Editor’s Note: This week we’re at the 230th AAS Meeting in Austin, TX. Along with author Benny Tsang 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. The usual posting schedule for AAS Nova will resume next week.

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Plenary Session: Space Weather: Linking Stellar Explosions to the Human Endeavor (by Benny Tsang)

Our morning speaker Delores Knipp was an Air Force officer and meteorologist, and she is currently a space weather scientist in the Aerospace Engineering Sciences Department of the University of Colorado. Space weather refers to the effects of the Sun (stellar physics) on the space environment (aerospace engineering) and on Earth’s upper atmosphere (meteorology) — and consequently on our society and technology (navigational instruments and spacecraft operations). Knipp’s broad background is not only extraordinary but is also necessary for the multidisciplinary nature of space weather.

The main causes for space weather are the energetic particles, radiation, and ejecta from stars and stellar explosions. Energy from space is vital to our well-being when it comes in mild and controlled doses, like the warm morning sunlight. However, out in space without the protective magnetic field of the Earth, a single energetic cosmic ray could destroy an instrument onboard an aircraft or damage the cells in a human body.

We can introduce redundancy (multiple copies of the same instruments) on airplanes and spaceships to ensure more reliable operations. However, for more long-duration interplanetary travels, we have to first understand the hostile environments out there. Moreover, flares and ejecta from low-mass stars have crucial implications for the habitability of planets outside our solar system. As an explorative species, space weather holds the key to our future (and gives us spectacular aurorae too!)

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Plenary Session: AAS Education Prize: Growth of Astronomy Education in Chile: A Late But Successful Story (by Benny Tsang)

This plenary talk was unlike any other talks I attended in academic meetings; it felt like a superhero movie. Hernán Quintana (Pontificia Universidad Catolica) is the winner of this year’s AAS Education Prize for his devotion and accomplishment in bringing upper education and astronomy into Chile. We are all used to seeing superheroes meandering through impossible circumstances and somehow saving millions. Quintana is not far from that.

Astronomers are no strangers to Chile; this country is the key attractor of the largest astronomical investments in the world. The Very Large Telescope (VLT), Atacama Large Millimeter/submillimeter Array (ALMA), and the next-generation Extremely Large Telescope (ELT) all call Chile home. The high-quality sky conditions make Chile a wonderland for astronomy. However, due to many historical and internal barriers, development of astronomy in Chile had been slow.

Quintana built astronomy in Chile from almost nothing. An old policy in Chile required that admissions to astronomy BA and Master’s programs be limited by the number of future positions. As silly as it sounds, this policy took growth entirely out of the question. Budget reductions and economic crises in the 1980s further hindered plans for higher education in general. But by slowly building a growth mindset in the government and universities, gathering resources in every imaginable way, and initiating international collaborations, Chile has now become one of the fastest growing astronomy communities in the world.

International collaborations with France, China, and Germany are all active projects researchers should keep an eye on. Thanks to Quintana there are even new endeavors in Chile beyond astronomy, including the development of detectors, mm-wavelength technology, and weather models for planning of observations. In the years to come, Chile is going to need ~300 astronomers to make good use of the new large telescopes!

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AAS Hack Day (by Benny Tsang)

This AAS Hack Together Day was a fun one! From 9:30 am to 3:00 pm, astronomers brainstormed and conquered their hack projects. Here’s a rundown on what they have accomplished. Given the amount of time they had, their work is truly impressive.

 

 

 

 

Michael Gully-Santiago (NASA Exoplanet/Kepler) and Jena Whitley (UT Arlington) developed a learner-friendly pathfinder Python tutorial for future K2 (Kepler) and Astropy tutorials. Also thanks Gully for walking me through some cool Python packages for data visualizations — they will come in handy for my own research!

The UT Austin team of Briana Indahl, Yao-Lun Yang, and Sam Factor put together an automatic spectral fitting routine for emission lines from galaxies.

Rachael Livermore (UT Austin), Ashley Pagnotta (AMNH), and Jeffrey Silverman (SambaTV) coded and sewed a clothing-ready LED set that shined like observed supernovae!

Achievement unlocked: we've successfully programmed a sewable LED to fade in and out!! #hackaas #aas230 pic.twitter.com/mbBjawxbKM

— Rachael Livermore (@rhaegal) June 8, 2017

Lastly, the Arizona State University team Patrick Young and Karen Knierman’s created a supernova pocket square (Thanks Rachael for providing the gorgeous images and fabrics)!

Kelle Cruz (CUNY Hunter College & AMNH) is to thank for organizing and coordinating the hack day event. It is in events like these that new ideas and collaborations take shape.

See you at the next AAS meeting in Washington, DC. It’s my pleasure blogging with y’all!

Editor’s Note: This week we’re at the 230th AAS Meeting in Austin, TX. Along with author Benny Tsang 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. The usual posting schedule for AAS Nova will resume next week.

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Plenary Session: George Ellery Hale Prize, The Solar Magnetic Field: From Complexity to Simplicity (and Back) (by Benny Tsang)

The morning plenary session started with the George Ellery Hale Prize presentation of our speaker Manfred Schüssler (Max Planck Institute for Solar System Research) for his “outstanding contributions over an extended period of time to the field of solar astronomy”. Eugene Parker, who first discovered the magnetism and polarity of sunspots and who we named NASA’s new Sun-touching spacecraft after, was the first scientist to have received this honor. Today Schüssler led us on a journey to disentangle the Sun’s complex magnetic field with simple models — can this really be done?

To get a sense of the level of complexity in the magnetic structures of the Sun, let’s first take a look at some images. On the seemingly simple and boring surface, we see tiny features around sunspots (middle panel) and granules (hot, rising pockets of gas; right panel). In addition, all these are highly turbulent and dynamical, so we are faced with the challenge of explaining a hierarchy of time-varying complexities on a wide range of scales.

Numerical simulations have tried to reproduce the observed features by including physics at different scales — from the near-surface layer, to the deeper layer where the magnetic field is believed to be created, to the whole convection zone. Although simulations are not perfect in reproducing all features, Schüssler stressed that they offer an otherwise unavailable 3D view of the Sun, which allows new questions to be asked. Among all, the small-scale dynamo model shows the most promising prospects for explaining most of the observed small-scale structures. This dynamo process is so fundamental that it is believed to prevail even when the first generation of stars were born.

The Sun can be quite predictable in its own way. The highly regular, 11-year cycle of sunspot activity and the 22-year field direction reversal are two examples. Such regularities can be understood by the Babcock and Leighton (BL) model pretty well, which describes the activities as driven by the twisting of magnetic field lines in the Sun by its rotation. That said, the full picture of Solar magnetism is still far from being complete. As an example, Schüssler noted that the emergence of magnetic field deeper in the Sun (flux emergence) assumed in the BL model seems to be extremely complex in and of itself. Future scientists, I think we could really use some help here.

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Press Conference: Bending & Blending (by Benny Tsang)

The last press conference of this AAS meeting featured two speakers and had a rather enigmatic title: Bending and Blending. To summarize in one sentence, it was about the bending of light by a white dwarf, and the blending of a suite of versatile tools for better data visualization.

The impossible hope now possible: determining a white dwarf star's mass with gravity https://t.co/0n6ABX4402 #AAS230 @sciencemagazine pic.twitter.com/Ag1MLoPaHJ

— Science Press Pkg (@scipak) June 7, 2017

Kailash Sahu (Space Telescope Science Institute) led the discussion of a truly exceptional microlensing event. One of the crucial tests of Einstein’s theory of general relativity is the bending of light around massive objects. Unlike typical gravitational lensing by clusters of galaxies, microlensing events are caused by objects with stellar or planetary masses. Sahu’s team observed a foreground white dwarf (Stein 2051 B) deflecting light of a background star. By analysing the images formed by this “white dwarf lens”, they estimated its mass to be 0.675 times the mass of the Sun (with ~7% error). Until this discovery, all mass estimates of white dwarfs have relied on binary systems. Sahu’s discovery opened up a new way to measure white dwarfs’ masses, which could empower many new discoveries in astronomy. [Full press release]

Aside: If you wish to do your personal gravitational lensing observation, there’s a chance during the upcoming total Solar eclipse event on Aug 21. We can all be part of it!

Next, Brian Kent (National Radio Astronomy Observatory) illustrated the multi-purpose, well-documented, scientific data visualization tool he built, known as Blender. Data from multi-wavelength observations and advanced supercomputer simulations have been growing in both size and complexity. Not only is visualization required to help communicate new discoveries to the general public, but scientists themselves rely heavily on efficient visualization tools to make discoveries in the first place. Recently Kent has even combined Blender with Google Spatial Media to “put data in the hands of the audience” — data visualization on users’ mobile devices. We can start making our own scientific art pieces now by following the tutorials and reading the new Blender book! [Full press release]

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Plenary Session: CANDELS: A Cosmic Quest for Distant Galaxies Offering Live Views of Galaxy Evolution (by Benny Tsang) 

Inventor of photometric redshift measurement David Koo (University of California, Santa Cruz) told the story of the cosmic quest to understand galaxy formation. Having recently retired to “finally do research full-time”, Koo started by clarifying a common question about the CANDELS program — the name ‘CANDELS’ is indeed an intentional misspelling to avoid generic results on search engines. CANDELS is a Hubble Space Telescope legacy survey with an unprecedented amount of data, providing both wide and deep coverage of galaxies. The entire image database consists of 250,000 galaxies from redshift of 1.5 to 8.

Why do we want to get yet more data on distant galaxies? It is obvious from a quick glance at the Hubble Deep Field that cosmic environments vary a lot — we see galaxies of different shapes and colors! Moreover, galaxies cannot be neatly divided into discrete types; they interact with each other and evolve. A large amount of data is therefore needed to cover a representative volume of the Universe in order for a galaxy evolution study to make sense.

With complementary coverage by Herschel and Spitzer (infrared), Chandra (X-ray), and GALEX (ultraviolet), we earn the bread and butter for galaxy evolution, e.g. stellar mass, size, star formation rate, and morphology. In particular, the addition of the X-ray band provides important hints about galaxies’ central supermassive black holes. An important component of the CANDELS program is the inclusion of theorists working with N-body and hydrodynamical simulations. By reproducing observed galaxies from first principles, simulations allow us to track them back in time (like rewinding a movie) to see the processes of their evolution.

Throughout the talk Koo filled the entire hall with his warmth, and he didn’t hesitate to give thanks to his team. Besides the principal investigators Sandra Faber (who has won the Bruce Gold Medal, the “cosmology Nobel prize”) and Henry Ferguson, he also thanked astronaut Andrew Feustel for installing the camera that made CANDELS possible! With the prospects of new telescopes such as JWST, ALMA, SKA, and those of decades to come, Koo echoed Casey on Day 1, envisioning that detailed mapping of gas and dust is the future of astronomical observations.

Editor’s Note: This week we’re at the 230th AAS Meeting in Austin, TX. Along with author Benny Tsang from Astrobites, I will be writing updates on selected events at the meeting and posting each day. Follow along here or at astrobites.com. The usual posting schedule for AAS Nova will resume next week.

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Press Conference: Inconstant Stars (by Benny Tsang)

Our morning press conference featured four new studies on variable stars, ones that don’t shine steadily. The first presentation was by Rodolfo Montez from the Smithsonian Astrophysical Observatory, who spoke about a symbiotic system (a variable binary star system with a red giant transferring mass to a white dwarf) called R Aquarii. The key discovery is a large-scale X-ray jet structure on the northern side of the system, as revealed by the Chandra telescope. This discovery helps us piece together a more complete historical record of the jet ejection, crucial for understanding the connection between jets and binary orbits. [Full press release]

Thomas Kirkman (St. John’s University) then shared a puzzling result he found with his group of undergraduate researchers. Their target of observation was an eclipsing Cepheid variable in the Milky Way (TYC 1031 1262 1). A Cepheid variable is a pulsating star that changes in brightness as it expands and contracts. When Cepheid variables are in binary systems, variability due to pulsation is complicated by eclipses by the dim star, adding another level of modulation in brightness (see the light curve in the figure). Kirkman and his group found that the binary system exhibited a decreasing period (took longer and longer to go around), whereas previous observers had found an increasing trend. These results suggest a puzzling oscillation in the orbital period — something that definitely calls for more follow-up!

The next remarkable discovery was a pre-cataclysmic variable with the shortest period found to date (WD 1202-024), reported by Lorne Nelson from Bishop’s University. The variable brightness can be modeled very well as a white dwarf with a brown dwarf companion. Since only about 1% of white dwarfs have brown dwarfs as companions, this is indeed a rare find. The lack of mass transfer (what causes cataclysmic variables to vary in brightness) signatures is the reason that we call it a “pre-cataclysmic” source. It is speculated the binary orbit will shrink in size by emitting gravitational waves and become a real cataclysmic variable. But we may have to wait for ~250 million years before it happens.

GALEX (the Galaxy Evolution Explorer) is an all-sky surveying spacecraft built to observe the night sky in ultraviolet wavelengths, which can distinguish photons arriving 0.005 second apart! Its high sensitivity allows short-timescale brightness variations to be detected from low-mass cool stars. Chase Million (Million Concepts) has built a brand-new data analysis pipeline engineered to search GALEX data for flares from cool stars. It turns out that many of these flares, both big and small, were found. Habitable planets lie closer to cooler stars, so the energy from the flares might impinge on these planets’ surfaces. The discovery of the many flares in the GALEX data therefore has critical implications for the general habitability of other worlds. [Full press release]

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Plenary Session: Our Future in Space (by Susanna Kohler)

This afternoon, Chris Impey of University of Arizona gave a fiery overview of the history of space exploration, where we stand now, and where we’re headed in the future. Impey opened with a summary of the alleged first space-travel attempt in 1550: a Chinese official attempted to travel to the Moon in a wicker chair with 47 rockets attached. Unsurprisingly, it didn’t end well. Though this story is almost certainly a fictional account, the same message came through again and again as Impey walked us through the space travel history of the 20th century: going to space is hard, astronaut mortality rates are high (3–4%), and we’re well aware of the challenges. Nevertheless, we continue to find this an endeavor worth tackling.

Current prospects in the U.S. are looking progressively bleaker for government-driven space exploration. Past programs — like the Space Shuttle — are disappearing, and the budget for new programs is shrinking. The cost of space missions suddenly seems much more manageable when you change perspective, however: Impey made the unexpected comparison of space-mission costs relative to the production budget for major movies. Guess which one is, on average, larger today?

Impey: Producing the median movie costs more than the median space mission now! #aas230 pic.twitter.com/DEkLcvXTtD

— AAS Nova (@AASNova) June 6, 2017

So if you can front the money for a movie about going to space, why not instead front the money for the actual mission to space? This is the thinking behind the new private-sector-driven era of space exploration.

Major companies like Space X and Blue Origin are putting themselves on the map, and programs like Google’s Lunar XPRIZE have encouraged an expanding field of players. Commercial space travel is becoming ever more prevalent; a total of 7 space tourists have gone up to spend a vacation at the ISS, for instance, paying millions of dollars for the privilege. And roughly two years ago marked the first time in our history that the majority of space launches to low-Earth orbit were commercial — a significant milestone.

So what does the future hold? Impey believes that space exploration will continue to be driven primarily by the private sector. Some of his rapid-fire predictions for the future include successful asteroid mining endeavors, development of a permanent Mars colony, tourism to Europa, and exploration of Alpha Centauri. As for whether or not these things will actually come to pass — we’ll just have to wait and see.

You can find out more about Impey in this interview by Amber Hornsby.

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Press Conference: Galaxies, Clusters & Voids (by Susanna Kohler)

This afternoon’s press conference launched with a presentation by Jason Chu (University of Hawaii Institute for Astronomy) on a peculiar breed of galaxies: Luminous Infrared Galaxies, or LIRGs. LIRGs are extremely bright, emitting hundreds of billions or even trillions of solar luminosities in primarily infrared wavelengths. Many are interacting or merging galaxies — and as such, they’re much more common in the early universe (when galaxies were more likely to run into each other since the universe was smaller). Nearby LIRGs, however, offer a useful opportunity to study what’s happening in these galaxies in detail. Chu presented a series of far-infrared observations from Herschel mapping the 200 brightest LIRGs in the nearby universe as part of the Great Observatory All-sky LIRG Survey (GOALs). The observations of the GOALS sources are publicly available, and scientists can use the data to explore properties of these galaxies that were previously impossible to measure. [Full press release] [Original article]

Local LIRGs may be great for detailed viewing — but are we resigned to seeing more distant, early-universe LIRGs as merely fuzzy blobs? Not at all! James Lowenthal (Smith College) next told us about how Hubble is being used to explore the brightest infrared/submillimeter galaxies in the universe. Lowenthal and collaborators are in the process of obtaining stunning Hubble images (is there really any other kind of Hubble image?) of distant LIRGs that have been gravitationally lensed by foreground galaxies. He even showed us the most recent, never-before-seen image that came in during this meeting! By modeling the distorted images of the background LIRGs, scientists hope to unscramble the true shape and nature of these distant, bright, star-forming galaxies. Bonus thought for the day: Lowenthal pointed out that all distant galaxies are probably gravitationally lensed to some extent — not just the ones where the effects are obvious (like Einstein rings). “We’re looking at the universe through sheets of wiggly glass.” [Full release here]

Next up, Jack Burns (University of Colorado Boulder) discussed “banging” galaxy clusters. In particular, he presented observations of a specific cluster: Abell 115, located 2.4 billion light-years away. Abell 115 is actually a violent early-stage collision of two subclusters, each containing hundreds of galaxies. New X-ray temperature maps of Abell 115 reveal a region of incredibly hot (170 million Kelvin) gas in the center between the merging subclusters. Burns suggests that the turbulence of this extreme region may be responsible for the temperature, as the energy of the merging cluster motion is converted into thermal energy by the mixing actions of turbulence. [Full release here]

The final presentation of today’s press conference was given by Benjamin Hoscheit (University of Wisconsin, Madison). Hoscheit opened with an intriguing question: do we live in a large local void? Voids are regions of the universe that have lower densities of galaxies, stars, and planets than the average. Some past studies have found observational evidence supporting the view that we are surrounded by a large local void, and Hoscheit presented an interesting consequence of this picture if true: this could explain the tension between different measurements of the Hubble constant, the value that describes the rate at which the universe is expanding. Measurements made using the distance ladder (i.e., local measurements) estimate a value of the Hubble constant significantly higher than that measured using CMB anisotropies (i.e., cosmic measurements). If we indeed live in a local void, this would distort the pull on matter in the local area, explaining why the local estimate of the Hubble constant  is so low. [Full release here]

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Plenary Session: Planet Nine from Outer Space (by Benny Tsang)

Ever since Galileo pointed the telescope to the sky and found the phases of Venus and the four satellites around Jupiter (and many more ground-breaking observations), we have been fascinated by the discoveries of celestial objects around us. By making a strong case for the existence of the yet-to-be-discovered Planet 9, Konstantin Batygin (Caltech) shared his efforts to “make our solar system great again”.

The story started with the discovery of the Kuiper belt, a swarm of rocks going around the Sun beyond the orbit of Neptune. Most of these asteroids’ orbits can be understood with the eight planets we already have. However, when it comes to the bodies with periods longer than 4,000 years, their orbits are absurd — these long orbits seem to cluster together in space (the purple orbits in the figure), which is statistically extremely unlikely to occur by chance.

It gets more and more intriguing as we have discovered more and more anomalies in our solar system.

1. Sedna (2003 VB12) and Biden (2012 VP113) are two Kuiper belt objects with large orbits that never get too close to Neptune. Traditional theories on the early evolution of our solar system can’t explain the existence of such objects.
2. Kuiper belt objects have been discovered with orbits nearly perpendicular to typical planets. This also can’t be explained by our eight-planet solar system.
3. A mysterious object called Niku was found to orbit the Sun with a retrograde (moving opposite to nearly everything else in the Solar system), near-circular, and extremely tilted orbit.
4. The Sun’s rotational axis was found to have a 6° misalignment with the global orbital axis of the eight known major planets.

Back in October, my former student Gongjie Li and I made a wager. She bet P9-KBO dynamics is strictly secular, I bet resonant. Answer soon. pic.twitter.com/DEYi4B1yZk

— Konstantin Batygin (@kbatygin) January 9, 2017

All these “small enough to ignore, big enough to be relevant” anomalies could be explained by adding a planet with ~10 Earth masses in an orbit of ~500 AU — Planet 9! Using numerical simulations, Konstantin has successfully reproduced every single one of these anomalies. Whether we will find Planet 9 is still up in the air (in space I mean), but Konstantin’s remarkable discoveries have already made the Solar System great if you ask me! Konstantin is also a rockstar; don’t forget to check out his interview with Amber Hornsby.

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Plenary Session: Flows and Flares Around the Nearest Supermassive Black Hole — Sgr A* (by Susanna Kohler)

Did you know that our galaxy likely once hosted an active galactic nucleus? The Milky Way’s central supermassive black hole, the four-million-solar-mass Sgr A*, is much quieter today — but it still exhibits a little bit of action. Daniel Wang (University of Massachusetts) took the last plenary session of the day as an opportunity to catch us all up on some of the activity around the central black hole in our galaxy.

Why do we care about Sgr A*? Besides the intrigue of learning about our local environment, Sgr A* has the benefit of being observable. While the nuclei of other galaxies may be only a few pixels in our observations, we’re able to observe the central region of our galaxy on a broad range of scales. On arcminute scales, we can see the central star cluster and colliding stellar winds. Zooming in to a few arcseconds we can see the actual motion of stars as they orbit Sgr A*. And in the future, we hope to even get down to scales where we can resolve the shadow of the black hole itself, using effectively an Earth-sized telescope called the Event Horizon Telescope. What we learn about the center of the Milky Way by studying the region around Sgr A*, we can hopefully apply to understand the nuclei of more distant galaxies.

Over the span of his talk, Wang introduced us to a number of studies of activity near Sgr A* — including both flares and quiescent emission. The bulk of Sgr A*’s quiescent emission comes from the outer regions around the black hole (i.e., 10,000–100,000 Schwarzschild radii away); this is in contrast to active galactic nuclei, in which the innermost regions dominate the emission. Interestingly, the outflow from Sgr A* very nearly balances the inflow, with less than 1% of the accreting matter actually falling into the black hole.

Sgr A*’s activity becomes even more interesting when we look at its flaring behavior. We’ve observed about 100 X-ray flares total (mostly with Chandra, XMM-Newton, Swift, and NuSTAR), and we estimate that Sgr A* probably flares at a rate of about two times per day. These flares typically last only about an hour in X-rays. What causes them? Wang presents two possibilities: the more mundane solution of magnetic reconnection (as is the case with solar flares), and the sexier alternative of tidal disruption of asteroids. The latter model fits the data slightly better in terms of the flare distributions and their durations, but the emission models haven’t been developed enough to say anything with certainty yet.

Wang: What generates the flares? Possibly magnetic reconnection. More exciting option: tidal disruption of asteroids! #aas230 pic.twitter.com/wMIBZhGXbr

— AAS Nova (@AASNova) June 6, 2017

To conclude, Wang walks through the big picture of the life cycle of galactic nuclear activity, which begins with cold gas accretion. This leads to star formation and resulting strong hot cluster winds, which then blow out the remaining cold gas and turn off accretion. When the winds weaken, the cycle can begin anew. This cycle is regularly interrupted by disruptions of passing asteroids, planets, stars, or dense clouds.

You can read more about Wang in this interview by Chris Faesi.

Editor’s Note: This week we’re at the 230th AAS Meeting in Austin, TX. Along with author Benny Tsang from Astrobites, I will be writing updates on selected events at the meeting and posting each day. Follow along here or at astrobites.com. The usual posting schedule for AAS Nova will resume next week.

Undergrad Reception

We were excited to be able to talk to so many undergrads at the undergrad orientation and reception on Sunday night! It was great to hear about your research projects, your goals for the future, and the things you’re passionate about. Keep on being awesome, remember that we want to hear from you about your research, and let us know if there’s anything we can do to help make your entry and progression through the field of astronomy easier.

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Plenary Session: Dark Matter in the Universe (by Benny Tsang)

Prof. Katherine Freese from the University of Michigan kicked off the first plenary talk by summarizing the variety of evidence for dark matter: flat rotation curves of galaxies, signatures on the cosmic microwave background, and beautiful arcs of light around galaxy clusters via gravitational lensing, to name a few (there are a lot more!). We know dark matter is there, but how do we go about detecting it?

One of the prompt candidates for dark matter are Weakly Interacting Massive Particles (WIMPs). The three main ways to search for them are by:

1. Production method: smashing super-energetic particles together and hoping that WIMPs come out, e.g. in particle accelerators;
2. Direct method: building detectors that WIMPs directly interact with (although weakly);
3. Indirect method: indirectly seeing particles and photons produced when WIMPs annihilate (merge and give off energy).

Conventional detection methods, both direct and indirect, do not provide directional information, so we see signals but have no idea which directions the WIMPs come from. Freese mentioned a fascinating new way to detect WIMPs and their direction of travel using DNA! The basic detector unit consists of a sheet of gold atoms (their big nuclei make them better targets for WIMPs, resulting in easier detection!) with strands of DNA hanging from it, like a bead curtain. All the DNA strands have specific labels at the end but are otherwise identical. When energetic WIMPs come in, they may kick some of the gold nuclei out of the sheet, and on their way strands of DNA are cut. By collecting and looking at the strands that fall out, we can figure out the directions in which the WIMPs traveled. It’s a beautiful cross-breeding between biology and astrophysics!

Freese also discussed the possibility of seeing signatures of dark matter from an exotic kind of stars called Dark Stars. They are among the first generation of stars postulated to be powered not by nuclear fusion, but by the annihilation of dark matter particles in the cores. They are believed to be as massive as 10 million suns and as bright as a billion suns. We may be able to see them with the upcoming James Webb Space Telescope!

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Press Conference: Black Holes (by Susanna Kohler)

The first press conference of the meeting today launched with a presentation by Richard O’Shaughnessy (Rochester Institute of Technology) on what we can learn about supernova physics from gravitational waves. Black hole mergers have become one of the hottest topics in astrophysics at present, thanks to the recent LIGO detections of gravitational waves from three different merging binaries (four, if you count the trigger LVT151012!). In one of these mergers, GW151226, the black holes were smaller, enabling LIGO to detect many more orbits of the binary before the two black holes eventually merged. This revealed intriguing details — like the fact that the binary’s orbit is tilted. O’Shaughnessy and collaborators modeled how this binary might have originally formed, finding that the misalignment of the binary could be explained by the black holes’ births: if the stellar explosion that formed one of the black holes gave it a bit of a kick in the process, that could explain LIGO’s observation that the binary is tilted. You can check out the full press release here.

Next up, Stephanie Juneau (National Optical Astronomy Observatory) discussed supermassive black holes that are shrouded by gas and dust. Even if obscuration hides the black holes, we may be able to see the powerful winds emitted by these giants as they expel material surrounding them. Juneau discussed recent optical observations of the nearby galaxy NGC 7582 by the instrument MUSE on the Very Large Telescope (seen in the cover image at the top of the post). These observations reveal a ring of gas and dust 2,000 light-years in diameter that protects the galaxy from the destructive effects of the wind emitted by the hidden central supermassive black hole. The ring also may serve to focus the wind from the black hole into a more collimated flow. You can read more about these discoveries in the press release here.

Chris Shrader (NASA Goddard Space Flight Center) spoke next about the winds launched from accretion disks surrounding black holes. What drives these winds? The common theory is generally magnetic fields (it’s always magnetic fields, right?). Shrader reported on Chandra observations of the transient X-ray source GRO J1655–40, which went into outburst in 2005. The X-ray spectrum of this source can be well fit by a magnetohydrodynamic model of a black-hole accretion disk, strongly supporting the picture of magnetically driven outflows from these disks.

Lastly, Ethan Vishniac (Johns Hopkins University and the American Astronomical Society) followed up on Shrader’s presentation by discussing how magnetic fields might move around in black-hole accretion disks. The disks suck in fields from the surrounding universe (along with the gas feeding the disk), but turbulence within the disk is then expected to mix everything up. How does an ordered field result from this mess? Vishniac and collaborators’ work suggests that the primary effect at work is buoyancy. As the magnetic fields are compressed and stretched by turbulence, gas is squeezed out of the compressed regions. These sections then become lighter without the weight of the gas dragging them down, which causes them to rise. This buoyancy is what drives the motions of the magnetic fields within accretion disks.

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Annie Jump Cannon Award: Origins of Inner Solar Systems (by Susanna Kohler)

This year’s winner of the Annie Jump Cannon award is Rebekah Dawson of Penn State University, “for her work modeling the dynamical interactions of exoplanets in multiplanet systems.” Dawson spoke today about what inner solar systems — i.e., regions of planetary systems closer to their star than Earth is to the Sun — can tell us about how planetary systems form and evolve.

Cannon Prize lecturer @bekkidawson at #aas230 on inner solar systems – just about every known exoplanetary system is one. #PlanetParty!

— Charles Liu (@chuckliu) June 5, 2017

In particular, Dawson discussed what we can learn about the formation of different types of exoplanets based on the properties we observe. One common type of inner solar system planet — which our own solar system oddly doesn’t contain — is super-Earths. Super-Earths come in two different varieties: low-density “mini-Neptunes”, and rocky super-Earths. Dawson’s simulation and statistical work reveals that these two types of planets likely form via two different modes:

1. Mini-Neptunes likely form before gas has cleared out of the inner solar system. The presence of gas causes the large sizes and low densities of the planets that form in it, and it also damps the extreme aspects of their orbits, causing the planetary systems to be tightly spaced with flat and circular orbits.
2. Rocky super-Earths form after the gas disk has mostly been cleared. The planets have higher densities and smaller radii, and they form with mutually inclined and eccentric orbits that are more widely spaced.

Dawson hopes that the work that she and other researchers are doing studying and modeling inner solar systems will help us to build a unified blueprint for the origins of planetary systems. Such a blueprint would describe how initial conditions (i.e., the disk properties) trigger different physical processes, leading to the diversity of orbits and compositions observed today. From current observations of inner solar systems, we will therefore be able to understand how planetary systems formed.

Dawson has organized a meeting-within-a-meeting at AAS 230 titled Inner Solar Systems, in which speakers are examining a number of open questions about planetary system origins:

#aas230 Amazing line-up of exoplanet experts – faces of the future: pic.twitter.com/LnwDfga9mw

— Meg Urry (@Meg_Urry) June 5, 2017

You can read more about Dawson and her work in an interview by Bhawna Motwani.

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Press Conference: Hot Planets & Cool Dwarfs (by Benny Tsang)

The second press conference of the day was on hot planets and cool stars, and the boundary between the two. We had four speakers presenting three exciting pieces of work. Scott Gaudi (Ohio State University) and Karen Collins (Vanderbilt University) first talked about the discovery of a gas-giant planet that is hotter than most stars. They are part of a collaboration called KELT — an all-sky survey for transiting planets around bright stars. KELT-9b is a gas giant planet orbiting around a hot star. It has 3x the mass and 2x the size of Jupiter. The planet is tidally locked to its host star, with a day-side temperature of ~7,800 ℉ (just slightly cooler than the Sun’s ~9,800 ℉). Another exotic aspect of this planet is that its orbit is perpendicular to the host star’s equator. Given the brightness of this system, it has tremendous prospects for more detailed studies! [Full press release]

Giovanni Bruno (Space Telescope Science Institute) then took us on a tour to learn about his study on clouds in exoplanets — a unique window to planet atmospheres. WASP-67 b and HAT-P-38 b are two similar Jupiter-size planets orbiting close to their host stars. By contrasting their transit depths at different wavelengths, 67 b was found to have stronger water absorption, hinting at a higher metallicity and possibly a higher cloud deck! Such differences may be attributed to their distinct formation and accretion histories. Future observations and better models will help us to better understand the driving forces of these extraterrestrial weather patterns. [Full press release]

For decades, astronomers weren’t quite certain where the line between stars and planets was. Below a certain mass limit, the central temperature of a cloud of gas is not high enough to ignite hydrogen fusion, which results in objects known as brown dwarfs (a.k.a. failed stars). By observing binary star–planet systems, Trent Dupuy (the University of Texas at Austin) was able to make the first empirical constraint on this minimum mass limit. It is found that the minimum mass for stars to shine is ~70x the mass of the Sun, which is lower than the commonly quoted value of 75x. It implies that we actually have more stars in the Universe, i.e. more hosts for life! [Full press release]

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Plenary Session: The Universe’s Most Extreme Star‐Forming Galaxies (by Benny Tsang)

Prof. Caitlin Casey (University of Texas, Austin) is much more than an exceptional scientist and educator, she is also the driving force of many efforts on equity and inclusion. She started the plenary session by welcoming everyone to the great city of Austin! Her talk was on the most actively star-forming galaxies in the Universe. Our Milky Way Galaxy typically makes about one solar mass worth of stars per year, but these extreme galaxies make up to more than a thousand times more stars per year! Stars are the fundamental building blocks of the Universe, and understanding these extreme galaxies helps us put together a complete picture of galaxy growth in the context of cosmology.

It turns out these productive stellar nurseries in the early Universe are very dusty. In these Dusty Star-Forming Galaxies (DSFGs), almost all visible starlight is absorbed by the dust and gas of the interstellar space. By focusing our attention to longer wavelengths, we pick up signatures from the assembly of early galaxies which are otherwise unavailable. It actually came as a surprise when astronomers observed galaxies in millimeter wavelengths and found that they are really luminous! The bright millimeter emission comes from the re-emitted radiation from stars by dust, which closely relates to how active star formation is in these galaxies.

In the talk Casey summarized her endeavor to answer three pressing questions.

1. What physics drive DSFGs’ extreme luminosities?
   Answer: When the Universe was young, galaxy mergers seemed to be commonplace. Through the challenging work looking into the morphology (appearance) and kinematics (gas motion) of the galaxies, it seems like most DSFGs are merger-driven, although there are some puzzling counterexamples.
2. How common are DSFGs in the early Universe?
   Answer: They appear quite early in the Universe. We need better census of DSFGs, especially during the epoch reionization, to better understand the formation of the first generation of stars and the gas from which they were born.
3. 

   Casey talks about the TAURUS program, a pioneering program with the aim of viewing the Universe through an inclusive perspective.

   Where do DSFGs live? (How can we leverage them to learn about the assembly of galaxies in the cosmological context?)
   Answer: They mostly live and grow at the densest nodes of the cosmic web. In fact more DSFGs were found in the dense nodes than expected. Again we need better observational constraints on the collapse and build-up of large scale structures.

“We don’t understand galaxy formation and evolution until we understand gas and dust”, she remarked and motivated for a more comprehensive mapping of gas and dust in the Universe. After all, they are what stars and galaxies are built from.

Casey is also the leader of the TAURUS program, a 9-week, one-on-one summer research and mentorship program for underrepresented students here in Austin. To learn more, you can check out her interview by Gourav Khullar.

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Plenary Session: Science Highlights from SOFIA (by Susanna Kohler)

The final plenary of the day was given by Erick Young of the Universities Space Research Association (USRA), here to tell us about the latest science highlights from the SOFIA mission.

Young: "SOFIA is flying — and it has a hole in the side of it the size of a garage door. I find that a remarkable accomplishment." #aas230 pic.twitter.com/WdjHkPhrD0

— AAS Nova (@AASNova) June 5, 2017

SOFIA, or the Stratospheric Observatory For Infrared Astronomy, is a 2.5-m telescope and a collection of instruments flown on a Boeing 747SP wide-body aircraft, allowing scientists to make infrared astronomical observations at an altitude of about 41,000 ft — i.e., above the majority of the water vapor in the Earth’s atmosphere.

What science has been done with SOFIA? It’s used to study a broad range of topics, but Young argues that its science goals can generally be distilled to one line: SOFIA explores the life cycle of matter in galaxies. Young spent the remainder of the talk presenting specific observations and discoveries made with SOFIA. A few examples include:

1. Mapping of the galaxy M51 — in particular, looking at the development and formation of stars in the galaxy’s spiral arms.
2. Observations of the dust clumps in the Circumnuclear Dust Ring at the center of our galaxy. These clumps are too tenuous to survive a complete orbit, so they must be somehow regenerated.
3. Observations of dust in a supernova remnant only 10,000 years old. These data suggest that supernovae might be the primary contributor of the dust observed in distant galaxies in the very early universe.
4. A look at gas infall as a cloud collapses to form stars. SOFIA data allows us to map out the geometry and dynamics of this process better.
5. Occultation measurements of a star by Pluto, which allowed us to learn about Pluto’s atmosphere before New Horizons arrived. SOFIA will try to repeat this feat next month by observing an occultation of the Kuiper Belt Object MU69, New Horizons’s next target.

SOFIA’s missions are user-driven, with the community of infrared astronomers submitting proposals for new targets to study. In addition, the observatory serves as an excellent platform for infrared instrument development. Young’s talk clearly demonstrated that SOFIA’s wide array of instruments and unique follow-the-science mobility has produced a broad range of results that wouldn’t have been possible with a traditional ground-based facility.

You can read more about Young and his work in an interview by Amber Hornsby.

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

— NASASunEarth (@NASASunEarth) 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.