Editor’s Note: This week we’re at the 241st AAS meeting in Seattle, WA, and online. Along with a team of authors from Astrobites, we will be writing updates on selected events at the meeting and posting each day. Follow along here or at astrobites.com for daily summaries, or follow @astrobites on Twitter for live coverage. The usual posting schedule for AAS Nova will resume on January 18th.
The big takeaway here is that we’ve done some incredible things as a community, and we have so much more to come. “Celebrate, and then write proposals!” he told the astronomers in the audience. “We’re just getting started.”
Press Conference: Clouds and Nebulae (by Pratik Gandhi)
One of the final press conferences of the 241st AAS was focused on clouds and nebulae, and by extension supernovae and other processes that lead to the formation of clouds and nebulae.
Dr. Gerrit Verschuur and Dr. Joan Schmelz were first up, showing new results on distance measurements to the high-velocity cloud (HVC) complex M. This year marks the 60th anniversary of the discovery of this HVC in the Milky Way, and its velocity is much higher than the rotational velocity of the galaxy. Their team made the first-ever distance estimate for any HVC, and they found that there is a stream of gas between the star MI and the gas filament (which is now called Complex M). Radio data also shows that there is a large cavity associated with the complex, which appears to be the result of a supernova that exploded 4 million years ago! The team also inferred a distance of 307 parsecs and a total supernova energy output of 3.5 x 1050 erg. Finally, they concluded by mentioning that the “Local Chimney,” a low-density extension of the well-known “Local Bubble,” likely came from this progenitor supernova.
Next, Dr. Robert Fesen talked about the exceptional supernova remnant Pa 30. This remnant is really interesting because it was discovered in 2013 by amateur astronomer D. Patchick using data from the WISE mission. In recent years, different teams from Hong Kong, France, and Russia discovered a really unusual massive white dwarf star at the center of the remnant, with some astounding properties like really high-velocity winds and high luminosity. This star could be the product of the merger of two white dwarfs, resulting in a rare Type Iax supernova. The other really fascinating thing about this supernova is that it likely happened only a thousand years ago, which is really recent on galactic timescales!
Dr. Bruce Balick continued the press conference with a talk on “The tempestuous life of the Butterfly Nebula, NGC 6302.” Although his take on it was that it “doesn’t look like much of a butterfly, but rather a dragon sneezing fire all around it.” This nebula is an example of an unexpected stellar evolution result. While most planetary nebulae are symmetrical and formed gently (not from explosions), the Butterfly Nebula is asymmetric, much bigger, and a lot more chaotic. Their team compared Hubble Space Telescope images from 2009 and 2020 and found that there appear to be multiple outflows of gas and other material from the central regions, with different outflows having different directions and different ages. Dr. Balick concluded by saying that observations of the Butterfly Nebula are compatible with a rare triple-star accretion disk model, while single and binary star models are too simplistic to be applicable and do not explain all the observed features.
The final presentation was by Dr. Peter Barnes, who talked about “the case of the masquerading monster in BYF 73.” Cloud BYF 73 is a massive cloud about 8,000 light-years away, with an associated nebula. The mystery associated with it is an inflow of material towards the center, which happens to be the highest rate of mass inflow towards a protostellar object ever seen! Their team used observations from the SOFIA and ALMA observatories, and found strong polarization of magnetic fields in the nebula, and weak polarization in the protostellar core. They also found that the gas infall towards the center is faster than expected, implying a 4–6 times larger protostellar mass than thought, of about 1,000 solar masses. Thus the central protostellar object has been labeled a “masquerading monster”!
Dr. Sangeeta Malhotra kicked off her plenary talk, “Tiny Mighty Galaxies,” by promising many vegetable puns and a little bit of science. Dr. Malhotra is a researcher at the NASA Goddard Space Flight Center and works on low mass galaxies. She grew up in Delhi, earned her PhD in Astrophysics from Princeton University (becoming the first woman of color to do so!), and was part of the inaugural class of American Astronomical Society fellows. She was previously a professor at Arizona State University and moved to Goddard to work on the Nancy Grace Roman Telescope (formerly WFIRST).
Dr. Malhotra’s research focuses on Lyman-alpha (Lya) galaxies. The Lyman-alpha line is a spectral line of hydrogen; Lya photons are created when electrons fall from the second energy level down to the ground state. Any star-forming galaxy can make Lya photons, so Lya galaxies are just the particular cases where Lya photons are able to escape the galaxy and be observed. Figuring out exactly what allows Lya to escape some galaxies but not others is an open question. Dr. Malhotra showed that Lya galaxies have some common characteristics — they tend to be small in size, with low metallicity and low dust content. Additionally, many Lya galaxies are young, with low stellar masses but high gas pressure and strong emission lines, hence the label “Tiny Mighty Galaxies.”
Lya galaxies are cosmologically important because they help us understand the process of reionization by providing constraints on the amount of neutral hydrogen present at a given time. Connecting the galaxies with reionization requires a really good understanding of the physics of Lya escape, and that’s where the vegetables come in! Over the course of Galaxy Zoo, a citizen science project tasked to identify and categorize galaxies, members of the public helped find a new kind of galaxy, affectionately named “Green Peas.” Green Pea galaxies are small, round, and green in color, hence the name. They have very strong emission lines, particularly ones produced by oxygen. They also happen to be a very good local universe counterpart to the high-redshift Lya galaxies used for reionization studies. Dr. Malhotra’s group uses Green Peas to test their models of Lya escape and have found that factors such as dust content and peak velocities are some of the best determinants of Lya escape.
The other component needed to connect Lya galaxies and reionization is a large sample of Lya galaxies at high redshift. Dr. Malhotra is working on this via the LAGER survey, which aims to find Lya galaxies at a redshift of 7. The survey is an international collaboration and uses a narrow band approach to identify the bright Lya lines in galaxies. Dr. Malhotra’s involvement in the Roman telescope will also be crucial to reionization research as the telescope’s extremely wide field of view will help astronomers understand how reionization occurs on scales spanning many clusters of galaxies.
[Slide by Sangeeta Malhotra]
Finally, Dr. Malhotra closed her talk by urging senior scientists to put effort into the retention of students of marginalized identities. She presented a summary of her own previous mentees and showed that the majority of women and students of color have since left the field. She reminded students to prioritize their own mental and physical health, and to ask for help as needed, but stressed that the responsibility for the problem is absolutely on senior faculty. She called on mentors to take notice of any similar trends amongst their own students and to get to work solving this issue in astronomy.
Press Conference: Signals from Neutron Stars and Black Holes (by Graham Doskoch)
The final press conference of AAS241 focused on compact objects: black holes and neutron stars. Four speakers took the podium, presenting discoveries of several new types of astronomical objects — and a couple of old favorites. First up was Prof. Eric Coughlin of Syracuse University. Prof. Coughlin and collaborators studied a tidal disruption event, or TDE, called AT2018fyk. TDEs occur when a supermassive black hole tears apart a nearby star, feasting on its gas and emitting a high-energy outburst. These are usually cataclysmic events, but the group noticed that 600 days after the outburst, AT2018fyk dimmed — and then experienced another, similar outburst 600 days later.
This isn’t supposed to happen with TDEs! The group proposed a model to explain this repetition: a partially disrupted TDE. A star near the supermassive black hole was tidally disrupted, but only partially; some of its gaseous envelope was accreted, leaving a partially-stripped remnant that kept circling the black hole on a 1,200-day orbit. One orbit later, it was once again disrupted. The model predicts that there should be another event this coming August. Will it happen? We’ll have to wait and see.
The next speaker was Emily Engelthaler, of the Center for Astrophysics | Harvard & Smithsonian. She had performed ultraviolet spectroscopy of another TDE (this time not a repeater!). The emission showed a number of expected features, including carbon lines, showing the fast-moving material in the black hole’s accretion disk. What was interesting was the amount of variability, and the eventual disappearance of this carbon emission. Engelthaler proposed that the “puffy doughnut” of material is getting less “puffy,” leading to changes in the spectral absorption and emission.
Engelthaler was followed by Rose Xu, an undergraduate at Bard College. Xu presented results on X-ray flares from Sagittarius A*, the supermassive black hole at the center of the Milky Way. While Sgr A* isn’t as active as many others of its kind, it does exhibit X-ray and infrared flares on a roughly daily basis. Xu was interested in addressing an unresolved question: What’s the mechanism behind these flares? She and her collaborators searched data from the NuSTAR X-ray telescope, discovering seven new flares from 2016 to 2022, including a double-peaked flare. The ground found tentative evidence that bright flares and faint flares may have spectral differences, a hint that they could be caused by different processes.
The final speaker, Dr. Amruta Jaodand of Caltech, presented new results on an unusual pulsar, J1023+0038. Pulsars are the dense, rapidly rotating remains of massive stars, and they emit beams of electromagnetic waves, which sweep across our line of sight, like a lighthouse. This appears as periodic emission, usually at radio wavelengths but occasionally in X-rays and the optical. A subclass of pulsars, millisecond pulsars, spin several hundreds of times per second, after accreting material — and angular momentum — from a companion.
J1023+0038 is a type of millisecond pulsar called a transitional millisecond pulsar. It’s in the process of this accretion, and switches between different modes, one involving X-ray emission and one involving radio emission. Jaodand found that the pulsar also emits ultraviolet pulses; while it’s not the first known UV pulsar, it is the first known UV millisecond pulsar. Coupled with its strange X-ray and radio behavior, this may give insight into pulsar emission mechanisms.
Plenary Lecture: Dan Foreman-Mackey (Flatiron Institute) (by Mark Popinchalk)
When Dr. Dan Foreman-Mackey showed a functioning code block on one of his first slides, he whimsically remarked “I don’t think any other plenary has put Python code in their talk,” which was met with a round of laughter. And it’s probably because no other plenary was trying to do what Foreman-Mackey did — spend 40 minutes presenting the motivations, grand ideas, and power of the open source software he’s worked on in his career.
The scientific example that was used was using Gaussian processes to fit a Kepler light curve showing a transiting planet. But that quickly became a background feature to the three Gaussian-process libraries that Foreman-Mackey had created at different stages in his career; george, celerite, and tinygp.
With his natural charm he carefully laid out the major improvements that each of the three packages incorporated into the computation of Gaussian processes. george made a step away from rote implementation, instead offering a library of kernels (tools used to construct the Gaussian-process model). celerite (“Imagine there are accents if you want to pronounce it properly [i.e., celerité]”) used linear algebra to speed up the Gaussian-process calculation, and tinygp used JAX at its core to speed it up even further.
But it wasn’t the technical achievements that were the most impressive. It was the intention behind the packages that truly shined the brightest throughout the plenary. Foreman-Mackey is a champion of open-source software, where the codebase is public, documented, and easily accessible. Some might cringe at the thought of all their work laid bare for anyone to scrutinize. However, it was clear that Foreman-Mackey thought this was a strength. That a code was made for others meant that it needed to be flexible, that public eyes would find the room for improvements and innovations, that there is a strength in trusting the community of your peers.
This wasn’t a plenary on a topic so much as it was a plenary on a way of working. Littered with little jokes, personal anecdotes, and even more lines of code, the talk wasn’t about empowering the audience with knowledge, but encouraging them to try new code and ultimately experience the ecosystem of open-source coding of which Foreman-Mackey is a clear and vocal champion.
Berkeley Prize Lecture: Anthony Brown (Leiden University) (by Ali Crisp)
Dr. Anthony Brown gave his plenary on the Gaia mission, for which he and his team were being awarded the AAS Berkeley Prize. He began with an overview of the mission, including a joking remark thanking the JWST team for putting their telescope at L2 (where Gaia is also located) so he doesn’t have to explain what that means in his talks anymore. He emphasized the teamwork aspect of the Gaia mission, listing all the different teams in the Gaia Data Processing and Analysis Consortium (Gaia DPAC) and their contributions to the project.
A group picture of the Gaia collaboration. [Slide by Anthony Brown]
Dr. Brown then gave an overview of the data Gaia has collected so far and all the different astrophysical parameters it gathers. To date, Gaia has measured fundamental parameters such as stellar radii and temperature for over 471 million stars. Of those 471 million stars, there are also 2.5 million stars with detailed chemical abundance measurements, 1 million stars with high-resolution spectra, and 219 million star with low-resolution spectra. 800,000 binary systems have also been cataloged in the mission!
Dr. Brown continued by highlighting Gaia science contributions, starting with providing astrometric measurements of Arrokoth to the New Horizons team, so they could make accurate orbital calculations for the spacecraft’s approach. Gaia data were also used to calculate the precise luminosity functions required to confirm that carbon–oxygen white dwarfs undergo crystallization in their interiors. Gaia’s precise astrometry has also been used to confirm the existence of a black hole, to make 3D maps of nebulae such as Orion, and to build clearer pictures of how different elements are distributed in the Milky Way, which in turn give us a better idea of the galaxy’s formation history.
Dr. Brown ended his talk by listing what new data products will be included in the fourth and fifth Gaia data releases, including updated astrometry, time-series data, and much, much more. He kindly requests that — should you use Gaia data for your research — you give the team credit for their hard work. Specific information on how to acknowledge Gaia can be found here.
Editor’s Note: This week we’re at the 241st AAS meeting in Seattle, WA, and online. Along with a team of authors from Astrobites, we will be writing updates on selected events at the meeting and posting each day. Follow along here or at astrobites.com for daily summaries, or follow @astrobites on Twitter for live coverage. The usual posting schedule for AAS Nova will resume on January 18th.
Royal Astronomical Society Gold Medal Lecture: George Efstathiou (University of Cambridge) (by Yoni Brande)
Professor George Efstathiou is the 2022 Royal Astronomical Society Gold Medal awardee, and as part of this honor, he was invited to give one of the plenary talks here at the winter AAS meeting. Prof. Efstathiou is Professor of Astronomy at the Institute of Astronomy at Cambridge, and he was director of the Institute from 2004 to 2008. His research focuses on cosmology, ranging from simulations of large scale cosmic structure formation to anisotropies in the cosmic microwave background.
Prof. Efstathiou structured his talk around paradigm shifts in cosmology. Fifty-seven years ago, in 1965, Penzias and Wilson discovered the cosmic microwave background (CMB), providing the strongest evidence for the Big Bang theory of the origin of the universe. When Prof. Efstathiou started his PhD a decade later, he worked on early computational models of cosmological structure formation, taking weeks to run on room-sized computers. For comparison, he re-ran some of those models on his laptop, but they only took 30 seconds!
Soon after, inflationary theory was the next paradigm shift in cosmology, which preserved causality in the early universe, linking now-unrelated areas of space with each other just after the universe’s formation. However, while inflation explained the current scale of the fluctuations in the CMB, their origin was still unclear, leading to the development of the modern theory for the quantum generation of those fluctuations, giving modelers initial conditions to tweak for their simulations!
Working from the cold dark matter (CDM) model, Prof. Efstathiou and his group produced a suite of simulations of current-day large scale structure and then conducted a big photometric survey to test their assumptions. They found even more structure in the current universe than they’d predicted, which could only be resolved by a positive cosmological constant, the simplest explanation for dark energy (the Lambda-CDM model).
These theoretical models were quickly tested with even more sophisticated observations, with COBE, WMAP, and Planck measuring the CMB at incredible resolutions, showing spatial invariance and causal connection across the entire sky, with the amplitudes of the fluctuations lending even more support for LCDM and closely matching theoretical predictions.
So, do we actually have a standard model of cosmology? Yes, with some caveats: we don’t really understand inflation, we don’t have a dark matter particle, and we don’t understand dark energy. This raises an uncomfortable question: Is LCDM just a fitting function? Prof. Efstathiou is a bit more optimistic. Each point in the model has lots of indirect observational evidence, so there should be some truth in the model even if we don’t deeply understand the individual ingredients.
A lot of the observational problems need to be resolved. It’s been 25 years since dark energy, the last paradigm shift in cosmology, and who knows where the next one will come from. It’s unlikely that a theorist will come up with something groundbreaking out of nowhere. The Hubble tension still needs to be resolved, and it might be impossible to detect primordial gravitational waves from the CMB. Prof. Efstathiou’s best bet is that the next paradigm shift will be the detection of dark matter. Hopefully, in another 57 years, the RAS Gold Medal winner will step onto the stage at the AAS meeting and give a similar talk, all about how we used to not understand inflation!
Press Conference: Building Systems in Our Local Universe (by Briley Lewis)
This morning’s press conference tackled the building blocks of our universe, from star-forming regions to planet-forming debris disks — including multiple new exciting results from JWST.
JWST images of the AU Microscopii debris disk. [Kellen Lawson]
Kellen Lawson (NASA Goddard Space Flight Center) presented JWST NIRCam observations of the debris disk AU Mic, a well-studied edge on disk with a few planets known from transits. The new JWST images reveal the disk in never-before-seen wavelengths, which are still undergoing analysis. The team didn’t spot any planets, but their sensitivity curves revealed that JWST is now sensitive to solar-system-mass planets at solar system scales, which is exciting!
Jacob Lustig-Yaeger and Erin May (Johns Hopkins University Applied Physics Laboratory) presented new observations of transiting rocky exoplanet LHS 475b, JWST’s first exoplanet discovery and a previously unconfirmed TESS Object of Interest (TOI). This planet is very similar in size to Earth, but much warmer — and with transmission spectroscopy, they peered into its atmosphere. Its spectrum is remarkably flat, consistent with either a fully carbon dioxide atmosphere or even no atmosphere at all. More observations are needed to figure it out!
Margaret Meixner (Universities Space Research Association) revealed a gorgeous new image of star-forming region NGC 346. NGC 346 is the brightest most massive star forming region in the Large Magellanic Cloud, and her team searched for young stellar objects (YSOs) embedded within it. They found so many that the YSO count has grown by a factor of three!
Ümit Kavak (Universities Space Research Association) continued on the theme of star formation, showing data from the airborne observatory SOFIA that reveal huge outflows from the Trapezium stars within the Orion Nebula moving over 60,000 miles per hour. And last but not least, Theo O’Neill (University of Virginia) displayed a new map of the local bubble’s magnetic field. The local bubble was created a long time ago from supernovae (not from the Sun!), and the Sun just happens to be in the middle of it. This map is going to be a useful new tool for astronomers exploring how magnetic fields affect star formation.
Dannie Heineman Prize Lecture: Norman Murray (CITA) (by Graham Doskoch)
Here’s a simple question: Why does one day on Earth last 24 hours? That was the focus of the plenary lecture by Prof. Norman Murray, winner of the Dannie Heineman Prize. It might seem easy to answer, but half a century of work has shown it to be anything but. The solution requires an understanding of tidal forces, atmospheric modeling, and a willingness to think about clams.
Prof. Murray took us to the Pacific Northwest. Clams there grow their shells at different rates depending on nutrient and sediment deposition in the shallows of the ocean; if a clam is eating, it’s growing. This in turn is connected to the height of the tides. By looking at the size of bands in a clam’s shell, you can learn about how the tides have varied over time — which in turn tells you about the orbit of the Moon, since it’s one of the two celestial bodies that cause gravitational tides on Earth.
Clams haven’t lived on Earth since the dawn of time, so if you want to go back further, you need to check the geologic record. By probing the composition of strata, you can grab information about the history of Earth’s climate, from which you can in turn extract data showing the precession of Earth and the Moon. More analysis then lets you model the change in the Moon’s semimajor axis.
If that wasn’t complicated enough, Prof. Murray pointed out that there’s another force affecting Earth’s angular momentum: thermal tides. As the Sun heats Earth’s atmosphere, more complex interactions cause changes in pressure, giving rise to a tidal perturbation. In short, gravitational tides from the Moon extract angular momentum from Earth; thermal tides, on the other hand, add angular momentum.
Some fluid dynamics modeling shows how waves can propagate in the atmosphere, driven by these effects. Prof. Murray showed that they’re subject to a particular resonance determined in part by the speed of sound in the atmosphere. This resonance, coupled with thermal and gravitational tides, eventually drove Earth’s angular momentum to its current point, corresponding to a day of roughly 24 hours. The balance has lasted about 1 billion years, give or take.
There are other interesting facts you can derive from modeling; for example, there’s a temperature dependence on all of this. Plus, by simulating the angular momentum transfers, you can model evolution of the Moon’s orbit — in particular, the change in the Moon’s semimajor axis over time. It’s model-dependent, but the results Prof. Murray presents match experimental data points, to varying degrees of success.
The lunar orbital semimajor axis as a function of time. [Slide by Norman Murray]
STEM Mentorship and Underrepresented Minoritized Students (by Isabella Trierweiler)
This special session included four views on the intersections of mentoring, mental health, and diversity, equity, and inclusion (DEI) work. The first speaker was Jennifer Bates, a social worker and program manager for the Broadening Participation initiative at the National Radio Astronomy Observatory (NRAO). She introduced the motivations for the Broadening Participation Programs, which include five research and mentoring programs to increase representation of students with underrepresented identities in the sciences. She pointed out multiple studies of stress and anxiety amongst college students in general, as well as specifically for BIPOC and LGBTQIA+ students, showing that students or marginalized identities are much more likely to experience discrimination and exclusion but less likely to receive adequate mental health care. Danielle Rowland, who also works on the Broadening Participation Programs at NRAO, then spoke about the NAC (National Astronomy Consortium) program. The program places students into cooperative teams to work on summer research projects. Students also receive mentoring and professional development support and are eligible for further research projects, travel grants, and bridge support for graduate school after their participation in the program.
Timothy Paglione shared his experience running AstroCom NYC, a CUNY program to provide support and mentoring for astrophysics students. The students are paired with research and career mentors and work on research at the American Museum of Natural History. The CUNY system is very extensive, with 25 campuses including senior and community colleges, graduate programs, and professional colleges. The program has grown along with its students’ needs, evolving the approaches to preparing students for graduate school as well as industry jobs and adding a focus on mental health. One of the unique aspects of AstroCom NYC is that the program has a counselor available to serve students’ mental health needs, so that students can attend one-on-one counseling sessions or join a “Solidarity Group.”
Finally, David Morris spoke about his experience growing the physics and astronomy program at the University of Virgin Islands (UVI). UVI is a relatively small university with about 1,500 students, most of whom grew up locally. The degree program in physics, with a concentration in astronomy, just started in 2015 and grew rapidly in its first few years. However, the program faced difficulties when Covid began, and both enrollment in UVI and in the physics program went into a decline. In order to get students involved again and improve recruitment to the physics major, the department started a student-run High Altitude Balloon project. The intensive hands-on experience helped to renew enthusiasm for research amongst the students while giving them the opportunity to work with scientists at other institutions.
Press Conference: Discoveries in the Milky Way’s Backyard and in the Universe at Large (by Mark Popinchalk)
If you are feeling pedantic, you might point out that a press conference called “Discoveries in the Milky Way’s Backyard and in the Universe at Large,” could be more simply called “Discoveries.” But a better name might have been “Galaxies,” as that was the through line between all the presentations.
First was Burçin Mutlu-Pakdil who announced the discovery of three ultra faint galaxies beyond the local group. Ultra faint dwarf galaxies are the most dark matter dominated objects in the galaxy, but are (by definition) faint and small, which makes them challenging to observe. All the previous examples were around galaxies in our local group (essentially the Milky Way, Andromeda, and smaller friends), but the authors identified three new ones around NGC 253 using Hubble images.
Then Dong-Woo Kim introduced us (or at least me) to XBONGs, X-ray Bright Optically Normal Galaxies. They are just that, galaxy-like objects that look normal in optical light, but are extremely bright in X-ray. By combining Chandra data with objects classified as galaxies in SDSS, they found 820 XBONGs and attempted to understand what they were. 50% of them are almost certainly obscured active galactic nuclei, where the optical light is blocked by gas and dust but the X-ray light is penetrating through. The other half is split between likely being hot gas clouds and maybe diluted active galactic nuclei. In the future, they will use more Chandra observations and double the number of XBONGs (so fun to write) for them to classify, and hopefully understand the phenomenon.
Kaixiang Wang then set about revealing the origin of ultra compact dwarf galaxies (UCDs). These objects seem to blur the definition between globular clusters and dwarf galaxies; they have a similar mass to the latter, but their size is an order of magnitude smaller, closer to the former. One theory is that they are former dwarf galaxies that have had their outer layers stripped by a violent tidal interaction in the past, leaving only the nuclear star cluster. The main result is that they found some objects with tidal disruptions and envelopes — smoking-gun evidence that at least some UCDs originate from disrupted nucleated dwarf galaxies.
We then moved from smaller galaxies to some of the bigger players in our own Local Group, the galaxies that are near the Milky Way. Kat Barger started by warning us about the dangers of supernovae winds pushing out gas in the Large Magellanic Cloud galaxy (LMC). Really the danger is to the LMC, as she showed that the winds were heating up gas and shooting it out of the LMC, at least 4.5 times the amount of gas that the LMC is using to make stars and planets! That’s not necessarily bad for its future star formation rate, as the gas might cool and fall back towards the small galaxy, except there is a much bigger galaxy nearby — our own Milky Way! The presentation ended by showing that there is already a large outflow from the LMC that is being tidally pulled by the Milky Way. Thanks for the gas, LMC!
Finally, Adam Smercina wanted to look at spiral structure in low-mass galaxies, such as the LMC, but it’s not a good example in part because of the tidal influences of the Milky Way. So instead he focused on the Triangulum galaxy, another diminutive neighbor. Using a Hubble survey program called PHATTER, he was able to identify 22 million stars individually, and sort them into rough bins of youngest, young, intermediate and old. When he looked at how those populations were positioned in space, the young stars show a clear spiral structure, while the older ones lose their spiralness! This isn’t necessarily an evolutionary sequence, as the older ones might have been disrupted into their blobby distribution. Rather, it’s more likely a trace of the gas in the galaxy, which behaves differently than the stars do.
Overall it was great to see some new results from galaxies that were indeed in the Milky Way’s backyard and beyond!
Plenary Lecture: Chanda Prescod-Weinstein (University of New Hampshire) (by Isabella Trierweiler)
The theme throughout Dr. Chanda Prescod-Weinstein’s plenary talk was that astrophysics and particle physics will become increasingly entangled as the quest to understand dark matter moves forward. Dr. Prescod-Weinstein is a Professor of Physics and a Core Faculty Member in Women’s and Gender Studies at the University of New Hampshire, and author of the popular science book “The Disordered Cosmos: A Journey into Dark Matter, Spacetime, and Dreams Deferred.” She focused her plenary talk on the role of astrophysics in some of the most pressing open questions regarding dark matter.
Dr. Prescod-Weinstein began her talk by introducing dark matter, the mass that we know is prevalent throughout the universe due to its gravitational influence but which does not seem to be explained by any particles in our current standard model. Astrophysical proof of dark matter has existed for some time — we see it in the flattening of galaxy rotation curves, in lensed galaxies imaged by Hubble and JWST, and in the features of the cosmic microwave background. Based on these observations, and through testing dark matter in cosmological simulations, we know that dark matter doesn’t interact with photons and is cold and slow moving.
She stressed that understanding dark matter is not just a goal for particle physicists — astronomers have stakes in the outcome, too. One of the main examples lies in galaxies, whose formation and evolution is deeply dependent on the dark matter halos they reside in. To truly understand the physics of galaxies and their satellites, we need to understand what dark matter is and how it influences its environment.
Amongst the possible components of dark matter, which span in scale from miniscule particles to multiple-solar-mass black holes, Dr. Prescod Weinstein spoke about two promising options: axions and asymmetric dark matter. Axions are theoretical particles that were proposed to solve symmetry issues in quantum field theory. The particles were proposed in the 1980s, but experiments have just recently become capable of searching for them. The idea behind asymmetric dark matter is that, much like particles and anti-particles, dark matter and anti-dark matter both formed in the universe, and in the process of colliding and annihilating, only dark matter was left to survive to present day.
Venn diagram of the possible theories of dark matter. [Slide by Chanda Prescod-Weinstein]
Dr. Prescod Weinstein presented a few astrophysical probes related to each of these potential dark matter components. Interestingly, astronomers can expect neutron stars to play a big role in future dark matter studies. The inner cores of neutron stars are very mysterious, but it could be that they contain dark matter, not just nuclear matter. Additionally, it’s possible that asymmetric dark matter can be made within neutron stars. More higher-energy missions could help us clarify the neutron star/dark matter relation!
Illustration of a neutron star’s interior. [Slide by Chanda Prescod-Weinstein]
Regarding axions, Dr. Prescod Weinstein showed that astronomical-scale manifestations of the particle are certainly possible! Axions are a type of particle called bosons, and because they are bosons they have a special property when cooled to very low temperatures. When bosons (and axions) are near 0 Kelvin they become Bose-Einstein condensates, a particular state of matter where many individual particles group together so that quantum systems can be viewed macroscopically. The exact size of the condensate would depend on the mass of the particle, but axion Bose-Einstein condensates are theorized to be at least as large as an asteroid!
To move forward in these theories, Dr. Prescod Weinstein emphasized the importance of new instruments such as STROBE-X and the Vera Rubin Observatory. Observations from these telescopes will be crucial in fully utilizing astrophysical probes in the search for dark matter!
Dr. Stierwalt began her talk with an overview of dwarf galaxies. She explained that we have recorded evidence of our ancestors observing the Small and Large Magellanic Clouds — two of the most famous dwarf galaxies — dating back to prehistoric times. However, we didn’t know what they or other dwarf galaxies were until Harlow Shapley observed the Sculptor Dwarf Galaxy in 1937.
Moving into the bulk of her talk, Dr. Stierwalt outlined four reasons why dwarf galaxies are both very hard and very important to study:
Dwarf galaxies are both small and faint — two characteristics that can greatly limit the observability of an astronomical object. However, because they are small and faint, we can use them to place stricter constraints on galaxy structure. For instance, we know roughly where dwarf galaxies should be in relation to the Milky Way and how many of them there should be, so if we compare the theoretical distribution to what we actually observe, we can determine how much dark matter must be present to reconcile the difference.
Dwarf galaxies are strongly affected by stellar feedback because their gravitational wells are shallow. In other words, since they’re smaller than other galaxies, they have less gravity and are more affected by events such as supernovae that create turbulence in the interstellar medium. Studying the effects of stellar feedback can tell us more about both the mechanisms creating the feedback and the structure of the dwarf galaxies themselves. This is especially true in relation to dark matter, since we see dwarf galaxies with both low and high amounts of dark matter, and those with seemingly high amounts of dark matter tend to be more isolated, leading astronomers to wonder if stellar feedback is somehow stripping the dwarf galaxies of dark matter.
Dwarf galaxies have low metallicities, so their compositions are similar to those of the highest redshift — i.e., the oldest — galaxies. This similarity means they can give us an idea of how star formation and stellar feedback occurred in the earliest populations. They can also give us insight into how mass loss occurs in low-metallicity stars, and help us discover techniques to find intermediate active galactic nuclei.
Dwarf galaxies are heavily influenced by their environment. In other words, they’re very sensitive to what’s happening around them chemically and dynamically. Mergers of dwarf galaxies, for example, are much more likely to occur than mergers of large galaxies, and have different results. Dwarf galaxy mergers have starbursts occurring earlier in the merger than in mergers of larger galaxies, for example, and create more evenly distributed stars.
In closing, Dr. Stierwalt briefly discussed how upcoming surveys with the Rubin Observatory and the Nancy Grace Roman Space Telescope will increase the number of known dwarf galaxies. Additionally, follow-up observations of known dwarf galaxies using JWST will tell us even more about their dynamics and characteristics. Simulations of dwarf galaxy mergers — thought to be the progenitors of larger galaxies such as the Milky Way — are also becoming more and more accurate as we learn more. It’s an exciting time to be studying these small but mighty galaxies!
Astronomy in Indigenous Communities Special Session [from Tuesday, January 10th](by Macy Huston)
This session was the third of three events at AAS 241 relating to Community Models of Astronomy, following a workshop January 5–6 and the plenary panel on Monday.
Christine Matsuda (Maunakea Observatories) introduced the session, establishing the context of this work from the Astro 2020 decadal survey part 3.4.1. The Community Models of Astronomy workshop focused on strengthening relationships between indigenous communities and the astronomy institutions that exist on their land. The 30-person workshop was hosted by the ‘Imiloa Astronomy Center and Maunakea Observatories, with representation from multiple indigenous communities, as well as indigenous and non-indigenous astronomers and other scientists. Major discussion topics included the difficulty of such relationships, establishing mutual stewardship as opposed to a benefactor/beneficiary relationship, and the misalignment of the pace of this work and institutional timelines. Next steps following the workshop will summarize the ideas discussed and recommendations for the future.
Next, Yuko Kakazu, education and outreach specialist at Thirty Meter Telescope (TMT), spoke about connecting astronomers with Hawaiian students through tutoring. TMT and Mauna Kea have been a source of community division and a symbol of colonialism and injustice since before the 2019 protests. The start of the pandemic in 2020 paused previous interactions. The TMT project manager moved to the community to listen and learn, and a new education and outreach team was established in the area. The pandemic’s impact on education (as Hawaiian schools closed for over a year) saw a decrease in science and math proficiency, particularly among native Hawaiian students and other marginalized groups. The TMT education and outreach group started a tutoring program that reduced the number of students failing classes and helped to establish a sense of community between the astronomers and locals.
The third speaker, Ku’ulei Bezilla (’Imiloa Astronomy Center) presented A Hua He Inoa, which means something like “calling forth a name.” This project at the ‘Imiloa Astronomy Center has worked to reclaim cultural practices in Hawaii, including naming astronomical objects. So far, five student cohorts have gone through the naming process, resulting in six official names: the quasar Pōniuāʻena, the interstellar object ‘Oumuamua, the black hole Pōwehi, the asteroids Kamo’oalewa and Ka’epaoka’āwela, and the dwarf planet Leleākūhonua. The current cohort has submitted the names Leimakua and Kawelo to the 2023 International Astronomical Union ExoWorld naming competition for HAT-P-26 and HAT-P-26b, inspired by a story about family relationships. The group is also working to build an exhibit about light pollution in their community.
The next presentation was about the One Sky Project, given by Ka’iu Kimura (’Imiloa Astronomy Center). This project, which is sponsored by TMT, is bringing together different communities to share stories in planetaria, with the guiding principle: “Everyone sees something a little bit different, but we all see one sky.” Six films have been created so far, based on cultures from Hawai’i, Japan, Navajo, Greece, Canada, and India. The first five films will be released after the final premiere next month, and they will be freely available to planetariums, along with materials to prompt discussion. Ka’iu closed with a mention of the difficulty around this project’s TMT sponsorship given the opposition against its construction on Mauna Kea. But, One Sky Project has appreciated their support and editorial freedom.
The second to last presentation of the session was from Jacelle Ramon-Sauberan. Jacelle is a full-time faculty member at Tohono O’odham Community College who spoke about her work as a part-time communication specialist for NOIRLab/Kitt Peak National Observatory (KPNO). The role provides cultural competency education and helps with relationships between the Tohono O’odham community and KPNO. She showed the new NOIRLab education program logo created by Jeffery Antone Sr., a Tohono O’odham artist. Jacelle also arranged for tribal leaders to visit KPNO for the first time in many years, including Tohono O’odham Nation Chairman Ned Norris Jr., Vice Chairwoman Wavalene Saunders, and Schuk Toak District Leadership. During the Contreras fire at KPNO, the Tohono O’odham nation’s fire department, police, and other entities assisted. Additionally, a medicine person cleansed the mountain and staff after the fire. Jacelle wrapped up with a discussion in-progress updates to KPNO’s land acknowledgement, involving community input, including elders and youths, and translating it to O’odham.
Aparna Venkatesan wrapped up the session with a discussion about the problem of satellite constellations (SatCons). During our ongoing global crises, we have the opportunity to work together and establish better ways of doing things. The SatCon crisis involves the dramatically growing number of satellites in low Earth orbit, threatening astronomy and dark skies everywhere. They cause streaks in images but also contribute to a rise in global brightness, wiping out the “dark sky” regions of the planet. In addition to astronomy, these issues affect cultural sky traditions, human health, and animal behavior, including bird migration. Aparna took part in the Community Engagement working group from the SATCON2 workshop in July 2021. The group examined the future of orbital space in partnerships with indigenous communities, identifying ethical, cultural, and legal issues in the SatCon crisis. She closed with an emphasis on the importance of setting precedents today to work ethically, based on communities, not conquest.
Editor’s Note: This week we’re at the 241st AAS meeting in Seattle, WA, and online. Along with a team of authors from Astrobites, we will be writing updates on selected events at the meeting and posting each day. Follow along here or at astrobites.com for daily summaries, or follow @astrobites on Twitter for live coverage. The usual posting schedule for AAS Nova will resume on January 18th.
Plenary Lecture: Allison Kirkpatrick (University of Kansas) (by Yoni Brande)
Everything I Need to Know About AGN I Learned in this Plenary – Allison Kirkpatrick (Univ. Kansas)
Prof. Allison Kirkpatrick is an expert in active galactic nucleus (AGN) observations and is currently a professor at the University of Kansas, where she leads a vibrant research group and heads the KU REU program. Prof. Kirkpatrick is also deeply involved with early JWST AGN science through the JWST Cosmic Evolution Early Release Science (CEERS) collaboration. Astrobites’s live tweeting of her plenary talk can be found here.
Prof. Kirkpatrick began by highlighting her close collaborators, postdocs, and students, without which none of the groundbreaking work happening in her group would be possible.
AGN are the accreting supermassive black holes (SMBHs) at the centers of galaxies. For example, the SMBH in Messier 87, the first target of the Event Horizon Telescope’s imaging campaign, is roughly the size of the solar system (~300 AU), while its host galaxy is more than 10 million times larger. Despite this disparity, SMBHs often have significant impacts on their host galaxies. Observationally, we can see their indirect effects, such as jets and radio lobes, but we can also classify AGN by their direct properties, such as the presence or absence of broad emission lines.
Finding AGN
We can find AGN by observing in several different bands, anything from the X-rays down into the radio. Different parts of the AGN structure (the dusty torus, corona, BH accretion disk, or clouds in the broad and narrow line regions) tend to emit in specific regions of the electromagnetic spectrum. High X-ray emission from the incredibly hot corona is a good specific tracer of AGN, but X-rays are often absorbed by gas in the interstellar medium, making this method relatively incomplete. Cooler temperatures in ionized clouds lead to broad optical emission lines, but can also be obscured, and spectra are expensive. Narrow lines come from the accretion disk, but some (like H-alpha and H-beta) are also characteristic of star formation, requiring specific line ratios to diagnose AGN versus star forming galaxies. The hot dust in the torus is an infrared emitter (with a classic power law), but it needs to be separated from cold dust in the rest of the galaxy. A major benefit is that infrared AGN aren’t obscured by geometry or other structures in the host galaxy. JWST photometry will be able to tease these apart, so stay tuned for new samples of AGN from Prof. Kirkpatrick’s group!
Unification
The observational types of AGN have historically been thought to be geometric effects, where different viewing angles give us clearer or obscured views through the AGN’s own structure down towards the black hole. However, this isn’t the only explanation: non-unified models posit that, for example, high AGN accretion rates can blow the torus further away, removing it as a source of emission entirely. High galaxy masses and mergers can also deliver more obscuring gas into the galaxy, blocking emission from the AGN externally. These processes can also change over a galaxy’s lifetime, where initially obscured AGN may clear away the gas and dust blocking them, eventually transitioning to an unobscured state.
Mergers
When two gas-rich galaxies collide, the merger process compresses their gas and triggers bursts of star formation. In addition, the merger shunts gas towards their centers, massively growing their SMBHs. Recent studies have shown that this gas also obscures the AGN and is correlated with the dust content of the merging galaxies. However, recent studies have also shown that while mergers are sufficient to fuel AGN, they’re not necessary, with half of the observed low redshift quasars in the Stripe82 sample not present in merging galaxies.
Feedback
Strong AGN emission isn’t just a good observational tracer, but it can also drive powerful winds throughout the galaxy. These winds have been theorized to be able to quench star formation, but it’s hard to definitively measure the mass outflows from these winds. Since star formation also consumes lots of gas mass, AGN winds may not actually be sufficient to quench galaxies, especially at high redshift. AGN can also heat dust throughout the rest of the galaxy, and this itself may also be enough to quench star formation. Since dust and gas tend to coincide, AGN-heated gas may also be present, which has been shown observationally. Each of these feedback mechanisms could explain star formation quenching. While this assumes star formation declines in AGN host galaxies, observations of infrared AGN and X-ray AGN imply that both populations may form stars at typical rates.
The Oddballs
Not all AGN are typical or well-behaved. Prof. Kirkpatrick’s group has identified a population they call “Cold Quasars”: high-luminosity AGN with significant amounts of cold gas and lots of dust (but totally unobscured!)
Inclusion
Closing out her plenary, Prof. Kirkpatrick highlighted some major societal concerns in our field. We can’t separate scientists from their science, and who gets to do science is as important as the discoveries they make. Diversity in the field is low, and historical trends have made astronomy a less-than-hospital place for astronomers of marginalized identities, including but not limited to non-white, non-male, neurodivergent, disabled, queer scientists. These scientists often shoulder disproportionate service efforts, are intentionally or implicitly devalued, and have harder times getting funded.
Luckily, this is a solvable problem. There are great resources available to marginalized students to help find their cohorts, including Black in Astro, NSBP, SACNAS, the Astro Outlist, and others! Allies can also do their best to amplify the voices of our marginalized peers, make our conferences and classrooms more inclusive and accessible, value service work alongside research and teaching for hiring, tenure, and funding, educate ourselves on institutional barriers and how to dismantle them, and learn how to mentor all students effectively. Prof. Kirkpatrick closed with a strong statement: “Our field will only be truly accessible when we decide that people matter more than black holes.”
Patrick Taylor kicked things off by introducing the new radar capabilities of the Green Bank Telescope (GBT). The GBT is currently the world’s largest steerable radio telescope, and it recently got its first prototype radar system, built in collaboration with Raytheon. The new transmitter has less power than a microwave but has already generated some impressive results! To image objects, the GBT works in conjunction with the Very Long Baseline Array (VLBA), with the GBT as a transmitter and VLBA as the receiver. This system resulted in the highest resolution image of the Moon ever taken from Earth, as well as a detailed image of the Tycho crater. The team also demonstrated the GBT transmitter’s use in small-body science by detecting an asteroid five times farther away than the Moon!
Many in the audience were curious about how the GBT system will compare to the recently collapsed Arecibo telescope. Dr. Taylor noted that the GBT is a much smaller telescope, but it does have more flexibility as it is fully steerable (Arecibo had a steerable receiver but the base was built into a sinkhole). He also pointed out the GBT will continue to be used in partnership with the VLBA and eventually the ngVLA. which will bring the whole system’s capabilities in range of Arecibo’s. Designs for the final radar system for the GBT are still in the works, but once the radar system is completed, the GBT could be used for detailed geology and dynamics studies, tracking of space debris and planetary defense, small-body science, and more!
Emily Gilbert, a postdoc at NASA’s Jet Propulsion Laboratory, presented the exciting discovery of the second known Earth-sized planet in a star’s habitable zone! The habitable zone is the area around a host star that is warm enough for planets to host liquid water. Dr. Gilbert used data from TESS to study the planetary system TOI 700. There were previously three known planets in the system, including planet d, the first Earth-sized planet discovered in the habitable zone. Dr. Gilbert analyzed 14 transits’ worth of data in order to detect the new habitable zone planet, which is slightly smaller than Earth and has an orbital period of 28 days.
TOI 700 is scientifically interesting because the host star is very bright and relatively nearby, and the star appears to be fairly inactive, so it should be a very good candidate for follow up observations! Since the system has planets both within and outside of the habitable zone, detailed studies of this system could help astronomers better understand how planets can follow very different evolutionary tracks after being born in the same protoplanetary disk. Dr. Gilbert says further observations of the system are already in the works! She already has 100 hours on ESPRESSO, a spectrograph at the VLT, to calculate masses for the four planets.
Exoplanet Watch is now open to general audiences! The program involves amateur astronomers and members of the general public in the search for exoplanets, with the goal of combining the power of many small telescopes to more efficiently monitor exoplanet transits. Precise transit timings are really crucial for studying exoplanet atmospheres, and now anyone can help out with these studies! Folks with their own telescopes can sign up to contribute data to the project, and anyone without telescope access can help to process the data. All data contributed to the project will be immediately available to everyone, and anyone who volunteers to observe for Exoplanet Watch will be a co-author on any scientific papers that use the data. Exoplanet Watch carried out a test campaign in 2021, combining data from 24 facilities to construct a transit light curve, something that would have taken 2 hours of JWST observing time! Now that the program is open, astronomers will even be able to request observations for particular systems, and will get results more quickly without needing to wait to receive time on a major telescope. The whole system is a really novel way to approach research, allowing astronomers, amateur observers, and the public to all work more closely and collaboratively on astronomy projects. If you would like to get involved in the citizen science project, you can sign up for the Exoplanet Watch Slack here to get started!
Finally, Sasha Hinkley showed the first direct images of a Gaia Exoplanet, HD206893c. The host star was known to have a circumstellar disk, so it was a promising place to look for exoplanets. The Gaia mission takes very precise measurements of stellar positions in the sky, finding planets based on whether the stars wobble. HD206893 was already known to host one planet, but Gaia data suggested there might be another one, so the team turned to precise imaging to find it. They used the GRAVITY instrument on the VLT to image the system, confirming the orbit of the previously discovered planet and making the discovery of the second planet! The new data is incredibly precise — Dr. Hinkley likens it to observing a dime from 60,000 miles away. The discovered planet is very unique — in size it is right on the border between planets and brown dwarfs (and will hopefully help astronomers better understand the differences between the two groups), and there is evidence that it may have nuclear burning ongoing in the core!
Plenary Lecture: Nia Imara (University of California, Santa Cruz) (by Pratik Gandhi)
In her tour de force plenary talk, “A Star is Born,” Prof. Nia Imara provided a comprehensive review of the complex and important field of star formation out of molecular clouds, the relevant open questions, and potential resolutions to those questions. Dr. Imara, a professor at UC Santa Cruz, was the first Black woman to get an astrophysics PhD from UC Berkeley, and she is also an artist, community organizer, and founder of the non-profit Onaketa, which provides free STEM tutoring to Black and brown youth. In a fun yet poignant moment, she kicked off her plenary by taking a selfie with the entire audience and then acknowledged her ancestors, family, and teachers/mentors who have guided her over the years.
Molecular clouds are the birthplaces of stars and an important intermediate regime between galaxies and stars. Dr. Imara pointed out how difficult star formation is to fully understand, because it’s a complex, multi-scale process involving many different physical processes like gravity, fluid dynamics, magnetism, and chemistry. Molecular clouds are the first steps in the process of star formation, as the coldest and densest, and thus self-gravitating, regions of the interstellar medium. A typical molecular cloud is composed of atomic hydrogen (HI), molecular hydrogen (H2), other molecules like carbon monoxide (CO), and dust.
Next, Dr. Imara posed some of the biggest open questions in the field of star formation, such as:
How do stellar nurseries form and evolve?
What is the role of galaxy environment in star formation?
What is the nature of star formation in the early universe?
Why do stars have the masses they do?
How does star formation depend on the structure of molecular clouds?
A really important idea in the field of star formation is the Kennicutt–Schmidt Law, the idea that star formation rates in galaxies are correlated with the distribution of hydrogen gas in them. Molecular clouds tend to be associated with the highest-surface density of HI gas, and thus are thought to be the setting for most of the star formation in galaxies. Dr. Imara’s work in 2016 implied that turbulence in atomic gas is sub-sonic or trans-sonic, and that HI surface density plays a key role in setting the total mass of molecular clouds. Additionally, although the Kennicutt–Schmidt relation applies to galaxies on large scales, it breaks down when you look at smaller scales. The answer here might lie in cloud ages/lifetimes and whether stellar feedback has had enough time to disperse the cloud after star formation.
Dr. Imara highlighted the PHANGS collaboration, one of the most important surveys of molecular clouds and molecular gas in star-forming galaxies outside of the Milky Way. The image below shows the massive improvement in resolution that PHANGS provides relative to older surveys! One of the key results from PHANGS shows higher surface densities of gas in galactic centers, possibly due to bars funneling gas into the centers. Similarly, PHANGS sees higher gas densities in spiral arms relative to the inter-arm regions.
A slide from Dr. Imara’s plenary talk at AAS 241. Comparing PHANGS survey with previous images, it highlights the increase in spatial resolution. [Adapted from Leroy et al. 2021]
Switching gears, Dr. Imara discussed star formation in dwarf (low-mass) galaxies. Dwarf galaxies are excellent labs for studying star formation in chemically young environments because their properties are so different from larger, Milky Way–like galaxies. Dr. Imara hopes that a future PHANGS-like survey focusing on molecular clouds and star formation in dwarf galaxies will transform the field.
Next, Dr. Imara highlighted the rapid onset of star formation in the early universe, which has been discovered in recent years and was unexpected. ALMA and JWST have observed galaxies at very early times with large masses, lots of dust, and rapid star formation.
On a related note, she highlighted the important concept of the initial mass function (IMF). IMF refers to the distribution of stellar masses at formation, which “impacts nearly every area in astronomy,” says Dr. Imara. Its importance cannot be understated, but we still don’t fully understand all of the ideas behind what causes it! STARFORGE, a suite of cutting-edge simulations of molecular clouds and star formation, has shown that stellar feedback and jets from protostars is crucial for determining the resultant IMF of the stars being born, thus making it a self-regulating process.
Segueing into discussing her recent work, Dr. Imara mentions a major challenge in the field: how do we infer 3D properties of molecular clouds from 2D observations? Well, she and her team had the idea of creating 3D-printed stellar nurseries to visualize the properties of molecular clouds! Dr. Imara is looking at the intersection of art and science to understand how various physical properties affect star formation and the structure of molecular clouds. She and her team ran simulations and then used them to generate the 3D prints. This process helped them determine that what appears to be a gas filament can often be a 3D sheet or pancake-like structure of gas.
In her concluding remarks, Dr. Imara highlighted her nonprofit Onaketa that provides free STEM tutoring to Black and brown children. She also highlights the astronomy that her ancestors and people started studying thousands of years ago. “Star formation provides us with a compelling metaphor — we’re all connected across large scales of space and time,” she concluded.
This afternoon, early career scientists from the NASA ExoExplorers program gathered to discuss their perspectives on diversity, equity, and inclusion efforts in astronomy. These talks explored various dimensions of diversity in astronomy, including race, socio-economic status, disability, gender identity, first-generation status, and more.
Caprice Phillips, graduate student at The Ohio State University and vice president of Black In Astro, shared recent updates on the Black In Astro (BIA) organization and how people can get involved in upcoming events. You may be familiar with BIA from their collaborations with us here at Astrobites! David Coria, graduate student at University of Kansas, highlighted minority-focused academic success programs, including a few important to his career: the K-State Developing Scholars Program, the McNair Postbaccalaureate Program, and the Hagan Scholarship Foundation. Coria recommended that faculty build trust with their students and be understanding of obstacles they have faced, and be willing to take on students from academic success programs.
Kiersten Boley, also a graduate student at The Ohio State University, discussed the classic description of the “pipeline” in academia, suggesting that not only is it leaky, but also that it begins even before college. Income and opportunities for science education are deeply intertwined, and begin affecting kids at a young age — the same young ages when they are forming their science identities. Boley suggested that outreach efforts should target these younger kids at lower-income schools, providing them opportunities they may otherwise not experience.
Dr. Kaitlin Rasmussen (who has been featured before on Astrobites!) explored the experiences of trans, non-binary, and other astronomers beyond the gender binary, as also discussed in their Astro2020 White Paper. Rasmussen listed five flaws in astronomers’ studies of gender in the field: that in these studies gender is white, observable, discrete, a statistic, and inconsequential. They recommend involving sociologists in any studies of gender in the field and compensating marginalized students / colleagues for their expertise on their lived experiences.
UCLA grad student and Astrobites writer Briley Lewis (yep, that’s me!) spoke on disability and accessibility, which Astrobites has great resources on in our Beyond bites. I shared my experiences organizing planetarium shows for Deaf and blind audiences, and with the recent University of California strike. Lastly, UNC Chapel Hill grad student Amy Glazier talked about her experiences as a first-generation college student, and the variety of barriers faced by those without the institutional know-how and lots of unknown unknowns about how to navigate higher education. “Why is it on us to justify our [marginalized students’]presence instead of institutions to justify our absence?” Glazier said. “Stop treating students from marginalized groups as problems, and start treating them as people.”
Press Conference: Stars and Their Activity (by Macy Huston)
Chih-Chun “Dino” Hsu (Northwestern University) kicked off this afternoon’s press conference with the “Discovery of the Shortest-Period Ultracool Dwarf Binary.” Ultracool dwarfs are low-mass stellar/sub-stellar objects with temperatures below 3000K. Binary systems, particularly those with short periods, are important for creating accurate theoretical models. Only three short-period ultracool dwarf binaries were known before this discovery. Keck observations of the LP 413-53 AB system show a radial velocity signal indicating a 20.5-hour orbital period. This pair’s close-in orbit is comparable to the distance between Jupiter and the Galilean moons. It is unlikely that the objects formed this close together. Two more likely scenarios are orbital evolution and scattering caused by an (ultimately ejected) tertiary companion.
Next up was “To Rain or Not to Rain: Correlating Solar Flare Class and Coronal Rain Statistics” from Kara Kniezewski (United States Naval Academy). Magnetic field line reconnection causes solar flares that heat up plasma, causing it to expand then “rain” back down to the surface. The team analyzed 240 solar flares from 2011 to 2019 (Solar Cycle 24) to track post-flare rain occurrence and duration. The data show a correlation between higher flare strength and higher rain occurrence and duration. They also found that these post-flare rains can predict future solar activity. More powerful flares correspond with higher starspot coverage. While this “rain” effect was known to exist for a while, this work finally examined the issue in detail and established the statistics of post-flare rain in the astrophysical literature.
The third presentation came from Marina Kounkel (Vanderbilt University): “Relating Angular Momentum Evolution and Gyrochronology for Young Stars in the Field.” Stellar ages are typically measured in the context of a cluster of stars that formed together. Based on the population’s evolution, best visualized on an HR diagram, the cluster’s age can be estimated. Gaia has identified thousands of new clusters, allowing for more of this type of study. However, billions of main sequence stars exist in the field, rather than their birth clusters, so we need another method to measure their age. By tracking brightness variability due to starspots, we can measure the rotation periods of stars with telescopes like TESS. With mass and radius data, in addition to period measurements, angular momentum can be estimated. Angular momentum decreases with stellar age, which allows these “gyrochronology” measurements to predict the ages of field stars. This project produced an empirical grid for gyrochronology based on TESS data.
Next, Anastasios Tzanidakis (University of Washington) presented the “Discovery of the Deepest and Longest Known Blinking Giant Star Gaia17bpp.” (Press release) The star’s interesting activity was detected with Gaia, which measures the position and brightness of millions of stars in the galaxy. The cool M-giant star was notable for its odd optical light curve, where it gradually brightened ~4 magnitudes over ~3 years. Archival data back to the 1950s showed a relatively flat light curve for the star until 2013, when it very gradually dimmed. This dramatic dimming event may be explained by a dusty disk eclipsing it, where the disk may host a hot star in its center. If the two stars are gravitationally bound, the orbital period should be ~100–1000 years, so these eclipse events are very rare. This calls back to a similar system, Epsilon Aurigae, which shows dramatic 2-year eclipses every 27 years. These two systems (along with two others) belong to an emerging population of binary stars with dramatic dimming events which future surveys like LSST should help characterize.
The final presentation of this session was “Starspots and Magnetism: Testing the Activity Paradigm in the Pleiades and Messier 67 Star Clusters” from Lyra Cao (The Ohio State University). Cool stars show a lot of magnetic activity and starspots, which can affect their interior structure. In order to create accurate models of these stars, magnetism has to be accounted for. The team developed a method to directly measure the magnetism of stars by separating out the ambient surface and the starspot signatures in their spectra. This allows for magnetic studies in open clusters, where stars all have similar ages and compositions. Rapidly rotating stars show stronger magnetism and starspot coverage, but at a high enough speed, this effect saturates, and starspot levels remain flat. The team found some anomalous stars whose starspot coverage appears too high for their relatively slow rotation periods. When modeling eclipsing binary stars, their radii can appear inflated compared to real radius values. Accounting for starspots can allow for more accurate radius and temperature estimates, which also enables more accurate radius measurements for transiting planets. Starspot activity is most powerful for low-mass stars and stars turning off of the main sequence, then fades away in the stellar evolution process as stars dramatically expand and slow their rotation.
Henry Norris Russell Lecture: Richard Mushotzky (University of Maryland) (by Graham Doskoch)
The Henry Norris Russell Lectureship is presented to an astronomer who has distinguished themself throughout the course of their scientific career. This year’s recipient was Prof. Richard Mushotzky, of the University of Maryland, whose career has paralleled the course of the field he has dedicated his life to: X-ray astronomy. He has seen everything from its serendipitous arrival and exciting early years to the earliest X-ray observatories to the leaps and bounds achieved by the Chandra and XMM-Newton missions. Prof. Mushotzky summarizes where the field is right now as we move into an age of X-ray astronomy heralded by several new instruments.
He began his talk by taking us back to the early days of X-ray astronomy with the launch of the Uhuru satellite. Its X-ray observations gave astronomers a new toy in their toolkit to study active galactic nuclei (AGN), supermassive black holes which are accreting matter and spewing out relativistic jets, high-energy emission, and more. When Uhuru was launched in 1970, AGN were still poorly understood; while we know much more about them today, plenty of questions remain. How are the different kinds of AGN related? How do they interact with their host galaxies? How common are they?
More progress on these problems was made with the HEAO program in the late ‘70s and early ‘80s, which Prof. Mushotzky worked on after finishing graduate school. The HEAO missions studied, among other things, the variability of AGN and were also able to take — in Prof. Mushotzky’s words — “boring” spectra. More progress was made on the spectroscopic front towards the end of the century when Chandra and XMM-Newton launched; over the past couple decades, they have remained stalwarts of the field.
Prof. Mushotzky turned to some of today’s state-of-the-art X-ray astronomy, focusing on the work he and his colleagues have done recently on AGN, much of which has been enabled by the Swift Observatory’s Burst Alert Telescope (BAT). Some of his work has involved studying emission from what are called radio-quiet AGN – many of which can, nevertheless, be detected with radio telescopes like ALMA. Their observations at high frequencies (for radio waves, at least) showed an unexplained component of AGN spectra not easily attributed to known high-energy processes.
They also noticed interesting relationships between active supermassive black holes and their host galaxies. A galaxy is more likely to host an AGN if it contains more molecular gas; conversely, it also turns out that galaxies with AGN are more likely to have large molecular gas reserves. Prof. Mushotzky and collaborators also found that AGN hosts tend to have undergone more mergers with other galaxies; he showed the mosaic below as an example of how spectacular these mergers can be.
Merger remnants, some of which host AGN. [Koss et al. 2010]
The final section of Prof. Mushotzky’s lecture was dedicated to what the future holds for X-ray astronomy. Two major missions headline the decades to come. This May, the XRISM mission will be launched, equipped with imaging and spectroscopic instruments to study soft x-ray emission. It will be followed in 2032 by the AXIS satellite, which will be roughly 10 times as sensitive as Chandra. AXIS will address many of the priorities of x-ray astronomy determined by the Astro2020 decadal survey — truly a telescope for the 21st century.
HEAD Bruno Rossi Prize Lecture: Keith Gendreau and Zaven Arzoumanian (NASA Goddard Space Flight Center) (by Ryan Golant)
Each year, the Bruno Rossi Prize is awarded for “a significant contribution to High Energy Astrophysics, with particular emphasis on recent, original work.” This year, the Rossi Prize was given to Keith Gendreau, Zaven Arzoumanian, and the team responsible for the Neutron Star Interior Composition Explorer (NICER), a revolutionary X-ray telescope launched in 2017. In this plenary lecture, Dr. Gendreau and Dr. Arzoumanian summarized NICER’s capabilities and goals and provided a glimpse into the deluge of fascinating results emerging from NICER’s data.
Dr. Gendreau opened the talk by thanking the whole NICER team, including the nearly 100 scientists in the science working group; later in the talk, Dr. Arzoumanian expressed similar gratitude, stating that “it’s a privilege everyday to work with the talented people who work with NICER.”
Dr. Gendreau’s portion of the talk largely focused on NICER’s unique design specifications. All of NICER’s optics are contained within a small box of roughly one cubic meter, deemed the X-ray Timing Instrument (XTI); the XTI contains 56 densely-arranged concentrator mirrors and sunshades, focusing X-ray emission onto an array of 56 detectors. Since NICER’s original goal was to observe point sources like neutron stars — and not to produce large-area images — the telescope’s instrumentation sacrifices field of view in favor of high throughput and mobility, collecting as many X-ray photons as possible; the XTI can detect individual photons with an energy resolution on par with the best CCD detectors and a time resolution of less than 100 nanoseconds. The XTI is also attached to a highly flexible mount, allowing the instrument to slew quickly and precisely to capture a target’s position down to an arcminute or better.
A detailed schematic diagram of NICER. [Slide by Keith Gendreau]
A view of the Neutron star Interior Composition Explorer (NICER), seen at the center of this image, in its berth on the International Space Station. [NASA]
NICER is installed on the International Space Station (ISS) and remains the largest producer of peer-reviewed papers of any experiment on the ISS. While the space station presents a number of large obstructions to NICER’s view (including solar panels located a foot away from the XTI box), this is not a problem for NICER, which is constantly slewing and bouncing back-and-forth between targets to minimize obscuration. In a fun turn of fate, NICER was sent up to the ISS on the 100th rocket to be launched from Pad 39A at the Kennedy Space Center, the same pad that launched the first humans to the moon.
After reviewing NICER’s key capabilities, Dr. Gendreau passed the mic to Dr. Arzoumanian to talk about NICER’s science results. The initial goal of NICER was to probe the structure, dynamics, and energetics of neutron stars — “the most outrageous objects most people have never heard of.” We currently don’t have a clear picture of what goes on within a neutron star, since the extremely high densities (twice the density of an atomic nucleus) yield matter with exotic properties. However, by measuring the masses and radii of neutron stars (which turns out to be a formidable challenge), one can make inferences regarding the interior composition — stiff cores generally result in larger stars, while fluid cores give smaller stars. By carefully analyzing the X-ray pulses emitted by the millisecond pulsars PSR J0030+0451 and PSR J0740+6620, the NICER team was able to obtain reliable masses and radii for these two neutron stars, thus placing unprecedented constraints on neutron star interiors — favoring a stiff core. Upon the release of NICER’s data on PSR J0030+0451, Nature published an article declaring that “the golden age of neutron-star physics [had]arrived”; with more neutron star measurements on the horizon, NICER should continue to revolutionize our understanding of these compact objects.
Dr. Arzoumanian went on to detail how NICER’s science output has spread far beyond the instrument’s original mission of studying neutron star interiors; through NICER’s vibrant Guest Observer program, the broader astrophysics community has steered NICER towards a wide array of other exotic objects and phenomena. NICER data has “rewritten” the textbook picture of pulsar magnetic fields, definitively illustrating that these fields are more complex than simple dipoles. Additionally, NICER has discovered a new accreting millisecond pulsar in an ultracompact binary system, has traced continuous gravitational wave emission back to rotation-powered and accreting neutron stars, and has placed constraints on the geometry of disks around neutron stars. NICER has also significantly contributed to black hole science: NICER is particularly effective at reverberation mapping — which provides information on black hole structure and mass and illuminates the connection between accretion disks, black hole coronae, and jets — and has solved the mystery behind “changing-look” AGN, accreting black holes with highly variable fluxes. Much of this new science is due to NICER’s scheduling agility and dense monitoring, with NICER carrying out multiple coordinated observations in each ISS orbit.
Dr. Gendreau closed the talk with a brief discussion of NICER’s OHMAN (“On-orbit Hookup of MAXI and NICER”) program. As the name suggests, OHMAN couples NICER to JAXA’s MAXI instrument, another payload on the ISS that’s capable of scanning a huge portion of the sky for X-rays; when MAXI picks up a signal, OHMAN tells NICER to slew immediately towards the source, enabling high-resolution detections of fast transient events. Recently, OHMAN proved invaluable in the study of GRB221009A, the most energetic gamma-ray burst ever detected. Dr. Gendreau concluded by remarking that, with the implementation of OHMAN, NICER has become a dynamic partner in our multi-wavelength and multi-messenger exploration of the universe, well in line with the priorities of the Astro2020 decadal survey.
Editor’s Note: This week we’re at the 241st AAS meeting in Seattle, WA, and online. Along with a team of authors from Astrobites, we will be writing updates on selected events at the meeting and posting each day. Follow along here or at astrobites.com for daily summaries, or follow @astrobites on Twitter for live coverage. The usual posting schedule for AAS Nova will resume on January 18th.
Fred Kavli Plenary Lecture: Jane Rigby (NASA Goddard Space Flight Center) (by Graham Doskoch)
AAS 241 kicked off with one of the most anticipated plenary talks of the week. Dr. Jane Rigby, the Project Scientist for Operations for JWST, has helped shepherd the telescope through many of its crucial milestones, from the tests upon tests upon tests before it even left the ground to the agonizing hours of launch day to the long, arduous process of scientific commissioning. She was chosen to give the Fred Kavli Plenary Lecture in recognition of her work to build and operate what might be the most important telescope of this decade and the next.
Dr. Rigby began by reflecting on the early days of gravitational lensing surveys, and the wealth of information that can be obtained from this phenomenon, including spectra and possibly details on individual stars within lensed galaxies. JWST was expected to significantly improve on previous observations — and it hasn’t stopped there. Its scientific performance has exceeded expectations across the board, from its point spread function, to its guiding and pointing accuracy, to its sensitivity to background light and stray photons. Over 20,000 people were involved in the telescope’s design, construction, deployment or operation in some way, their work has paid off.
As a brief interlude, Dr. Rigby talked about the human side of this endeavor. She discussed the tense days during and after JWST’s launch, saying, “It’s a lot like having a newborn at home… We didn’t know if the mission was going to be a total failure or if it was going to work.” So many things could have failed, like the unfolding of the solar panels or the deployment of the sunshield.
Fortunately, nothing major failed, and JWST has already produced prodigious amounts of scientific results. Dr. Rigby noted that astronomers have already published 163 papers based on JWST observations — on galaxies alone! In the spectroscopic realm, the telescope has targeted exoplanets, stars and galaxies, probing the cosmos back to a redshift of 13.17 — in other words, when the universe was only a few hundred million years old. The images, too, are phenomenal; she shows a picture of a Wolf-Rayet star in a binary system, which forms concentric circles of dust every eight years.
Before wrapping up her talk, Dr. Rigby took a moment to acknowledge that JWST is “the telescope that 20,000 people built.” That’s what it takes to peer so deep into the cosmos — and the JWST team pulled it off.
View live tweets of this session by Graham Doskoch here.
#AbolishQuals: Barriers to Success for Graduate Students of Color in Astronomy (by Pratik Gandhi)
One of the first special sessions of this year’s AAS was the panel discussion on qualifying exams organized by the Committee on the Status of Minorities in Astronomy (CSMA). Moderated by Dra. Nicole Cabrera Salazar, co-chair of the CSMA, the panel featured PhD students Erin Flowers (Princeton), Caprice Phillips (Ohio State), and Keshawn Ivory (Vanderbilt), along with professors Enrico Ramirez-Ruiz (UCSC) and David Helfand (Columbia).
Quals, or qualifying exams, are a staple in most US-based astronomy PhD programs, and often consist of a written and/or oral exam used to try and predict which students are most likely to complete their PhDs and succeed. The panel’s focus was addressing the following questions:
What is the purpose of quals in astronomy?
What is the effect of quals on marginalized students?
Have the existence, structure, and validity of quals been properly examined?
What are community sentiments about quals?
How do we move forward?
AAS CSMA conducted an informal survey on twitter, with 62 respondents, to gauge people’s thoughts on and experiences with qualifying exams. There was a decent variety of respondents, from professors to students to university staff, and while most of them identified as White, there was representation from a variety of backgrounds/races as well. About half were Cis women, a quarter Cis men, and 16% under the Trans umbrella.
Survey results on PhD qualifying exam. [Slide by Nicole Cabrera Salazar]
As highlighted in the image above, the main survey results showed that the majority of respondents did not have positive attitudes towards quals, with 45.0% indicating a negative attitude and 33.3% neutral. Answers to what respondents perceived as the purpose of quals included “gatekeeping,” “illusion of rigor,” “weeding out,” and “negative perpetuation of tradition.” Since there is no standard way of doing qualifying exams and almost every single department does it differently, there is large inconsistency in student experiences, grades, and outcomes across departments and institutions.
After this initial presentation, the panelists answered questions. The first one was about the structure of the qual at their institution, and these were their responses.
Erin Flowers (Princeton): the qualifying exam was based on the 4 subject courses; panel of 4 faculty members who ask you questions on those courses, with optional additional “fun time” for extra questions.
Caprice Phillips (OSU) took two qualifying exams. At the first one in Texas, Caprice could choose three classes for an oral exam after presenting on research. The second exam at the OSU was more research-focused, with a presentation followed by questions.
Keshawn Ivory (Vanderbilt) will be taking the qual in May! It’s research-based with feedback from a committee on the students’ research proposal, with possible general astrophysics questions related to the research.
Enrico Ramirez-Ruiz (UCSC): three requirements — submit a first-author paper by the end of 2nd year, give a talk to the entire department, and a written exam about core and elective classes. The third requirement was abolished after realizing that it didn’t have the intended learning outcomes.
David Helfand (Columbia): abolished exams a while ago! In their first year, students pick a project, regularly present it to a faculty committee for feedback, and in September of the second year they start a different project and repeat the process. Then they segue into their PhD dissertation.
Next question: how much informed consent is there for the quals in your department? Do students go in knowing what to expect? How transparent is it?
Erin noted that learning about the exam going in happens from older grad students. Once they take their exams, they immediately write down questions to act as a study guide for future students. Faculty did not provide explicit guidelines for the exams during classes!
Caprice said that at OSU there’s a level of transparency, with the professors often indicating potential questions, and you’re allowed to discuss and clarify with faculty.
Keshawn noted that at Vanderbilt, the grad students learnt from more senior grads. This is also common at many other institutions! One hidden component, however, relates to the purpose of the test — to determine whether the student possesses the ability to succeed.
Prof. Ramirez-Ruiz said that UCSC did not have a very transparent exam in the past, but is getting better now. In the past, the written exam did not correlate with metrics for success, and it took a couple of faculty doing that analysis to motivate abolishing it.
Dra. Salazar raised the important point that departments have a responsibility to their students; not just the other way around. Fewer than 1 of 5 PhDs are going to become faculty, so why is there so much of an onus on students to replicate the standardized way of doing academia, instead of training them for a variety of research and other careers? Dra. Salazar also mentioned inertia in psychosocial situations: the idea of abolishing something seems like it’ll never happen because of institutional resistance, so we might never try to actually do it. However, there are institutions that ARE and HAVE BEEN doing it successfully!!!
Audience question: how does your institution treat disabled students going through quals?
Prof. Ramirez-Ruiz said that a lot of the UCSC discussions were triggered because a disabled student had difficulties with the test, which prompted re-evaluation of the exam’s purpose as well as eradicating barriers for students across many dimensions of marginalization/oppression.
Caprice noted that often disability accommodations aren’t genuine, because departments use the extra time students are given to ask them extra questions instead of giving the students more time to think!!! Super important when considering the needs of disabled students.
The conversation started wrapping up with Dra. Salazar highlighted the collective power that graduate students have, pointing to the recent UC-wide strikes as an example. However, the problem is that the onus is usually on the students currently in the program and not on the system!
View live tweets of this session by Pratik Gandhi here.
Press Conference: Eyes on Galaxies with JWST (by Mark Popinchalk)
The first of eight press conferences for AAS 241, which are an opportunity for exciting results to have some additional fan fare. And there is nothing more exciting right now than JWST. The panel of five scientists included Dr. Jeyhan Kartaltepe, Dr. James Rhoads, Dr. Philip Appleton, Dr. Haojing Yan, and Dr. Vivian U, all showing off fascinating new science results using JWST to study galaxies.
What was striking was the diversity of results, thanks to JWST’s wavelength range being in the infrared. This means the observatory is well suited to look at distant high redshift galaxies, which Dr. Kartaltepe used to describe the shape of 850 galaxies at z > 3, Dr. Rhoads used to link modern “green pea” galaxies to ancient young galaxies, and Dr. Yan used to identify 87 candidate galaxies at z > 11. It can also be used to look at incredible structure in nearby modern galaxies, where Dr. Appleton described new theories for the radiation in a shockwave in Stephan’s Quintet, and Dr. U probed the interior structure of NGC 7469, creating the maps of different gas species around the super massive blackhole.
Also worth pointing out that running the press conferences this week are Dr. Kerry Hensley, Ben Cassese, and Zili Shen — all current or past astrobiters being the voice of the society!
You can view live tweets of this session by Mark Popinchalk here.
For the second plenary lecture of the week, Dr. Jessie Christiansen presented “Towards an Exoplanet Demographics Ladder: The Emerging Picture of Planet Populations!” Astrobites interviewed her in this article, and Macy Huston wrote our Twitter thread of this plenary talk.
Dr. Christiansen is the Project Scientist for the NASA Exoplanet Archive. She started with an intro to IPAC, the Science & Data Center for Astrophysics & Planetary Sciences at Caltech. IPAC hosts the NASA Exoplanet Archive, which reached the amazing milestone of 5,000 confirmed exoplanets last year!
The next portion of the lecture covered the populations of known exoplanets discovered with each of the four main methods (from most to fewest found): transits, radial velocity, microlensing, and direct imaging. The transit method is great for finding planets on close-in (<1 au) orbits, and we see an interesting split into two populations, with a gap near ~30 Earth masses. The radial velocity method primarily finds planets that are relatively high-mass and on short to intermediate orbits. Microlensing can detect planets across the planetary mass range and within a ~1–10-au orbital range. Direct imaging is only possible for very high-mass and wide-orbit planets. So, how do we bring these all together to get a full picture of exoplanet demographics?
A plot of mass, orbital semimajor axis, and discovery method for known exoplanets. [Slide by Jessie Christiansen]
Dr. Christiansen discussed the prevalence of Earth-like planets, quantified as η⊕. Based on the Kepler planet sample, initial estimates of η⊕ varied by orders of magnitude. With more recent analysis, η⊕ is thought to be in the 10-50% range, but the current estimates are consistent with anything from 1 to 100%. Ongoing refinements of Kepler occurrence rates may help narrow this estimate. Additionally, new exoplanet discoveries from the upcoming Roman Space Telescope and the proposed EarthFinder and Earth 2.0 missions can provide new data sets for this type of analysis.
There are many different types of stars and planetary systems in the Galaxy, so the conditions for planet formation and evolution could impact planetary demographics. Some evidence suggests that Earth-like planets might be more likely to exist in systems that have inner rocky planets and/or outer Jupiter-like planets. Already-discovered systems with planets like these may make good targets for future habitable planet searches. M dwarfs, the most common type of star, may also be potentially habitable host stars.
K2 and TESS are currently enabling the study of small, short-period exoplanets. Dr. Christiansen’s group recently cataloged ~750 K2 planet candidates ready for demographic study, and validated 60. Kepler and K2 populations both show a bimodality in the size distribution of small planets at short periods. Recent M-dwarf studies suggest the existence of a density bimodality dividing rocky planets and water-dominated planets.
A number of other factors could impact the occurrence rates of planets around certain stellar types and regions. Kepler and K2 suggest that small, short-period planets are more common among stars that stay closer to the Galactic plane (i.e., in the thin disk, not the thick disk). Stellar properties like metallicity and age may also affect formation, as protoplanetary disks require planet-building material and dissipate over time.
To wrap up the lecture, we return to the plot of known exoplanets discovered via the four main methods, plotted by orbital semi-major axis and mass (or mass*sin[i]). But, these masses are indirect estimates for all methods. Additionally, different methods focus on different types of host stars. So, combining the data sets is complicated, but not hopeless! There is overlap between the parameter spaces covered. Dr Christiansen proposes the “planet demographics ladder,” as an analogy to the cosmological distance ladder, to bring the methods together where they overlap. Roman’s survey of the Galactic bulge will greatly extend our coverage of planets on orbits around and beyond an astronomical unit, which will work together with Kepler data to establish occurrence rates including η⊕.
Press Conference: Mergers, Bursts & Jets (by Ryan Golant)
The second press conference of AAS241 featured four speakers: Dr. Michael Koss of Eureka Scientific, Inc., Professor Vikram Ravi of the California Institute of Technology, Professor Cecilia Chirenti of the University of Maryland, and Sirina Prasad of the Harvard/Smithsonian Center for Astrophysics. The four talks covered a range of exotic high-energy phenomena, from merging black holes and neutron stars to fast radio bursts to radio emission around massive stars.
Dr. Koss spoke about the detection of two extremely close active galactic nuclei (AGN) in the galaxy UGC 4211; with a separation of only 750 light-years, these two AGN form the closest dual AGN system yet detected. This discovery was made possible by the combination of data across multiple regions of the electromagnetic spectrum: the bright nuclei were first identified in the near-infrared (using Keck’s impressive adaptive optics), then followed-up by millimeter observations from ALMA and optical observations from MUSE. UGC 4211 is thought to be the intermediate result of two merging galaxies and could thus serve as a valuable prototype for similar mergers of distant active galaxies; currently, the behavior of close-in merging supermassive black holes is poorly understood, but UGC 4211 should provide useful constraints on this process.
Professor Ravi presented the first results from the Deep Synoptic Array (DSA), a new radio telescope at Caltech designed to simultaneously discover and precisely localize fast radio bursts (FRBs). In 2022, DSA discovered 30 FRBs, more than doubling the yield from all other FRB observatories. Furthermore, DSA’s impressive field of view, time resolution, and angular resolution allow it to localize FRBs to one-millionth of square degree on the sky — a localization accuracy roughly 600 times better than that of CHIME, another leading FRB instrument. With its remarkable specs, DSA is seeking both to better understand the origins of FRBs and to use FRBs to study the unseen hot luminous matter around and between galaxies; over 80% of the luminous matter in the nearby Universe is unseen, but the dispersion of radio pulses from FRBs can reveal the spatial distribution of this matter. The first results from DSA have already placed new constraints on the mass of the Milky Way’s circumgalactic medium — these results only used data from one DSA-detected FRB, leaving 29 more FRBs to analyze.
An illustration of two neutron stars approaching a merger. [ESO/L. Calçada]
Professor Chirenti described the discovery of two hypermassive neutron stars in archival gamma-ray burst (GRB) data. As two neutron stars merge, the system first emits a gravitational wave signal and then launches a short, violent GRB. Detailed computer simulations incorporating general relativity suggest that, in the time between the gravitational wave emission and the GRB, a single extreme neutron star can form; this hypermassive neutron star (HMNS) is short-lived, however, collapsing into a black hole in less than a second. Prof. Chirenti and her collaborators looked through data on 700 short GRBs from the BATSE instrument and identified two bursts (GRB 931101B and GRB 910711) that exhibited the quasi-periodic gamma-ray signal indicative of HMNS formation. These HMNSs demonstrate record-breaking characteristics for neutron stars, rotating twice as fast as the fastest pulsars and possessing 20% more mass than the most massive neutron stars. While we can currently only see these HMNSs via gamma rays, the next generation of gravitational wave observatories will be able to detect them via their high-frequency gravitational wave emission. (Side note: huge props to Prof. Chirenti who, in the face of computer audio issues during her talk, sang the gravitational wave and GRB frequency signals of a binary neutron star merger herself!)
Finally, Sirina Prasad discussed how recent ALMA observations have shed new light on the peculiar binary star system MWC 349. MWC 349a is a massive evolved star surrounded by regions of hydrogen recombination line maser emission; recombination line maser emission — which presents strongly at radio wavelengths — occurs when the capture of free electrons by free protons triggers stimulated emission. Previously, the Submillimeter Array (SMA) had observed maser emission in MWC 349’s circumbinary disk and in an hourglass-shaped region around MWC 349a caused by an ionized wind; while these SMA observations provided useful information on the dynamics of the disk and of the rotating and expanding wind, the precision of the study was limited by SMA’s angular resolution. ALMA’s superior angular resolution provided a much clearer picture of MWC 349’s maser emission regions, both confirming the disk dynamics and revealing a previously unobserved jet emerging from MWC 349a; this is the first time a collimated jet has been detected around a massive evolved star, thus raising new questions about the process of jet formation and the degree to which jets can impact binary star systems.
Plenary Lecture: Rich Matsuda (California Association for Research in Astronomy) (by Briley Lewis)
The panelists from the plenary on Mauna Kea stewardship. From left to right: Rich Matsuda, Dr. Noe Noe Wong-Wilson, John Komeiji. [Screenshot of AAS 241 livestream.]
“To do the best Earth-based astronomy requires access to places unpopulated by city lights… in many cases, those places also happen to be the ancestral lands of people who connect their lineage and heritage back to the beginning of their universe there as well,” said Kimura. “That is certainly the case for Mauna Kea.”
The road to the recent climactic conflict surrounding the Thirty Meter Telescope was long, as Wong-Wilson described in the session. At the time of the first telescopes in Hawai’i, local communities were overwhelmed by other changes brought about by colonization, but as early as the 1980s Native Hawaiians began to speak up in dissent. Despite “following the rules” and attending community meetings, filing public comments, and opening court cases, their voices went unheard, leading to the more severe actions of physical roadblocks in 2019.
Eventually, a working group was formed to determine a path forward and bring together the various voices in the debate around Mauna Kea. Although it was received initially with great skepticism, the working group produced useful recommendations that then became law, creating the MKSOA. Matsuda credits four ingredients to the success of the working group: relationship-building between the group members, creating a safe and equitable space for all to share opinions, gaining a deeper understanding of Hawaiian culture, and centering the one thing they all had in common — the Mauna itself.
The MKSOA is still in its early formative stages, and (as any government entity does) it will take time to fully develop. Around 14 billion dollars have been allocated to the MKSOA, and they will take the next five years to hire staff and get up and running. After that, it is their responsibility to create plans for the future of astronomy on Mauna Kea, for environmental conservation efforts on the mountain, and more. “Our overall purpose is to manage the mountain and try to understand how mutual stewardship actually happens,” said Komeiji.
All three panelists agreed on the deep importance of the task of caring for Mauna Kea, which is not only important for astronomy but also for defining the culture of Hawai’i in future years. “We are going to be the generation that could finally come together and figure out how to take care of our Mauna,” said Wong-Wilson.
“I hope all of you didn’t see this as only a Hawai’i issue, or only an astronomy issue,” added Matsuda. He emphasized that it is a time to think about systems and whether they’re inclusive, equitable, and allowing everyone’s voices to be heard. The working group and subsequent creation of the MKSOA is truly a testament to the power of community-building when the right relations are prioritized, such as the spirit of the Hawaiian Kapu Aloha. Although Matsuda and Wong-Wilson were once seen as polarized opposition in a false dichotomy between science and culture, they have “been able to forge an unbelievable relationship” according to Kimura, praising how the two have come together to create a better future for Hawai’i.
“Out of extreme challenges come opportunities for new ways forward and new relationships,” said Kimura. In the spirit of the MKSOA, she ended the session by encouraging everyone to build relationships with those who have differing opinions — and with the land they are on.
You can view live tweets of this session by Briley Lewis here.
Newton Lacey Pierce Prize Lecture: Erin Kara (MIT) (by Graham Doskoch)
How do you study the environment around supermassive black holes (SMBHs for short)? These gargantuan beasties may be massive, but when viewed from millions of light-years away, they look small and dim. Fortunately, there’s a way around this — and that was the focus of the plenary talk given by Prof. Erin Kara, the recipient of the Newton Lacey Pierce Prize.
Prof. Kara took us through two intertwined journeys: one personal, one scientific, with valuable lessons from both. Her path through astronomy began as an undergraduate at Barnard College, where she took a physics class taught by Prof. Reshmi Mukherjee and fell in love with the cosmos. She also learned a valuable lesson: always find a good mentor. Prof. Mukherjee certainly was, and Kara soon found herself entering graduate school.
Around the same time, astronomers were making big strides in the study of a subset of supermassive black holes called active galactic nuclei, or AGN. These are SMBHs which are accreting matter; as that matter falls into the black hole, its gravitational potential energy is used to power relativistic jets or is transformed into high-energy X-rays. AGN are more luminous than quiescent SMBHs and can be detected at a variety of wavelengths, but traditional methods couldn’t reach the minute scales needed to probe their inner depths.
Fortunately, astronomers developed a way around this problem with a technique called reverberation mapping. Some of the x-rays created by infalling matter will be “echoed” off the accretion disk, which gives us information about the disk’s structure. Prof. Kara used a more down-to-Earth analogy: audience members could hear sound waves traveling directly from her mouth to their ears, but they could also hear echoes from her as other sound waves bounced off the walls. If someone precisely measured the arrival times of these echoes and calculated the speed of sound, they could determine the shape and size of the room they were in.
Reverberation mapping isn’t quite that simple — but then again, research rarely is. This was the second lesson Prof. Kara shared, the one she learned as a graduate student: every research project ebbs and flows, with periods of stagnation and periods of productivity. The secret to success is having people around you who will support you when you hit those walls.
Taking advantage of the information gathered by reverberation mapping requires adjustments and corrections. For example, AGN exhibit random, stochastic variability, which can drown out the light echoes. Astronomers can get around this by Fourier transforming the data and searching for signals that travel on different timescales than the stochastic variations; these are signals of the echoes. They also have to take into account relativistic effects, from both the intense gravitational pull of the black hole and the fast-moving matter in the accretion disk.
AGN aren’t the only objects that can be studied using reverberation mapping. Other promising targets include tidal disruption events and even stellar-mass black holes in binary systems. The latter group of objects can emit X-rays if their companion is a normal star; astronomers refer to these systems as X-ray binaries. They’re interesting because they undergo outbursts, but on timescales of only months to a year. This makes them potential analogs for AGN, which can evolve similarly but on much longer timescales.
As another interlude, Prof. Kara discussed a third lesson, from her time as a postdoc: branch out in your research, and work with new collaborators. Reverberation mapping is being applied to new types of objects and is yielding exciting new results; the same can be true for any astronomer poking their nose into a new subfield.
The study of X-ray binaries has been aided by NICER, on the International Space Station. Prof. Kara described some work that has been enabled by NICER, led by Kingyi Wang, a PhD student at MIT. Wang created a pipeline to study X-ray binaries and track them over the course of an outburst. Her results show that as the emission changes throughout an outburst, the lag times of light echoes can increase by an entire order of magnitude — so something in the X-ray binary is physically changing size by quite a lot! One possible culprit could be the relativistic jets given off by the accreting black hole.
Prof. Kara gave one final bit of advice, this time from her years as a professor: “Don’t forget about your hobbies!” Astronomers are human beings, not machines; we need rest and relaxation and time away from our work.
Prof. Kara closed the talk by showing some examples of sonification applied to AGN. Sonification is a method of turning images into sounds, making them accessible to visually impaired folks without losing any of the information. She showed several model AGN echoes and their sonified counterparts, joking, “You can hear the general relativity in these simulations!” She was right — and it was spectacular.
Prof. Kara spoke to Astrobites about her experience and you can read the post here.
You can view live tweets of this session by Graham Doskoch here.
Judging by the hundreds of papers about data from its first months of observations, astronomers can’t get enough of JWST. Appropriately enough, then, we both began and ended the day with sessions about the telescope and its results. To complement the morning’s plenary lecture by Dr. Jane Rigby, the evening brought us the JWST Town Hall, a set of short talks describing the mission, the telescope’s performance so far, and the resources available to astronomers using it.
Bridget Samuelson, of Northrop Grumman, opened the session with a brief welcome and a reminder of the public recognition JWST has already achieved. Northrop Grumman is one of the leading contractors on the telescope’s design and fabrication, and Samuelson has played several roles during the odyssey to send it to space. She noted that excitement about JWST hasn’t worn off — in fact, the team was just awarded the Goddard Memorial Trophy.
Next to take the podium was Dr. Nancy A. Levenson, who is currently serving as the Interim Director of the Space Telescope Science Institute (STScI). She showed some of the most famous early images from JWST: iridescent nebulae, mind boggling spectra, and deep galaxy fields. Dr. Levenson gave a brief overview of the role STScI plays for JWST. It’s the Missions Operations Center for the telescope, and handles proposals, data collection, communication with observers, and much more. She also drew attention to the JWST Users Committee (JSTUC), which provides a voice for the astronomers using the telescope.
Dr. Levenson was followed by Dr. Jonathan Gardner, of Goddard Space Flight Center, who gave updates on improvements since the telescope’s launch. After a notable micrometeoroid impact in May 2022, the team decided to implement a micrometeoroid avoidance zone in the next observing cycle. In August, an increase in friction was noticed in one of the grating wheels of the Mid-Infrared Instrument (MIRI), leading the team to pause one particular MIRI observing mode until November while the cause was investigated. Dr. Gardner also noted that the telescope briefly went into safe mode in December after a software problem hit the attitude control system, but was brought back online within a couple days, with minimal disruption to science operations.
Dr. Gardner finished by walking through some of the science highlights since observing began last year, including the highest-redshift images taken to date, wonderful exoplanet spectra, and observations of barred spiral galaxies only a few billion years after the Big Bang. Judging by JWST’s images showing up everywhere from Times Square to a Coldplay concert, the public might be almost as excited by the results as the astronomers who found them.
The next speaker was Dr. Jane Rigby, the Project Scientist for Operations for JWST, who had given the Fred Kavli Plenary Lecture that morning on the telescope’s science performance. In her Town Hall segment, she shared similar information, noting that JWST has exceeded expectations in many of its performance metrics. She highlighted how the smooth mirrors have enabled exceptional sensitivity, and the telescope’s pointing and guiding abilities have far exceeded what was required. The micrometeoroid impact was worrisome, but as Dr. Gardner mentioned, measures are being taken to avoid repeat events. Dr. Rigby noted that with two decades worth of fuel, nobody knows what will eventually limit JWST’s operating lifetime — but it will be sticking around for a while.
Dr. Rigby was followed by Dr. Klaus Pontoppidan, who described the work of the Science and Operations Center during Cycle 1 observations. The Center performs a variety of tasks, including coordinating observations, supporting proposal calls for Cycle 2, public outreach, and more. It also continues to improve the automatic calibration pipeline that processes the data, as well as the many tools available to astronomers using JWST or working on proposals.
To give a view of the mission timeline, the next speaker was Dr. Christine Chen, representing the JWST Science Policy Group at STScI. She reminded everyone that the call for Cycle 2 proposals is out, with the submission deadline of January 27 approaching. Over 5,000 hours will be available for General Observer Programs, with additional time set aside for parallel, survey or archive programs and JWST Joint Programs with other telescopes, like ALMA or the Hubble Space Telescope. PIs will be notified of decisions in May, and Cycle 2 itself will start in July. Looking further ahead, the call for Cycle 3 proposals will be officially made on August 15, with a deadline of October 27, and Cycle 3 will begin in July of 2024.
As if to inspire the audience to finish any proposals by January 27, Dr. Chen was followed by Dr. Amaya Moro-Martín, who described some of the science highlights from the Early Release Science (ERS) programs. These teams were responsible for some of the first JWST results this past summer, and include the CEERS, TEMPLATE and Q3D groups. Over 175 papers have appeared on arXiv in the 6 months since science observations began, and ERS programs deserve a lot of credit for these early strides.
The session finished with a brief overview of how JWST press releases work. Teams using JWST data who believe they have a significant result can submit their results to STScI, which will make a determination. If the research seems to warrant a press release, STScI will create text and visuals, which will then be reviewed by the team and by NASA. The overarching lesson is to talk to the STScI team sooner rather than later, to give them adequate time to work on a release before a paper is published.
You can view live tweets of this session by Graham Doskoch here.
This week, AAS Nova and Astrobites are attending the American Astronomical Society (AAS) winter meeting in Seattle, WA, and online.
AAS Nova Editor Kerry Hensley and AAS Media Fellow Ben Cassese will join Astrobites Media Intern Zili Shen and Astrobiters Macy Huston, Briley Lewis, Yoni Brande, Pratik Gandhi, Graham Doskoch, Mark Popinchalk, Ali Crisp, Isabella Trierweiler, and Ryan Golant to live-blog the meeting for all those who aren’t attending or can’t make all the sessions they’d like. We plan to cover all of the plenaries and press conferences, so follow along here on aasnova.org or on astrobites.org! You can also follow @astrobites on Twitter for the latest updates.
Where can you find us during the meeting? We’ll be at the Astrobites booth in the Exhibit Hall all week — stop by and say hello! In addition, you can catch Kerry, Ben, and Zili at the press conferences all week.
You can also catch us at several sessions throughout the meeting:
Astrobiter Briley Lewis will give a talk during the Resources and Education Research for Introductory Astronomy Courses session titled “Effects of Popular Science Writing Instruction on General Education Student Attitudes Towards Science: A Case Study in Astronomy” on Monday, January 9, from 10:20 to 10:30 am PT (program number 115.03). Briley will also speak during the ExoExplorers special session titled “Early-Career Perspectives on the Intersection of Exoplanet Science and DEIA in Astronomy” on Tuesday, January 10, from 2:45 to 3:00 pm PT (program number 255.04). Briley’s talk, “Considering Disability and Accessibility in Astronomy,” will describe “challenges faced specifically by disabled astronomers in our field, share personal experiences with accessibility and creating accessible events (e.g., planetarium shows accessible to blind and d/Deaf audiences), highlight the work of leaders in accessibility in astronomy, and make recommendations for how you can contribute to accessibility.”
AAS 241 is nearly here! The AAS Publishing team looks forward to connecting with meeting attendees in Seattle, WA, and online, and we’re excited to share a preview of upcoming publishing-related events. Also, be sure to stop by the AAS booth in the Exhibit Hall, which will be staffed by several members of the publishing team, including Julie Steffen (AAS Chief Publishing Officer), Ethan Vishniac (AAS Journals Editor in Chief), Frank Timmes (AAS Journals Associate Editor in Chief), and AAS Journals Data Editors Greg Schwarz and Gus Muench. At the booth, you can test drive the augmented reality experience newly added to the AAS journals (and get your very own augmented reality Merge Cube!) and learn more about the upcoming AAS journals peer review workshop, which will take place in February.
AAS Nova Editor Kerry Hensley, AAS Media Fellow Ben Cassese, Astrobites Media Intern Zili Shen, and the rest of the Astrobites team will also be available at the Astrobites booth in the Exhibit Hall.
AAS Production at IOPP: Workflow, Language Editing, and the AAS Style Guide
Tuesday, January 10, 10:00 am PT | iPoster Theater
Concision and clarity are essential to ensuring that your research is meaningful and understandable to the American Astronomical Society (AAS) community. Senior members of the AAS production team explain in this session how Institute of Physics Publishing (IOPP) assists in that mission with publishing and editing expertise. We will focus on the centrality of the AAS Style Guide in achieving that clarity required in your scientific discipline and on how the Language Edit team at IOPP helps you apply the principles of AAS style most effectively.
Keywords and Descriptive Metadata in Astronomy
Over the years, there have been many efforts to codify and create lists of relevant keywords for the astronomy community. In the early days, these vocabulary lists were just that, alphabetical lists of astronomy terms, sometimes arranged into a shallow hierarchy. The most recent effort along these lines is the Unified Astronomy Thesaurus (UAT), which adds a deep hierarchy to organize and define relationships between astronomical concepts, as well as being built using modern technology standards that allow it to integrate with online platforms and services.
The real strength of the UAT is its open call for community feedback. Like all scientific fields, the astronomy community is made up of a diverse group of experts, including both researchers who specialize in narrow fields and those who have a broad understanding of general astronomy. Drawing upon those experts to influence the content and direction of the UAT is what keeps the project relevant and useful as it sees wider adoption.
Stop by the American Astronomical Society (AAS) booth during the morning coffee breaks to catch up with Katie Frey, Curator of the Unified Astronomy Thesaurus. Learn about how the UAT has been implemented by institutions such as the AAS, the Publications of the Astronomical Society of the Pacific, and the Space Telescope Science Institute. Explore the concepts, structure, and hierarchy of the UAT. Do you have any feedback about the UAT? Katie would love to hear it!
Where to find the UAT at AAS 241:
Monday, January 9th
Tuesday, January 10th
AAS booth (#627)
9:00 – 10:30 am
AAS booth (#627)
9:00 – 10:30 am
CfA booth (#431)
1:30 – 6:30 pm
CfA booth (#431)
10:30 am – 1:30 pm
AAS booth (#627)
5:30 – 6:30 pm
Wednesday, January 11th
Thursday, January 12th
AAS booth (#627)
9:00 – 10:30 am
AAS booth (#627)
9:00 – 10:30 am
CfA booth (#431)
12:00 – 2:00 pm
AAS booth (#627)
5:30 – 6:30 pm
AAS booth (#627)
5:30 – 6:30 pm
NOIRLab Legacy Mosaic Data Rescue Project
Sunday, January 8, 4:15–4:30 pm PT | Seattle Convention Center, Room 614
AAS Archive Fellow Nick Foo and AAS Chief Publishing Officer Julie Steffen will present on a collaborative project being carried out by the AAS and NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab) to conduct a rescue project on the legacy mosaic data archived by the National Optical Astronomy Observatory (NOAO; National Optical Astronomy Observatories pre-FY2000). In the mid-1990s, telescopes at Kitt Peak National Observatory (KPNO) and Cerro Tololo Inter-American Observatory (CTIO) made the significant transition to archiving digital observational data stored on magnetic exabyte tapes. From 1993 until 2004 5+ million raw data files on 9,000+ unique data magnetic tapes were collected in the NOAO Science Archive. In the present day, the 8-mm tape format is obsolete, and the data have been offline for the past 20–30 years despite numerous possibilities for archival research. Eventually, they will not be recoverable because the tapes will degrade over time, and the hardware that is required will no longer be available. Using a bank of 8-mm tape readers, the recovery project team has managed to extract and catalog the data. So far, nearly all Mosaic-1 wide-field images have been recovered. Currently, existing pipeline software is being developed to perform calibration and basic analysis to produce science-ready images. All observations recovered from the project will be publicly accessible via the Astro Data Archive ingest. Hopefully, the unveiling of previously dark data will initiate and inspire numerous archival research investigations in the future.
Editor’s Note: This week we’ll be writing updates on selected events at the 54th Division for Planetary Sciences meeting in London, Ontario, and online. This post covers the last three days of the meeting. The usual posting schedule for AAS Nova will resume on October 10th.
Planetary Atmospheres and the Search for Signs of Life Beyond Earth (Sara Seager)
Just 30 years ago, exoplanets were a wild and unpromising idea. Even when the first transiting exoplanet was discovered in 1999, many researchers thought the field wouldn’t go anywhere; sure, exoplanets exist, but the measurements are just too hard to make. In the first of today’s plenary talks, Sara Seager (Massachusetts Institute of Technology) reminded the audience that the line between what is accepted and what is dismissed is constantly changing, and ideas that seem outlandish may someday advance our understanding.
Seager’s talk focused on the search for life on worlds outside our solar system, especially the concept of biosignatures: chemical compounds in the atmosphere of a planet that indicate that life is present. While detecting life in this way sounds simple, Seager delineated the many reasons that it’s not. Part of the issue is our observational constraints, which push us to search for life-bearing planets around the smallest stars, M dwarfs, in search of a strong signal. M dwarfs are far more active and variable than the Sun, which spells trouble for the observational side of the issue (variability can drown out subtle atmospheric signals) as well as the biological side — during an M dwarf’s lengthy “teenage” phase, its extreme thermal output might doom any life that arises on nearby planets.
An explanation of the main objections to the discovery of phosphine in Venus’s atmosphere. Click to enlarge. [Slide by Sara Seager]
And claiming detection of a biosignature gas is just the beginning: in 2020, a team led by Jane Greaves announced the detection of a radio transition of phosphine, a gas produced by life on Earth, and controversy ensued. Some research groups cast doubt on the presence of the phosphine line, and others acknowledged its presence but attributed it to a less exciting gas, sulfur dioxide. The question of whether phosphine is an indisputable biosignature at all loomed over the technical debate. While further work by Greaves and collaborators, including Seager, presented new corroborating observations from the James Clerk Maxwell Telescope and archival observations from the Pioneer Venus mission, investigated the sulfur dioxide possibility and found it unlikely, and presented evidence against non-biological origins for phosphine on Venus, the debate continues.
This process shows that science is working, Seager notes, and the back and forth incited by the potential discovery of a biosignature gas in our planetary backyard will likely play out for years to come. And we know far more about Venus than we do about any exoplanet — imagine the debate that would follow the first detection of phosphine on an exoplanet! (As an aside, Seager noted that phosphine is hardly the most outlandish Venus-related proposal — major depletion of sulfur dioxide in Venus’s atmosphere could be explained by ammonia-producing life that partially neutralizes the sulfuric acid within the clouds. A tidy explanation, or optimistic humans connecting unrelated data points? It’s up for debate!)
Seager concluded with a bevvy of tantalizing (or unpromising, depending on your opinion!) possibilities: Breakthrough Starshot would send thousands of miniature spacecraft on a life-finding mission; a solar gravitational lens telescope would boost our technological capabilities; and an Earth-like planet orbiting a white dwarf would give us a chance to detect gases associated with technological processes, like sulfur hexafluoride. The possibilities are wild and endless — buckle up for a decades-long search for life beyond Earth!
A Unique Origins Survey: Gaia-Enabled Occultation Measurements of Small Bodies in the Outer Solar System (Marc Buie)
In order to understand the origins of our solar system, we need to understand the small bodies of the outer solar system. So says Marc Buie (Southwest Research Institute), who chases outer solar system bodies from Earth by watching them block the light from distant stars. Part of the challenge of studying these far-flung objects is that you need to study a lot of them to make firm conclusions, so chasing down individual objects with an expensive spacecraft, à la New Horizons’s pursuit of Pluto and Kuiper belt object Arrokoth, is infeasible. Instead, ground-based efforts with telescopes of modest size can play an important role.
The New Horizons mission is a source of inspiration for Buie; tracking down Arrokoth prompted scientists to devise new analysis techniques and ways of processing data, and observations of the curious contact binary forced researchers to rethink theories of how objects in the outer solar system formed. Since researchers observed Arrokoth from the ground via a stellar occultation — watching as it blocked the light from a star — before New Horizons encountered it, Buie hopes that linking the ground-based observations to the space-based observations will help us draw better conclusions from ground-based observations of other outer solar system objects.
Using data from the Gaia spacecraft, which has made exceptionally precise measurements of the positions and motions of stars in the Milky Way, Buie anticipates being able to study large numbers of outer solar system objects using stellar occultations. This technique has already allowed us to detect 10-km-scale surface features on the five asteroid targets of the Lucy mission, and it should allow us to constrain collisional processing and cratering of outer solar system objects without sending a spacecraft to them. Multiple possibilities exist for implementing this kind of program, including a fixed robotic array of thirty 28-cm telescopes or a mobile array of small telescopes transported worldwide by trained observers.
While the price tag for implementation might seem large — Buie estimates that observing ten 20-km Kuiper belt objects would require $7 million to cover equipment, travel, and personnel costs — it’s far cheaper than a spacecraft mission. Buie points out that rather than a scientific or technological stumbling block, the issue is a programmatic one; while funding exists for small, speculative projects and massive, spaceflight-ready endeavors, there is something of a funding desert in between these two extremes, making what Buie calls “team science” difficult to get started. In the future, Buie hopes that the planetary science community will consider the kinds of team science it wants to pursue in addition to the kinds of spacecraft missions it hopes to launch.
Astrobiology in the Era of Big Data: Leveraging Chemometrics for Prebiotic Chemistry and Planetary Exploration (Laura Rodriguez)
An explanation of where chemometrics fits in relative to other data science and artificial intelligence concepts. Click to enlarge. [Slide by Laura Rodriguez]
Laura Rodriguez (NASA’s Jet Propulsion Laboratory, soon to be at the Lunar and Planetary Institute) puts computers to work to help us find the best places to search for life beyond Earth. Using chemometrics — an umbrella term that encompasses a variety of computing techniques applied to chemical data — Rodriguez studies prebiotic chemistry, or the formation of organic compounds that may lead to the formation of life.
Prebiotic chemistry is often studied as a way to probe the origins of life on Earth, but it’s also important for predicting where else in the solar system we might find life. By delving into the formation of molecules in different sites around the solar system, we can start to understand the conditions necessary for life to evolve as well as evaluate compounds proposed as biosignatures — even large molecules like ATP (an important organic molecule in the human body that helps deliver energy to our cells) can form without life being present.
Planetary science missions, especially those tasked with searching for life, represent the intersection of the study of prebiotic chemistry and machine learning. Spacecraft missions have reached the point where the instruments are able to collect a massive amount of complex data. While it’s possible for a spacecraft to dutifully beam these data back to Earth to be pored over by scientists, this process is slow and energy consuming, especially for spacecraft exploring the icy worlds of the outer solar system. Instead, Rodriguez proposes that spacecraft be given the tools to make the first analysis pass themselves, engaging in preprocessing steps that help them decide what to do next, without human intervention.
A simplified mass spectrum showing the types of compounds detected in the plumes of Enceladus by the Cassini spacecraft. Click to enlarge. [NASA/JPL/SwRI]
As examples of how this might work, Rodriguez introduced three common techniques for studying chemical compounds on other planets: mass spectrometry (an excellent way to search for biosignature gases; the Dragonfly mission to Titan will carry a mass spectrometer), laser-induced breakdown spectroscopy (used by the Mars rovers to analyze soil samples), and Raman spectroscopy. Rodriguez introduced a rapid and flexible algorithm that could be used by spacecraft to preprocess spectroscopic observations. The process starts with slicing a spectrum into small windows without cutting into important features, allowing the algorithm to fit functions to individual windows separately, increasing the chances of a successful fit. This would allow the spacecraft to deconvolve overlapping spectral lines and rapidly analyze a complex spectrum. Rodriguez also developed a way for spacecraft to predict the chemical formulae corresponding to the peaks in a mass spectrum.
Ultimately, chemometrics will benefit many planned and proposed missions such as the Mars Sample Return program, a Europa lander, and a Ceres sample return mission, allowing spacecraft to make the decisions necessary to optimize limited time, energy, and resources.
Behind the Myth of Meritocracy: How STEM Fields Perpetuate Racial and Gender Disparities (Adia Harvey Wingfield)
Adia Wingfield, a professor of sociology from Washington University in St. Louis, described the current state of racial and gender diversity in science, technology, engineering, and math (STEM) fields in the United States, the issues facing scientists and engineers belonging to underrepresented groups, and how organizations can work to improve the representation of these groups.
Comparison of the demographics of the STEM workforce (top) to the demographics of the US population (bottom). Click to enlarge. [Adapted from slides by Adia Wingfield]
First, the current status: in STEM fields, white men are overrepresented, making up 49% of STEM professionals but just 27% of the US population, as are Asian American men and women, making up 14% and 7% of the STEM workforce and 2.6% and 2.9% of the US population, respectively. All other groups are underrepresented to varying degrees. (See the figure to the right for a full breakdown.)
What’s the cause of this disparity? There are several common — and incorrect — assumptions about the causes of workplace disparities: women tend to prioritize family over work; Black and Latino workers aren’t as qualified; it’s hard to recruit these workers, and once they’re recruited they leave for other opportunities; and STEM is a meritocracy where everything is fair and equal, so these disparities are really out of our control.
In reality, there are biases in the hiring process that disproportionately impact workers belonging to underrepresented groups; unspoken norms and organizational culture can create a “chilly” environment for many employees; harassment is pervasive; and tokenism remains an issue. These issues are wide ranging, and some issues affect people belonging to certain groups more than others (e.g., gender and sexual minorities are more likely to face issues with sexual harassment; tokenism is a complex issue, especially for people who are in the majority with respect to gender but in the minority with respect to race).
As academics, we can learn from the techniques used in corporate settings. Targeted recruitment — turning to historically Black colleges and universities and predominantly Latino-serving institutions rather than solely leveraging existing networks — can open up organizations to job candidates who would otherwise not be part of the applicant pool; formal mentoring programs help connect new hires belonging to underrepresented groups to the rest of the organization, and these programs are especially successful when mentors are incentivized to be invested in the success of their mentees; sexual harassment training with a helpful, rather than punitive, focus (e.g., focusing on bystander intervention rather than the legal consequences of harassment) can improve the organizational climate; and diversity task forces that are given the power to enact change and involve people from all levels of an organization can increase the proportion of historically excluded groups at the managerial level. These techniques, which in a five-year survey were shown to increase recruitment and retention of minoritized individuals, are likely applicable to academic institutions as well.
Survey results regarding participation in mission proposals as principal investigator and co-investigator. [From slide by Julie Rathbun]
Julie Rathbun (Planetary Science Institute) introduced the results of a survey regarding diversity, equity, inclusion, and accessibility in planetary science. The survey, which was funded by the Division for Planetary Sciences, was the result of the latest National Academies of Science Planetary Decadal Survey, which was released earlier this year. For the first time ever, the Decadal Survey included a call to assess the state of the planetary science workforce. The survey results showed that women, disabled scientists, and scientists belonging to the LGBTQ+ community were statistically less likely to be involved in planetary science missions. These results indicate that even after navigating the barriers to entering the field — which are higher for members of historically excluded groups — there are further barriers once you get through the door. Press release
A shape model of asteroid 3200 Phaethon derived from stellar occultation observations. [From slide by Sean Marshall]
Sean Marshall (Arecibo Observatory and University of Central Florida) reported on the unusual rotation of the asteroid 3200 Phaethon. Phaethon is the first asteroid to have been discovered in spacecraft data, it’s one of the largest potentially hazardous asteroids (Marshall emphasized that its orbit is well known and it’s not a threat to Earth), and it’s also the parent body that provides the dust for the Geminid meteor shower. Phaethon is also the target of the Japanese Space Agency’s DESTINY+ mission, which is scheduled to launch in 2024 and fly by the asteroid in 2028. Over the course of repeated observations, researchers realized that Phaethon’s rotation rate wasn’t matching up with predictions, suggesting that its rotation rate has changed. Thanks to 32 years of observations, Marshall and collaborators were able to discern a slight increase in the asteroid’s spin rate — equivalent to a 4 millisecond decrease in its rotation period each year — making Phaethon the largest asteroid known to have a changing rotation period. The cause of this change is unknown, and the leading hypotheses (solar radiation, asteroidal activity) have major issues. Hopefully, DESTINY+ will provide some answers!
Questions Convey Us: Our Human Exploration of the Solar System, 1962 to Now (and After) (Emily Lakdawalla)
Freelance science writer and planetary scientist Emily Lakdawalla kicked off the final plenary of DPS 54 with a perspective on the history and future of planetary science. Planetary science was born of the merger of two scientific endeavors: astronomy and geography. Astronomy began with humans peering at the night sky, trying to understand what importance the stars held for us, and asking questions about our origins. Initially a solitary endeavor, early astronomy was limited to those with the money to build expensive telescopes. And while early astronomers sometimes guarded their data jealously, astronomy has evolved into one of the most open of the scientific fields.
Geography, on the other hand, began with large surveys funded by the reigning governments of newly conquered territories. These surveys thus involved large numbers of people working together, and they evolved to incorporate information about natural hazards such as flood or earthquake risks, which was shared publicly in accessible databases. It’s impossible to ignore the checkered history of geography, which played an important role in assessing the value of lands acquired forcefully in the colonial era.
The first map of the Moon created by the US Geological Survey. [USGS]
Astronomy and geography came together in the form of planetary science when the US entered the space race during the Cold War, promising to reach the Moon. The US Geological Survey created the first map of the Moon and participated in training the Apollo astronauts in geological field techniques. Evidence of planetary science as a tool for international relations came in the form of the many Moon rock samples gifted to other countries. But when the Apollo program concluded, the field of planetary science nearly vanished. Luckily, the Voyager and Viking spacecraft had already been launched, and the iconic images returned by these missions bolstered public opinion and revitalized the field.
Lakdawalla commented on the traditions — both positive and negative — that planetary science retains from its forebears, astronomy and geography. The secretive guarding of data remains an issue (Lakdawalla recounted the case of a spacecraft instrument whose calibration method was never written down in order to maintain the relevance of the sole expert who knew the method; those data are now nearly useless), but planetary science has evolved into an incredibly open field; the existence of the arXiv and the Planetary Data System are proof of that fact.
Lakdawalla closed with some notes of caution for our field: as our exploration of the solar system continues, we must be mindful not to follow the exploitative origins of geography as we consider how best to study these worlds without contaminating them; we must be patient when planning ambitious, decades-spanning missions, and be mindful that these missions may not be for us, but for others who will benefit from them in the future; we’ll need to work hard to convey the importance of the moons and small bodies in our solar system now that all of the planets have been visited by at least one spacecraft; and we should seek to combat the colonialistic tendencies of private space exploration by being sure to include everyone in space exploration, especially those who have been traditionally excluded.
It’s not just for astronomy: JWST has already proven its immense worth to the field of planetary science, and more discoveries are sure to come. Eric Smith (NASA Headquarters) gave an overview of the technical challenges of building JWST and how it will impact the field of planetary science. JWST, as most readers likely know, is a feat of engineering, designed to overcome stringent technical challenges imposed by observational goals. The design and construction of the telescope spanned the tenures of six NASA administrators, and JWST benefited greatly from public support during rough patches in the process.
Smith noted that planetary science proposals during Cycle 1 were particularly successful, with the proportion of selected planetary science proposals being larger than the proportion of submitted proposals. Solar system science will use 7% of the observing time during Cycle 1, amounting to 607.5 hours, 25% of which has already been completed. More than a third of the Cycle 1 planetary science proposals have no exclusive use period, which means the data will become publicly available immediately. Exoplanet science makes up 29% of Cycle 1, requiring 2,516.7 observing hours for 96 programs. Smith commented that several of the Cycle 1 proposals were actually archival proposals, perhaps making this the first mission for which archival proposals were selected for data that hadn’t yet been taken!
In the time since JWST settled into its orbit at L2, it’s become clear that the telescope’s performance will exceed expectations. Thanks to an exceptional launch, it didn’t have to spend fuel getting into position and can instead put that fuel toward extending its lifetime — it’s expected to last twice as long as the initial goal. Its sensitivity, pointing stability, moving target tracking, and other factors are also far better than anticipated. And while a strike from a larger than anticipated micrometeroid prompted some panicked headlines, the team is ready to handle those as well; by rearranging the observing programs that do not require the telescope mirror to be pointing in the telescope’s direction of motion, we can limit the impact of these events. JWST has spurred a flurry of scientific activity; Smith estimated that an average of 3–4 JWST-related science papers are published on the arXiv every day — and the mission is just getting started!
A Future Mission to Uranus: Exploration of Five Possible Ocean Worlds and a Bevy of Small Icy Moons (Richard Cartwright)
A classic Voyager 2 photo of Uranus, taken in 1986. [NASA/JPL-Caltech]
Richard Cartwright (SETI Institute) delved into the icy moons orbiting one of the least explored planets in our solar system: Uranus. While the moons of Jupiter and Saturn were illuminated by the Galileo, Juno, and Cassini missions, Uranus’s 27 moons had only the briefest moment in the limelight following a flyby by Voyager 2. Uranus’s moons fall into three categories: ring moons, classical moons, and irregular moons. Voyager 2 gave us a glimpse of the southern hemispheres of Uranus’s five classical moons (Miranda, Ariel, Umbriel, Titania, and Oberon) and the largest of the ring moons, Puck, in addition to revealing 11 new moons. But these Voyager observations prompted far more questions about Uranus’s collection of moons than they answered: How did the moons form? What do their northern hemispheres look like? Do they have residual oceans? What is the charged particle and dust environment around the moons?
Luckily, the most recent Planetary Decadal Survey prioritized an orbiter and probe to Uranus, opening an avenue for us to answer these questions. Cartwright gave an overview of what we know about Uranus’s moons, what we don’t, and how we might design a spacecraft to the Uranian system to get answers.
Uranus’s 13 ring moons form the most compact group of satellites in our solar system. Only Puck has been spatially resolved in previous observations, and we don’t know the ages of these objects or what their surfaces are like. Perhaps most intriguing of the ring moons is the outermost, Mab, which is likely only 6–12 km in diameter and is probably associated with the dusty μ ring. Given the compactness of the system, it’s likely that the moons share material in an interesting way.
A detailed view of the surface of Uranus’s moon Miranda. [JPL]
Of the 5 classical moons, Ariel has the best evidence for cryovolcanism, showing a long groove reminiscent of fissure-style volcanism on Earth. Umbriel has the oldest and darkest surface but sports a bright region that may also be related to cryovolcanic activity. Miranda also has the potential to be active, since some craters look like they’ve been filled in with some material — although other craters, even nearby ones, have not. Miranda also lacks the hemispheric asymmetry in water ice and reddish surface material that the other large moons have. It’s possible that Miranda formed at a different time from the other classical moons. As Cartwright points out, there’s simply so much we don’t know about these moons!
In terms of a potential future mission to the Uranian system, Cartwright recommends an orbiter, which offers the best chance of studying internal oceans and geologic processes on the moons. An ideal suite of instruments would include a magnetometer, cameras (optical and mid-infrared), a near-infrared mapping spectrometer, particle and dust detectors, and an ultraviolet spectrograph. Timing is important, too — launching the mission in time to catch the Jupiter gravity assist window in 2030–2034 would get us to Uranus faster and get this long-awaited science started!
Editor’s Note: This week we’ll be writing updates on selected events at the 54th Division for Planetary Sciences meeting in London, Ontario, and online. This post covers the first two days of the meeting, and a second post on Friday will cover the remainder of the meeting. The usual posting schedule for AAS Nova will resume on October 10th.
Collecting Samples of Mars: The NASA Perseverance Rover’s Role in Mars Sample Return (Chris Herd)
Chris Herd (University of Alberta) kicked off the first plenary session of DPS 54 with an introduction to how the Perseverance rover will contribute to the goals of the Mars Sample Return program, which plans to deliver samples of the Martian surface to Earth in 2033.
Illustration of the path Perseverance has traveled. Click for high-resolution version. [Slide by Chris Herd]
Herd described Perseverance’s journey from its landing site in Jezero Crater to the edge of the Séítah region, which contains impassible rocks and sand dunes. En route, Perseverance made its first attempt at collecting a sample of rock, but the water-weathered rock disintegrated during the coring process, leaving only atmospheric gases inside the sample tube. After collecting a few more samples, the rover backtracked to the landing site and continued onward to an ancient river delta, a region containing sedimentary rocks formed from silt deposited 3.5–4.0 billion years ago. These sandstone samples, Herd noted, should be especially interesting to analyze when returned to Earth.
So far, 14 of Perseverance’s 38 sample tubes have been filled, containing rocks from a wide variety of geologic regions as well as one sample of Mars’s atmosphere. In addition to the sample tubes, the rover carries five “witness tubes” that will allow researchers to assess the amount of contamination within the rover.
Conceptual illustration demonstrating the stages of the Mars Sample Return program. [NASA/JPL-Caltech]
Perseverance will soon journey to a new region to cache the samples it has collected so far before departing the delta region and Jezero Crater entirely. In the next stage of the Mars sample return program, a lander will touch down, collect the cached samples into a small rocket, and launch them into orbit. From there, another spacecraft will capture the samples and send them Earthward.
Understand Space Weathering of Carbonaceous Asteroids Through the Analysis of Hayabusa2 Samples and Experimental Analogs (Michelle Thompson)
Illustration of the main types and effects of space weathering. [Slide by Michelle Thompson]
Michelle Thompson (Purdue University) described how laboratory experiments can help us understand the effects of space weathering — changes to the surface of an airless solar system body by impacts from micrometeorites and solar wind particles. Space weathering typically affects the top few millimeters of a body’s surface, but the effects are far reaching, changing the spectra of these bodies in a way that laboratory experiments can help probe.
Demonstration of how space weathering changes the spectral properties of lunar materials. [Slide by Michelle Thompson]
To demonstrate the effects of space weathering, Thompson compared a spectrum of lunar soil, which is subjected to space weather effects, to one of ground-up lunar rock, which is protected from these effects. The weather-beaten lunar soil is darker, has weaker absorption features, and is more reflective at reddish wavelengths than bluish wavelengths.
By approximating micrometeorite impacts and buffeting by the solar wind in a laboratory context, researchers determined that the two processes can have competing effects; while both processes weaken absorption features, solar wind weathering makes surfaces redder and brighter while micrometeorite impacts make them bluer and darker. Through these laboratory experiments, researchers hope to be able to separate primary effects — those that are due to inherent properties of the sample — from secondary effects, which are due to space weathering.
Photographs of a particle from Ryugu (left) and a section of the Murchison meteorite that has been treated in a lab to approximate the effects of micrometeorite impacts. [Slide by Michelle Thompson]
In December 2020, a capsule containing more than 5 grams of material collected from the surface of the asteroid Ryugu crashed down in Australia. An analysis of just one particle from this sample revealed a surface pitted and melted by micrometeorite impacts and never-before-seen teardrop- and lentil-shaped nanoparticles, which indicated a flow in the melted region. The next major sample-return event will be the arrival of a sample of asteroid Bennu’s surface in 2023.
From Apollo to Artemis and Beyond: How the Apollo Next Generation Sample Analysis (ANGSA) Program Helps to Prepare for Future Sample Missions to the Moon and Beyond (Juliane Gross)
The Apollo samples underpin much of our knowledge of the Moon as well as other solar system bodies. Click to enlarge. [Slide by Juliane Gross]
Juliane Gross (Rutgers University) described the decades-spanning effort to study samples returned during the Apollo missions. These samples underpin much of our understanding of the Moon as well as other objects in the solar system; researchers use Apollo samples to calibrate remote-sensing data, calibrate the crater-counting curve used for nearly all planetary bodies, identify lunar meteorites that fall to Earth, and understand the space environment surrounding the Moon throughout different periods in solar system history.
Most of the 2,196 Apollo samples were examined decades ago, but a few were set aside for the future; recognizing that our instruments and analysis techniques would improve over time, NASA developed the Apollo Next Generation Sample Analyses (ANGSA) program to connect the Apollo generation of researchers to future generations. Gross and collaborators analyzed one of these samples, 73001/2, which was collected in an interesting region at the intersection of a light-colored mantle deposit and a fault scarp (a region where part of the surface is offset vertically from surrounding areas).
Location of the 73001/2 sample collection site (labeled “3”) with respect to the lunar module (LM). [Slide by Juliane Gross]
Gross’s team extracted a precious sample of lunar gas from the outer sample tube before discovering that the inner sample tube hadn’t been closed properly; during the sample collection, the astronauts had overfilled the tube, preventing the locking mechanism from closing completely. Using modern X-ray capabilities and a little creative problem solving, Gross and collaborators were able to collect the sample without contaminating it, paving the way to assessing its properties and cataloging its contents to be shared with other scientists.
With the planned Artemis lunar missions approaching, Gross notes that there is much to relearn that may have been forgotten in the half century since the Apollo missions — and since Artemis will touch down in an entirely different region from Apollo, there will be plenty of new things to learn as well.
Relationship between CO/CO2 ratio and distance from the Sun for various comets. [From slide by Olga Harrington Pinto]
The first of two DPS press conferences (recording available here) brought us updates on comet and asteroid research. The first speaker, University of Central Florida graduate student Olga Harrington Pinto, described a project to determine the rates at which comets produce gases like carbon monoxide (CO), carbon dioxide (CO2), and water (H2O). Pinto found that beyond 3.5 au, where heating from the Sun is minimal, comets produce more CO than CO2, while eight out of nine Jupiter family comets orbiting within 3.5 au are CO2 dominated. Intriguingly, Oort cloud comets orbiting within 3.5 au show a variety of behaviors, with the CO/CO2 ratio increasing with dynamical age. This goes against expectations, and it may indicate that galactic cosmic rays process the outer layers of these comets as they make their first foray into the inner solar system. Finally, Pinto reports that the median C/O ratio is 13%, which is consistent with comets forming within the CO snow line.
Demonstration of the irregular shape of the Lucy mission target Leucus as determined through stellar occultations. [From slide by Marc Buie]
Next, Marc Buie (Southwest Research Institute) introduced a worldwide citizen science effort to observe the five targets of NASA’s Lucy mission as they pass in front of background stars. These stellar occultations provide a way for researchers to determine the size and shape of distant asteroids, as well as whether they have any moons, rings, or dust. The occultation-observation project, which started in 2018, has taken Buie across the world and involved 500 observers. A major finding from the project is that all of the Lucy mission targets have significant topography (i.e., landforms and surface features), regardless of the size of the object. The project also discovered that one of the targets, Polymele, isn’t flying solo — it’s accompanied by a small moon nicknamed Shaun. Given Polymele’s shape and size, Buie speculated that the Polymele–Shaun system may be similar to the New Horizon’s target Arrokoth, except the two bodies never merged.
Finally, University of Arizona graduate student Adam Battle introduced the curious asteroid (52768) 1998 OR2, which has been designated potentially hazardous due to its size (2.2 km) and orbit. In order to constrain the asteroid’s rotation period and composition, Battle used data from a variety of sources, including visible spectroscopy, archival infrared spectroscopy, photometry, and observations from Arecibo and the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE). These data sources painted a conflicting picture of the asteroid’s nature, with evidence for the asteroid being either a carbonaceous chondrite — containing unaltered, primitive material — or an ordinary chondrite. Battle explored several causes for this discrepancy, landing on shock darkening and impact melting as the most likely causes. These processes, which don’t alter an asteroid’s composition but do affect its spectrum, can lead to a misunderstanding of the asteroid’s properties. This discovery adds to the surprisingly small sample of asteroids with known evidence of shock darkening. Press release
Juan Lora (Yale University), who was awarded this year’s Harold C. Urey Prize, described how our understanding of Titan’s surface and atmosphere has evolved. Titan, the largest moon of Saturn, has a massive, extended atmosphere mainly composed of nitrogen, which drives an active methanological cycle similar to the water cycle on Earth. And while some of Titan’s features are similar to Earth — it’s tilted by 26.7 degrees on its axis, giving it Earth-like seasons, and it’s the only other solar system body that hosts standing surface liquid — others are decidedly alien: its year lasts 29.5 Earth years, its day lasts 16 Earth days, and its abundant clouds are mostly methane (but a few are made of deadly hydrogen cyanide!). These similarities and differences make Titan an excellent candidate for comparative planetology: the study of how physical and chemical processes affect different worlds.
Lora notes that our knowledge of Titan has come a long way, both in terms of what we’re able to observe as well as what we’re able to model. Early models were able to approximate the current distribution of surface liquid, but these models required certain characteristics to be imposed to begin with to achieve that outcome. Today, self-similar models reproduce the north polar methane seas without these restrictions. Models also give us a way to explore Titan’s past climate, or paleoclimate; while the north pole is dotted with seas, the south pole contains dry seabeds, indicating that the southern hemisphere likely hosted seas in the past. While researchers have suggested that Saturn’s eccentric orbit drives Milankovitch cycles on Titan, resulting in a net northward movement of methane, there are still plenty of questions to be answered.
Luckily, the next decade will bring us a means of answering them: the Dragonfly mission. Among the mission’s many objectives is to understand how the surface and atmosphere interact, which will help scientists understand Titan’s past and present climate. Looking ahead, the Titan Orbiter recently endorsed by the Planetary Decadal Survey would provide long-term monitoring of Titan’s atmosphere.
Current Constraints on Ancient Venus (Martha Gilmore)
Martha Gilmore (Wesleyan University) was awarded this year’s Claudia J. Alexander Prize. Gilmore delved into the uncertain history of our neighboring planet, Venus. Today, Venus’s surface is a scorching 450°C, its atmosphere presses down with a crushing force more than 90 times stronger than Earth’s atmosphere, and all but 4% of its air is carbon dioxide. That’s Venus as we know it — but could it have been a more hospitable place billions of years ago?
Perspective view of Venus’s Fortuna Tessera constructed from NASA Magellan data. The color scale shows the emissivity of the region. [NASA/JPL/USGS]
The answer might lie in Venus’s unusual tesserae: rough, deformed, high-altitude regions of Venus’s surface. The average age of Venus’s 900 craters is somewhere between 300 million and 1 billion years (Gilmore uses 500 million years as a rough estimate), indicating that the plains regions were resurfaced around that time ago, and the tesserae are likely older. But just how old the tesserae are is up for debate — they could be 500 million +1 years old or 4 billion years old. Gilmore notes that the tesserae witnessed the creation of the plains, which means they were subjected to the chemical and thermal conditions that existed on Venus during that period of extensive volcanism.
More information about the tesserae came from the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) aboard the Venus Express orbiter. VIRTIS observations at a wavelength of 1 micron — a wavelength sensitive to changes in iron content in minerals — supported the idea that the tesserae contain felsic igneous rocks, which require water and plate recycling to form. This contrasts with present-day Venus, which is devoid of both water and plate tectonics. Given that Venus’s tesserae potentially overlapped with the presence of water, Gilmore encouraged the audience to consider how rocks on Venus would react not just to present-day runaway greenhouse conditions, but how they would react to water and then the greenhouse.
Future missions and laboratory work will further our understanding of Venus’s history (a Venus sample return mission isn’t impossible!), and, as Gilmore notes, finding a Venusian meteorite would go a long way!
This year’s Kuiper Prize goes to Bonnie Buratti (NASA’s Jet Propulsion Laboratory), who introduced the many instances of photometry being ahead of its time, hinting at discoveries that didn’t follow until much later. Buratti began by describing how researchers can use photometry to assess the roughness of surfaces in the solar system, noting that this technique gives us access to particles far below the resolution limit of our cameras.
There are many examples of photometry giving us the first hint at a significant discovery (too many to detail in this short summary!). Using photometric tools, researchers correctly predicted the presence of carbon dioxide on Saturn’s moon Iapetus, the methane-soaked surface of Saturn’s moon Titan, the plumes of icy Enceladus, and a population of retrograde moons around Uranus.
While photometry has been a major player in many discoveries, it may yet play a role in several unsolved mysteries as well. One example is the surface of Jupiter’s moon Europa. Europa exhibits limb darkening (it’s brighter at the center of its disk than at the edges), but it should be the same brightness across the disk, and it’s very forward scattering (i.e., photons striking particles on its surface are scattered roughly in the direction of the incident light rather than being reflected back). Buratti speculated on what the upcoming Europa Clipper mission might discover to explain these observations. Could icy slurries seeping up from below be compacting the moon’s surface? Or could particles from plumes be filling in cracks in the surface? Time will tell exactly how the mystery posed by these photometric observations is solved!
Hello from the 54th annual meeting of the AAS Division for Planetary Sciences (DPS), happening in London, Ontario, and virtually anywhere! This week, we’ll be bringing you updates on selected sessions from the meeting and other great planetary science coverage. Meeting updates will be posted Wednesday and Friday of this week, and the regular AAS Nova posting schedule will resume on Monday, October 10.
In the meantime, if you’re attending DPS, here are some events that might interest you:
Planetary Allyship Meeting Monday (10/3), 7:00 – 8:00 pm ET, Salon EF
Women in Planetary Science Discussion Hour
Tuesday (10/4), 12:00 – 1:00 pm ET, Salon HJ
Planetary Scientists of Color Networking Event
Tuesday (10/4), 5:30 – 6:30 pm ET, Salon DD1
Press Conferences
Tuesday (10/4) and Thursday (10/6), 12:15 – 1:15 pm ET, Zoom webinar
Reception for the Planetary Science Journal (cupcakes for all!)
Tuesday (10/4), 4:00 – 5:00 pm ET, Exhibit Hall Booth 112
JWST Townhall
Wednesday (10/5), 12:00 – 1:00 pm ET, Salon EF
DPS/Federal Relations Subcommittee Space Policy Town Hall
Thursday (10/6), 12:00 – 1:00 pm ET, Salon BB1
If you’re attending DPS in person, be sure to pop by the AAS Publishing booth (112) to speak to our publishing representatives and to pick up some journal swag. We hope to see you there!
Ben Cassese (Columbia University) has been selected as the 2022–2023 AAS Media Fellow.
In 2017 we announced a new AAS-sponsored program for graduate students: the AAS Media Fellowship. This quarter-time opportunity is intended for current graduate students in the astronomical sciences who wish to cultivate their science-communication skills.
We are pleased to announce that Ben Cassese, an astronomy graduate student at Columbia University, has been selected as our AAS Media Fellow for 2022–2023.
Before beginning his graduate studies, Ben majored in planetary science and history at the California Institute of Technology. Now a second-year graduate student in the astronomy department at Columbia, Ben works with David Kipping to search for moons orbiting planets outside our solar system and understand how the properties of exoplanetary systems can be inferred from subtle clues in transit light curves.
In addition to research, Ben writes for the graduate-student collaboration Astrobites, acts as a research mentor, and has explored his interest in science policy as a Lloyd V. Berkner Space Policy Intern. Between college and graduate school, he also successfully thru-hiked the 2,190-mile Appalachian Trail.
An image of Ben and collaborators during an observing run at Palomar. [Ben Cassese]
As the AAS Media Fellow, Ben will regularly write and publish summaries of the latest astronomy research on AAS Nova, assist in managing the distribution of press releases as part of the the AAS Press Office, and gain a broad understanding of the worlds of scientific publishing, communications, and policy. Ben will also be assisting with the press conferences at the upcoming 241st meeting of the AAS, so please say hello if you’re attending the meeting in Seattle, Washington, next January!
Jocelyn Belle is engaged in important duck-matter research. [Haley Wahl]
As we welcome Ben to the team, we’ll also soon bid farewell to Haley Wahl, our 2021–2022 AAS Media Fellow. Haley completed her graduate research on pulsars and defended her dissertation in August 2022. She currently lives in the Washington, DC, area with her new puppy, Jocelyn Belle, and works remotely as a science writer and content creator for the Massachusetts Institute of Technology Lincoln Laboratory.
Please join us welcoming Ben as our new Media Fellow and wishing Haley the best in all her future endeavors!
