pressure measurement quantifies the feedback processes.

To conclude, Lopez emphasized the importance of membership within our community, especially for typically underrepresented and underserved populations.

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Workshop: Introducing Current Research Into Your Classroom (by Susanna Kohler)

Ever feel like astronomy and physics classes don’t spend enough time introducing students to cutting-edge research currently being done in the field of astrophysics? This afternoon, Astrobites tackled this problem in our first-ever workshop for astronomy educators on how to integrate Astrobites into the classroom! A group of 25 educators teaching high school, undergraduate, and graduate classes gathered for an hour and a half to discuss a variety of ways that posts on astrobites.com could be used in lessons to allow students to experience recent astronomy research related to fundamental concepts taught in the course.

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Press Conference: Recent Science Breakthroughs from Arecibo Observatory (by Susanna Kohler)

The second press conference of the meeting featured four speakers who discussed the most recent results coming from Arecibo Observatory, the 305-meter radio dish built into the landscape in Puerto Rico.

Joan Schmelz (Arecibo Observatory / Universities Space Research Association) began the session by discussing Arecibo’s recent discovery of an object that affected observations of the cosmic microwave background (CMB; made by the WMAP and Planck spacecraft). The observations of small-scale structure of the CMB, which tells us about events in the early universe, can be contaminated by foreground galactic sources. Recent Arecibo observations in the Galactic Arecibo L-Band Feed Array (GALFA) HI survey reveal an unexpected foreground contributor to this signal: cold hydrogen gas associated electrons in the diffuse interstellar medium of our galaxy. This component will need to be included in future foreground masks when we attempt to better understand our observations of the CMB. Check out the full press release here.

Next up, Victoria Kaspi (McGill University) discussed an unusual pair of objects: two “part-time” pulsars discovered as part of Arecibo’s PALFA survey. Pulsars are rotating, highly magnetized neutron stars that appear to pulse as the beam of radiation from their magnetic poles rotates in and out of view like a lighthouse. Unlike the majority of the 2,500 known radio pulsars, however, PSR J1910+0517 and PSR J1929+1357 are only “on” a small fraction of the time: 30% and 0.8% of the time, respectively. These intriguing objects suggest there might be many other similar pulsars out there that we just haven’t discovered yet due to the small amount of time they spend being observable! The two pulsars also provide some additional intrigue related to how pulsars age. As pulsars grow older, they “spin down” over time as they lose energy, gradually rotating less and less rapidly. Observations of these part-time pulsars suggest that the spin-down rate is dependent on whether or not the pulsar is “on”: the pulsars spin down faster when they’re on and slower when they’re off. More information is in the press release here.

The next speaker was Tapasi Ghosh (Arecibo Observatory), who shared Arecibo’s contributions toward measuring the fine-structure constant, alpha. Alpha is a universal constant that describes the electromagnetic interaction between elementary charged particles; one practical example is that if alpha’s value were twice as large, atoms would decay twice as fast. Recent Arecibo measurements have placed constraints on the answer to an open question: is the fine-structure constant actually constant in time? Or has it changed over the years? Arecibo observations of a distant galaxy behind a foreground cloud of OH molecules allowed scientists to measure the fine-structure constant as it was at the distance of the galaxy, about 3 billion light-years away. They find that it has remained effectively unchanged: over 3 billion years, alpha has varied by no more than 1.3 parts in a million.You can read more about their research in the press release here.

Christopher Salter (NAIC / Arecibo Observatory) rounded out the session with a discussion of results from the Arecibo-RadioAstron VLBI Active Galactic Nuclei Survey. This project links the Arecibo Observatory with the Russian RadioAstron satellite to simulate a radio dish of up to 350,000 km in diameter, able to make observations at unprecedented detail of the nuclei in distant active galaxies. Among the survey’s recent outcomes are new measurements of the nucleus of 3C 273, famed for being first quasar discovered. The project found that 3C 273 has a brightness temperature that is significantly higher than the maximum allowed by current models of how quasars shine, challenging our understanding of the physics at work in the vicinity of supermassive black holes. You can read more about their observations in their press release here.

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Henry Norris Russell Lectureship: How Stars Form (by Michael Zevin)

In the last plenary talk of the day, aptly named “How Stars Form”, Christopher McKee (University of California Berkeley) discussed many of the open questions in star formation. Though the basics of star formation is a topic everyone learns from their first astronomy class, the intricacies underlying stellar population models, the effect of stellar environments on star formation, and the ability to generate particular kinds of stars are still embedded with uncertainties. The topics that McKee touched on are:

1. Stellar mass similarities in differing environments. The density of stars that reside in the galactic “field” differs by orders of magnitude compared to populations in globular clusters, yet the typical mass of a given star is unexpectedly similar.
2. The initial mass function (IMF). This is an empirical function that describes the mass distribution of stars (i.e. how many stars of one mass there are compared to stars of another mass). From observations it appears to be nearly universal, however certain environments such as young star clusters and elliptical galaxies appear to have unexplained deviations.
3. Star formation rate (SFR). The Kennicut-Schmidt relation, empirically formulated in 1959, proposed that the star formation rate per unit area is proportional to the gas surface density raised to some power. However, more recent findings may indicate that the star formation rate is instead proportional to the molecular gas surface density rather than the total gas surface density.
4. Massive stars. We see them, we know they exist. But we still don’t know exactly how they form. Stars over 20 solar masses have enormous radiation pressure — so much so that hydrostatic equilibrium may not be maintained. McKee suggests that this radiation pressure problem may be reconciled with the help of Rayleigh-Taylor instabilities.
5. Magnetic fields. Magnetism throws a twist on everything astrophysical, and the role of magnetic fields on star formation is still up in the air. Observations of the mass-to-magnetic flux ratio (in a sense, the importance of gravitation over magnetism) may be hinting that magnetic fields play less of a role in star formation than previously thought.
6. The first stars. These stars are thought to form dark matter mini halos in the early universe that were on the order of a million solar masses. Simulations show this formation process and the lack of metals at these early times preferentially churns out massive stars. However, this is true specifically for the cold dark matter model, which is the most accepted model for dark matter. Through what McKee calls “cosmic archeology”, we may soon be able to analyze such stars to gain further insight into the nature of dark matter itself.

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Town Hall: Racism = Prejudice + Power: A Discussion of Racism in the Field of Astronomy (by Joanna Bridge)

This Town Hall, aptly entitled in equation form as Racism = Prejudice + Power, was a panel and discussion session held to address the systemic issues of racism in our society, and in the astronomy community. The session began with an introduction by Dr. Adam Burgasser, who specifically acknowledged that the conference we are at was held on land belonging to several indigenous groups and tribes.  We were then introduced to the facilitators of the discussion, Dr. Jorge Moreno and Nicole Cabrera Salazar.

Moreno introduced us to the Town Hall Axiom, that “we hold these truths to be self-evident that all people are created equal.” He emphasized the fact that people of color are massively underrepresented in the top 40 astronomy institutions in the US, with 90.7% white, 7.1% Asian, 1.2% Latinx, 1% Black, and 0% Native American. He also quoted several statistics about the incarceration of people of color, indicating the underlying racism in society that singles out particularly Black and Latinx people disproportionately. Moreno emphasized that centuries of oppression are at the root of this racism, setting the stage for the following discussion.

Is Astronomy an affirmative action program for white people? Have a look at the data. #aas229 pic.twitter.com/13wSg1Icfi

— David Charbonneau (@ExoCharbonneau) January 4, 2017

We were then presented with guidelines for discussing difficult issues such as racism and equality.

Ground rules for AAS racism town hall. #aas229 pic.twitter.com/WWE3qrmBtc — Jackie Monkiewicz (@jmonkiew) January 4, 2017

We then broke into small groups of three to four people to discuss three specific terms and what they bring to mind: race, social power, and racism. Afterwards, we reconvened, with many people sharing their thoughts and insights on these topics.

Feeling uncomfortable discussing racism with colleagues is trivial compared to experiencing racism from your colleagues @browndwarfs #aas229

— Meredith Rawls (@merrdiff) January 4, 2017

A lesson I’ve been trying to teach my kids, but which many adults don’t get. Intent is irrelevant. The impact of your actions matter #aas229 — Karen Masters (@KarenLMasters) January 4, 2017

Recognize and check your privilege #aas229 — Jessica A. Kenney (@Jessica_AKenney) January 4, 2017

Cabrera Salazar closed the Town Hall with some parting thoughts, quoting from a song from Solange Knowles’ most recent album, “Where do we go from here?” Our job, she notes, is to educate ourselves. Great work has been done on the topics of racism and equality, by people such as Audre Lorde, Patricia Hill Collins, Eduardo Bonilla-Silva, Lydia Brown, Kimberlé Crenshaw, and Maria Yellow Horse Brave Heart.

Want to fight racism? Check out the work of these folks. Start educating yourself. #aas229 #racismTownHall pic.twitter.com/nMbaIZWwOe — Jessica Kirkpatrick (@berkeleyjess) January 4, 2017

It is also not the job of people of color to bear the brunt of the burden of fighting racism. White people should be doing the legwork because that is where the power lies.  Moreno gave the example that in the same way that men should be fighting issues of sexual harassment of women, so should white people be the ones to fight racism in our community. Listen to people who do not lie on axes of privilege. Magnify the voices of people of color. Cabrera Salazar enjoined us to do this work, every day, because that is what it takes to defeat racism.

Greetings from the 229th American Astronomical Society meeting in Grapevine, Texas! This week, along with several fellow authors from Astrobites, I will be writing updates on selected events at the meeting and posting at the end of 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 an educator who will be at the meeting and you’d like to learn how to use digests like AAS Nova or Astrobites to bring current astronomical research into your classroom, you can still register on-site for Astrobites’ workshop on the subject, “Introducing Current Research Into Your Classroom“, which will run Wednesday, 12:30–2:00 pm in Appaloosa 1.

Otherwise, we hope to see you around at Grapevine! Drop by and visit AAS, AAS Journals, and Astrobites at our joint booth in the Exhibit Hall (Booth #317) to learn more about AAS’s new publishing endeavors, pick up some Astrobites swag, or grab a badge pin to represent your AAS journals corridor!