Welcome to the Astrobites coverage of virtual events based around the cancelled American Astronomical Society (AAS) meeting! We will report on highlights from each day here, from AAS Press Conferences to grassroots astronomy community meet-ups. If you’d like to see more timely updates during the day, we encourage you to search the #aas239 hashtag on twitter. We’ll be posting once a day during the week, so be sure to visit the site often to catch all the news!
Press Conference: SDSS: Passing the Torch to Phase 5 (by Katya Gozman)
Today’s first press conference focused on the culmination of the last 12 years of the Sloan Digital Sky Survey (SDSS), one of the largest imaging and spectroscopic endeavours, and also the beginning of a new phase of the survey, SDSS-V! The latest SDSS data release, DR17, alone brought us an overwhelming 245TB of data, almost half of the entire 407TB collected in all the previous releases combined. Though this might seem small compared to the amount of data LSST expects to collect, this is quite astounding for the amount of resources that SDSS had available. Over the years, it has acquired more than 5 million spectra of stars and galaxies, all helping us understand the history of the Milky Way and other galaxies. SDSS is special in that it doesn’t just observe one object at a time. Instead, telescopes are fitted with plug plates containing holes drilled into them at the exact positions of any objects the SDSS team wants to observe. These holes are plugged in with fiber optical cables that lead back to a spectrograph slit, enabling us to take spectra of hundreds of objects at once!
The first speaker, Rachael Beaton of Princeton University and Carnegie Observatories, told us about the APOGEE survey, one of the three SDSS surveys discussed in today’s conference. She explained that APOGEE is unique because it takes data in infrared (IR) light, which lets us look through the opaque, interstellar dust that permeates parts of the Milky Way and see stars embedded in these regions. This survey uses telescopes in both New Mexico and Chile, letting us observe the entire Milky Way by gathering spectra from both hemispheres, and has looked at over 2000 individual fields in the sky. Rachael pointed out that the nearly 2.6 million spectra taken for APOGEE has let us classify and map out the motions of stars and measure the abundances of 20 different elements in stars, 6 of which are the most common elements in the human body. One of the most exciting moments was seeing the final map of all the stars that APOGEE has observed. APOGEE’s coverage extends not only out to the outskirts of the Milky Way, a region that we call the galactic halo, but also far beyond – including satellite galaxies like the Magellanic Clouds and parts of the Andromeda Galaxy! All of this stellar data (no pun intended) lets us learn all about the ages of stars, what they’re made of, and how they move around our galaxy.
The second speaker was Karen Masters from Haverford College, who talked about the MaNGA survey. While APOGEE focused on our Milky Way, MaNGA zooms out to map other nearby galaxies. It takes multiple spectra of a galaxy at once, giving us data for different regions of the galaxy and acting as a sort of barcode for a galaxy. Spectra give us information on the ages, chemistry, and motion of stars, sources of ionized gas, and more. All the spectra for a given galaxy are then packed into a datacube, giving us a little “book of information” about its different parts. Using SDSS’s plug plates, MaNGA can observe 17 galaxies at once, with tens of spectra per galaxy! The MaNGA team also released its Stellar Library, a collection of spectra of individual stars in different galaxies. If any of this sounds really cool, you can access any of the MaNGA data using Marvin, a freely accessible web tool and python module that lets you explore any galaxy in the survey and its corresponding spectra.
The last speaker of the event was Juna Kollmeier from the University of Toronto, who ended by looking toward the future with the newest Sloan program, SDSS-V (see this astrobite about the SDSS-V paper!). This next generation survey will focus on three different programs:
- the Milky Way Mapper, which will probe the formation and evolution of our galaxy,
- The Local Volume Mapper, which will look at the interplay between stars and the interstellar medium and explore star formation, and
- the Black Hole mapper, which will let us understand how both large and small black holes grow over time.
Instead of using plug plates, which have to be drilled months in advance and take a lot of time to change out during a night of observation, SDSS-V will pioneer the use of robotic positioning which lets them change the configuration of fiber optic cables in a flash, making it easy to change targets at the last minute. Even though the pandemic slowed down the development, the SDSS-V team found creative ways to power through and turn their initial whiteboard drawings and models into the final products freshly installed at the Apache Point Observatory.
Over the last decade, SDSS has enabled astronomers to better understand the colors of galaxies and asteroseismology, find differing stellar populations in our galaxy and previously undiscovered star systems, and really map out the large scale structure of the universe. But the speakers also emphasized one of the most important advances SDSS has made for the astronomical community: making data publicly available and accessible so that both astronomers and the public can learn how to use the data and help advance our understanding of the universe!
NASA Astrophysics Town Hall (by Ali Crisp)
This NASA Town Hall was led by Astrophysics Division director Dr. Paul Hertz, with assistance from the division’s chief scientist, Dr. Eric Smith. The slides and Q&A from the Town Hall are publicly available, and can be found here and here.
The purpose of the Town Hall was primarily to provide updates on NASA’s plans from the Astro2020 decadal survey results and to give a brief overview of what they will be doing this year. Updates on suborbital and CubeSat launches were first on the agenda, with Dr. Hertz discussing the four balloon launches and five sounding rocket launches that will take place this year. He then gave a brief update on the CUTE satellite and the Imaging X-ray Polarimetry Explorer (IXPE). A large portion of the mission updates section was spent on JWST, with discussion of the launch and deployment led by Dr. Smith. As of the Town Hall, the launch and deployment of JWST have both been successful, current telemetry data is nominal, and the commissioning steps can safely begin.
Much of the Town Hall was devoted to outlining the programs and initiatives NASA will be starting based on the results of Astro2020. Key points and initiatives from the briefing are:
- NASA is committed to improving inclusion, diversity, equity, and accessibility (IDEA) in the field, and has started (or will be starting) several related initiatives, including increasing funding to bridge programs and early career scientists, instituting double-blind peer review for proposals, and commissioning a separate study on making the proposal system more equitable through the National Academies.
- Work is currently being done to broaden technological development and prepare for future large surveys and major observatories. Future proposal calls will emphasize priority areas that complement the recommendations of the decadal survey.
- Rather than coming up with the next big thing for after the Nancy Grace Roman Space Telescope, NASA will be focusing its efforts on making sure the technology and finances are in place for its development, as well as for other currently planned missions.
There were many other smaller updates during the Town Hall, including how open source science initiatives are progressing and that the review of the Hubble Fellowship Program has been completed. Overall, there seem to be big plans for the coming year in NASA Astrophysics! A recording of the Town Hall will be posted later, so be on the lookout if you’re interested in hearing more. In addition to the live Q&A today, answers to all questions will be posted on the Q&A portal during the coming days.
Live-tweeting by Ali Crisp
Press Conference: Stellar Nurseries, Clusters & Streams (by Macy Huston)
The second press conference today focused on star formation and clusters. Zhuo Chen from the University of California, Los Angeles presented recent work on the star formation history of the central region of our Galaxy. The Milky Way’s central nuclear star cluster is the densest stellar region in our Galaxy, also containing a 4 million solar mass supermassive black hole (SMBH). How did these stars get here, and how do they interact with the SMBH? Chen et al. study star formation history by measuring the abundances of metals (elements heavier than helium) in stars. They found that the nuclear star cluster consists of two populations of stars: 92% metal-rich stars that are 4-billion years old and 8% metal-poor stars between 1-4 billion years old. The former’s age estimate is significantly lower than the previous estimate of 7 billion years. This challenges prior theories about the cluster’s formation, including mutual evolution with the SMBH and inner bulge, as well as the globular cluster infalling scenario. More accurate knowledge of the age of these stars allows for more accurate predictions of the numbers of compact objects and rate of gravitational wave mergers. Future work on faint stars with JWST and on modelling metal-rich stars will further improve our understanding of this region’s star formation history.
Next, Shuo Zhang from Bard College discussed how giant molecular clouds can reveal details of our Galaxy’s central supermassive black hole, Sagittarius A*’s, past. At the center of our Galaxy lies a 100 parsec elliptical and twisted ring of dense molecular clouds, containing 5-10% of the Galaxy’s gas. This cool gas shows bright, variable x-ray emission. Gas this cool couldn’t produce x-rays on its own, so where does the emission come from? A likely explanation is that this gas is reflecting incoming emission from a previously more energetic Sgr A*. Observations suggest that Sgr A*’s x-ray activity has been decreasing over the past few centuries. Zhang and collaborators focused on two molecular clouds in this work. The first is Sgr B2, which shows a peak outburst about 110 years ago and decay over the past 2 decades. The second is Bridge, which shows brightening over the past 20 years. So, what does the difference between these two clouds tell us? Rough estimates of molecular cloud distance estimate that Sgr B2 is closer to us, relative to the Galactic center, while Bridge is further. This would mean that they are reflecting different points in Sgr A’s past. Sgr B2 shows a ~100 year old outburst, while Bridge’s is ~400 years old. Ultimately, the question remains of whether these clouds really tell Sgr A*’s stories at different points in time, and, more importantly, what caused these outbursts.
Next, Allison Hughes from the University of Arizona presented a search for globular clusters in the Centaurus A (CenA) Galaxy. CenA is an elliptical galaxy ~12 million light years from us which shows evidence of substantial galactic merger events. While we can’t resolve individual stars at this distance, we can study its globular clusters. Globular clusters are tightly packed enough to remain intact despite merger events, allowing for the study of stars in these complex merged systems. CenA has many hundreds of globular clusters, as well as halo substructure at large distances. They used PISCeS (the Panoramic Imaging Survey of Centaurus and Sculptor) and Gaia observations, as well as the NOAO source catalog, to identify globular cluster candidates. Spectroscopic follow-up of these candidates is underway to confirm their association with CenA, and over 100 have already been confirmed! These globular clusters and their velocities will be used to uncover CenA’s formation history, and this method can be extended to more galaxies in the future, such as Sculptor, M81, and M91.
The final speaker for today’s press conference was Ting Li from the University of Toronto, who presented the Southern Stellar Stream Spectroscopic Survey (S5)’s progress so far. This project, which began in 2018 and is still ongoing, has so far performed a homogeneous study of 12 stellar streams, seeking to reveal the “feeding habits” of the Milky Way, as well as its dark matter distribution. When neighboring satellite galaxies and stellar clusters get torn apart by the Milky Way’s gravity, they turn into elongated stellar “streams.” S5 studies these streams’ 3D positions, velocities, and chemistry in order to characterize where they came from and how they were gravitationally perturbed. The kinematics of these stellar streams are being analyzed in order to map the distribution of dark matter in the Milky Way.
Chicago Press Release | U. Toronto Press Release | Lowell Observatory Press Release
Astronomy, A Gathering (a.k.a. Nay-A-S) (by Briley Lewis)
Upon the announcement of the cancellation of AAS 239’s in-person meeting, many astronomers took to Twitter to grieve the loss of yet another chance to see their collaborators, colleagues, and friends. It’s now been two full years since we were able to gather in person, and although safety for all community members is the priority, it’s still a loss worth acknowledging. Networking, community, and informal interactions are the aspects of in-person conferences that many find most valuable, yet they are often the aspects left out when events abruptly transition to virtual platforms.
James Davenport, Research Assistant Professor at University of Washington, took it upon himself to create a space this week where astronomers could hopefully find some of the community they were missing with the absence of AAS 239. “I heard so many people sad about losing the opportunity to socialize and network, especially students who are trying to get a foothold into this career…” he said. “I felt like it was worth my time to try and help out.” And thus, Astronomy: A Gathering (a.k.a. Nay-A-S) was born!
This informal networking space, hosted on Gather.Town, was open all day on Tuesday for folks to meander, chat, and hang out. It was an experiment of a virtual professional gathering, hopefully paving the way for future uses of online spaces to create inclusive and welcoming environments. Gather.Town is an interactive platform, where you create an avatar and actually walk around inside a virtual world. Davenport had the Nay-A-S space set up with cafes, private rooms for meetings, a plenary hall, poster spaces, and even a snowy outdoors. There were no organized sessions or activities planned, since this was a small grassroots effort, but instead the space was kept open for whatever the community wanted to use it for. As Davenport says, “I think this is a good demo of what this kind of event can be, and I hope AAS will be interested in a poster event or something similar in the next couple months!”
Community members expressed excitement for the event on Twitter, grateful for a dedicated space for networking and gathering. Mark Dodici, an undergraduate at Princeton, said, “AAS 239 was going to be my first conference, and I was really looking forward to taking some time to just take it all in and connect with the community. I’m hoping that this event will give at least a little taste of that.” Laura Lopez, part of the AAS 239 Cancellation Task Force, said she planned to attend to get ideas for how to run virtual events. Others, like Mallory Molina, were hoping that this gathering could help with networking for those on the job market. Many were just hoping for some human connection; like Astrobiter and West Virginia University graduate student Graham Doskoch said, “For me, it’s about the human connection and really feeling a part of the astronomy community…there’s a difference between staying up-to-date on astronomy and actually feeling like an astronomer, particularly for those of us early in grad school and not in huge departments.”
Here’s hoping today’s event opens the doors for more robust, enjoyable, and accessible networking and community events for the future! And no matter what, thank you to everyone trying to find ways for us to build community, especially in these challenging times.