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dwarf galaxy Leo P

Editor’s Note: This week we’re at the 245th AAS meeting in National Harbor, MD, 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.bsky.social on Bluesky for more coverage. The usual posting schedule for AAS Nova will resume on January 21st.

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Plenary Lecture: The Star Formation Engine, Stella Offner (University of Texas, Austin) (by Jessie Thwaites)

“The story of a star’s life is written at birth,” says Dr. Offner, whose plenary lecture describes the details of numerical simulations to understand the birth and evolution of stars in our Universe. She and her team in the STARFORGE project have created some beautiful animations of their simulation output, which made for riveting visuals in her talk (they also publish them on their website, so check their movies out here!).

She begins with the stellar initial mass function (IMF), which is known from observations but that they want to describe with their simulation from first principles. It’s a difficult problem to solve — there are multiple scales and many processes at play, and although we have incredible observations from JWST for star forming regions like the Carina Nebula, which is actively forming thousands of stars, this is only a single snapshot in time.

The star formation engine is a process with many scales, starting from a molecular cloud in a galaxy, which has a dense core region with an accretion disk. A forming star may have a protostellar outflow or a wind bubble, depending on its size, and when it eventually goes supernova it launches material back into the galaxy, beginning the process over again. Dr. Offner’s simulations need to cover 10 orders of magnitude in space and 20 orders of magnitude in density (that means that if the smallest region is of order 1 in both space and density, making simulations that consistently model regions that are 10,000,000,000 larger and 100,000,000,000,000,000,000 times more dense, and everything in between) — a huge feat! To do this, they use Frontera supercomputers and hydrodynamic codes to attack this challenge.

Their codes include a variety of processes, from physics models for self-gravity (which tell them how the gas interacts with itself), magnetic fields, and turbulence, to stellar feedback mechanisms such as protostellar outflows, stellar winds, radiation, and supernovae. They combine these with important microphysics considerations, including heating and cooling mechanisms and cosmic rays.

In one animation, they begin with a cloud of gas 10 parsecs across and initial turbulence conditions. As the simulation evolves, complex structures begin to emerge, and the first protostars form. The protostars begin to have outflows reaching hundreds of kilometers per second, and as more stars form, they begin to form and interact with each other in clusters. The first high-mass stars begin to interact, and eventually slow down due to feedback and supernovae from these massive stars, until the center of the cloud can be revealed in optical light. Through this process they are able to reproduce the IMF conditions, and even with 15 more simulations they find a very similar IMF, reproducing the observed IMF.

One of the elements that is new in these simulations but is incredibly important, Dr. Offner says, is cosmic ray ionization in the clouds. These charged particles are responsible for heating the dense gas and eventually the formation of molecules, which make them especially important to astrochemistry. They find the cosmic ray energy has an impact on the IMF, which leads them to ask if regions with high cosmic ray densities (like the centers of galaxies) might have a different IMF than other regions. To study star formation in galaxies in addition to their simulations, they team up with the FIRE (Feedback in Realistic Environments) simulation team to produce consistent simulations from the galaxy scale down to an accretion disk around a black hole. They find that the IMF does change in their simulations depending on the distance from the center of the galaxy — an important result for understanding how stars form in galaxies.

There is still more work to be done, Dr. Offner says. The simulations can include still more physics models and astrochemistry, important for understanding how chemical compounds and planets form, which is important to studying habitability over time. Trying to follow all of these chemical considerations is too expensive with traditional simulations, but are excellent problems to approach with machine learning. She and her team at the newly established NSF AI Institute for Cosmic Origins are working to understand these problems using robust machine learning techniques.

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Splinter Session: The Habitable Worlds Observatory: Current Status and Opportunities for Engagement (by Lindsey Gordon)

This splinter session discussed NASA’s next flagship mission after Roman launches, the Habitable Worlds Observatory (HWO). This was the main mission recommended by the 2020 decadal survey, and will be a sort of “SuperHubble,” with similar wavelength coverage but a 6–8 meter aperture (Hubble’s aperture is 2.4 meters across). This will be the first instrument capable of directly imaging an Earth-like planet, but any object in the infrared through the ultraviolet can be observed. The mission will have a coronagraph, a high-resolution imager, an ultraviolet multi-object spectrograph, and a not-yet-determined fourth instrument that will be decided on by community demand.

Dr. Makenzie Lystrup, the director of Goddard Space Flight Center, opened the session by thanking everyone who is engaging with HWO. She emphasized the importance of community in the project, both in its development and its long-term usage, and Goddard’s commitment to executing the project on budget and on schedule to produce a mission that will be a major community resource.

We then heard from one of the leads of the Science Community Engagement team. They want to get both the scientific community and the public excited about this mission as it searches for life in the universe. There is an upcoming meeting, HWO25, and they hope to involve the community in the conversations there. The remainder of the session included presentations from the science working groups (Living Worlds, Solar Systems, Evolution of the Elements, and Galaxy Growth), industry partners, “pop” talks from Early Career Researchers, and a mini “Town Hall” with tables from different groups to start discussion.

You can find out more about HWO on their NASA website or by requesting to join their Slack.

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Splinter Session: A Conversation About the Gemini Observatory Strategic Plan for the 2030s (by Lindsey Gordon)

The Gemini Observatory ran a splinter session to discuss their 2023–2028 improvement plan and the future of the telescope. Scott Dahm, the interim director, discussed the new instruments. GHOST, IGRINS-2, GPI-2, SCORPIO, and GIRMOS are all going online in that timeframe at both the North and South observatories, and these instruments make up a set of new spectrographs and imagers that will improve Gemini’s capabilities. GNAO is the new adaptive optics system for the North observatory and is scheduled to go online in 2028. Gemini is also getting a new proposal writing and execution platform, the Gemini Program Platform, in coming years to streamline and centralize observing.

Gemini’s critical science areas include exoplanets, time domain (transient) astronomy, galaxy science, and star and planet formation. The observatory will play a key role in selecting exoplanet targets for JWST, performing rapid transient followup, and providing advanced adaptive optics for observations.

The science team & NOIRLAB are highly involved in public outreach and community based astronomy. They’re adding a cultural residency program this year, doing anti-light-pollution work to keep Chile’s skies dark, and just celebrated the 20th anniversary of their Journey Through the Universe program reaching thousands of students in Hawai’i. The team is also supporting the transition of the management of Maunakea’s observatories to the Maunakea Stewardship and Oversight Authority.

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Press Conference: Exoplanets: From Formation to Disintegration (by Lexi Gault) (Briefing video)

An ALMA Survey of Circumstellar Disks in Young Binaries
Taylor Kutra (Lowell Observatory)

Stars and their planets are born out of clouds of gas and dust that collapse over time, but frequently stars are not formed alone but rather in binary pairs or larger groups. In order to understand how planets form in binary star systems, it is important to study the environments where they are born — the circumstellar disks of their host stars. Dr. Kutra presented ALMA (the Atacama Large Millimeter/submillimeter Array) imaging of the circumstellar disks of binary star system DF Tau. Prior to ALMA imaging, Dr. Kutra thought that only the primary star in the system had a circumstellar disk and any remnant light was noise; however, with the ALMA images it became clear that both stars in the system are surrounded by a disk of gas and dust. These observations provide the basis for future investigations into binary star systems and their journey to forming planets. | Press release

A New NASA Mission to Characterize Exoplanets and Their Host Stars
Ben Hord (NASA Goddard Space Flight Center)

Dr. Hord shared updates and science goals from the new NASA Pandora SmallSat Mission that plans to observe and characterize exoplanet host stars and exoplanetary atmospheres. This is a space-based mission, employing a 0.44-meter telescope that can observe simultaneously at visible and near-infrared wavelengths. During its 1-year primary mission, Pandora will observe more than 20 known exoplanet systems, collecting data on the host stars’ light profiles as well as spectra to identify the composition of exoplanet atmospheres. These observations will allow astronomers to better understand exoplanet atmospheric conditions and will aid in the search for habitable planets. Pandora will be able to perform follow up observations on exoplanet candidates observed with JWST and will be a critical tool in the exploration of exoplanetary systems. | Press release

X-Rays in the Prime of Life: Irradiating Vulnerable Planets
Scott Wolk (Smithsonian Astrophysical Observatory)

When searching for habitable planets in the galaxy, astronomers often target low-mass main sequence stars (M stars) as they are the most common star type in the galaxy. Dr. Wolk presented observations of M star Wolf 359 that is very bright in the X-ray. This star is about 10% the mass of our Sun and its habitable zone is very close to the star. However, this star is pumping out tons of X-ray radiation that can evaporate an exoplanet’s atmosphere over the course of a couple million years. This is very detrimental to any potentially habitable planet, but Dr. Wolk explained the conditions required for a planet to still be habitable under these conditions. Earth, for example, has a very massive reservoir of liquid water in our oceans, which under these X-ray conditions, could replenish the atmosphere for an extra 600 million years. However, this is still not a very long time for life to develop or persist, and Wolf 359 has emitted multiple flares, which would expose the planet to even more damaging radiation. Is there any hope left? If a planet had a water reservoir equivalent to 11 times the amount of water in Earth’s oceans, it would continue to have an atmosphere, so while not all hope is lost, X-ray emission from M-type stars poses a significant threat to their planetary systems’ habitability. | Press release

Bright Star, Fading World: Dusty Debris of a Dying Planet
Marc Hon (Massachusetts Institute of Technology)

In exoplanet systems, if a planet orbits too closely to its host star, the star will heat the planet into an extremely hot ball of lava. A small enough planet, smaller than Earth, is not able to hang onto its atmosphere, and as it orbits its star, the material evaporated from the planet will form a comet-like tail of material trailing behind the planet. Dr. Hon announced the Transiting Exoplanet Survey Satellite discovery of one such disintegrating exoplanet BD+05 4868 Ab. Through their observations, they have found that the planet has a long trailing tail of material and a smaller leading tail. From their measurements, this planet is losing one Moon’s worth of mass every million years, which would destroy a small planet completely. This discovery opens up the realm of dying planets, and we can continue to learn about them with further observations. | Press release (PDF)

JWST Exposes Hot Rock Entrails from a Planet’s Demise
Nick Tusay (Penn State University)

In the theme of dying planets, JWST observations have revealed the disintegrating entrails of planet K2-22b. As Tusay explained, when planets are disintegrating, you can study the composition of their layers as they shed. Using the JWST data, they modeled the compounds in the dust cloud coming from the planet. These models show that the compounds are not consistent with iron-dominated material, suggesting that this planet has not yet been stripped down to its core, and the compounds are not consistent with rock vapor. Looking for other plausible materials, they find their data is most consistent with CO2 and NO, which are “ice” vapors. But how could this planet so close to its star have ice? Tusay suggests that this planet may have formed further out but was thrown inward by a binary star companion. Further observations of similar systems will aid in understanding dying planets and their origins. | Press release (PDF)

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Dannie Heineman Prize for Astrophysics Lecture: Past, Present, and Future Cosmic Microwave Background Surveys, John E. Carlstrom (University of Chicago) (by Bill Smith)

The cosmic microwave background (CMB) is one of the most important pieces of evidence for our modern understanding of the cosmos, and Dr. John Carlstrom has played a key role in the development of the interferometry techniques and telescopes that led to the precise measurements of the microwave sky we have today. He was awarded the Dannie Heineman Prize for Astrophysics, awarded jointly by the American Institute of Physics and the American Astronomical Society and funded by the Heineman Foundation, for his “pioneering work on microwave interferometry and his leading role in the development of the South Pole Telescope.”

He shared how his own interest in microwave astronomy was born out of studying the Sunyaev-Zeldovich (SZ) effect, in which microwaves from the CMB are distorted when passing through galaxy clusters en route to Earth. As Dr. Carlstrom said, the SZ effect leaves a “shadow” of sorts in the sky in the microwave spectrum in the vicinity of the most massive objects. Because this “shadow” measures thermal energy, it can be used as a proxy for the mass of the cluster. He recounts building the “SZ Array” with Marshall Joy to take low-brightness images over an extended period of time to successfully measure the SZ effect and use it to calculate cosmological parameters like Omega matter and the Hubble constant.

The next project he focused on was DASI, the Degree Angular Scale Interferometer at the South Pole. From DASI data, Dr. Carlstrom and his team were able to measure the matter power spectrum to a high enough precision to conclude for the first time that dark matter was needed in the very early universe and were able to measure the polarization of the CMB for the first time.

Following this, Dr. Carlstrom discussed the South Pole Telescope (SPT), and the many ways it is groundbreaking. He showed preliminary work of a galaxy cluster catalog developed with SPT data showing the relationship between redshift and cluster mass. He then highlighted multiple results from younger scientists in the collaboration observing transient phenomena, like stellar flares, blazars, and asteroids. Dr. Carlstrom continued by highlighting the importance of polarization and CMB lensing, and how measuring the E modes and B modes would allow insight into the gravitational waves generated by inflation, and thus insight into inflation itself. To measure the B modes, though, would require measuring fluctuations in the CMB on order of 10 nanoKelvin, which is still out of reach, but a new SPT camera being built could lead to a future measurement. He concluded with a quick look to the future, noting that the SPT has multiple datasets over multiple years at this point, and that a new telescope called CMB-S4 is also in the works.

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Seminar for Science Writers: Bringing the Night Sky to Life: NSF–DOE Vera C. Rubin Observatory Will Revolutionize the Way We Explore the Cosmos (by Kerry Hensley) (Briefing video)

Thursday afternoon brought a special session for science writers introducing the Vera C. Rubin Observatory. The observatory is currently under construction on Cerro Pachón, a mountain in the Coquimbo region of Chile north of Santiago. There, it is dry, high, and the nights are dark — critical factors for the exceptionally broad and deep science that the observatory will enable. Though the wait for this highly anticipated observatory has been long, the wait is almost over, with the first image to be released this summer and the full science survey to be underway by the end of 2025. The mission of the observatory is to bring the night sky to life, which it will accomplish by scanning the sky for 10 years and creating a time-lapse record of the universe — in other words, the greatest cosmic movie ever made. The observatory is also notable for being the first project of similar scale to incorporate education and public outreach from the project’s inception. “The universe is universal,” and the Rubin team aims for anyone who is interested to be able to get involved through formal education, public outreach, and citizen science.

First up in the seminar was Sandrine Thomas, who got the audience acquainted with the basics of the observatory and its namesake, Vera Rubin. Rubin was an astronomer who provided the first convincing evidence for dark matter and advocated for women in astronomy. Fittingly, the Vera Rubin Observatory is the first major US observatory named for a woman. And don’t forget the name! Though astronomers love acronyms, Thomas emphasized how critical it is not to reduce the observatory’s name to “VRO” (there’s a list of recommended name variations on the observatory’s media page).

Rubin Observatory’s mission is to capture the cosmos, and to do that, it needs a wide field of view, a speedy telescope, and the ability to see faint objects. The 3.5-degree field of view — equivalent to the area of 45 full Moons — and fast-moving 350-ton telescope enable the observatory to take repeated images of the entire southern night sky in 3–4 nights. The observatory boasts a 3,200 megapixel camera — the largest digital camera ever constructed — and six color filters from near-ultraviolet to near-infrared. Looking ahead, the camera installation will take place in March 2025, with first look expected June/July 2025 and the survey expected to start late 2025.

Leanne Guy introduced Rubin’s four key science areas: dark matter and dark energy, Milky Way structure and formation, a census of the solar system, and the changing sky. Designing a survey that can advance our understanding of all four of these areas is challenging, so the team worked collaboratively with the scientific community to set the survey cadence. The result is a survey that will generate 2 million exposures over 10 years, raking in 20 terabytes of data each night. The most frequently surveyed fields, the “deep drilling fields,” will be visited roughly 1,000 times in those 10 years.

The scientific yields are immense: for the Milky Way, the survey will produce a map 1,000 times larger than previous surveys. For our understanding of dark matter and dark energy, the wide field of view and faint object detection will provide an avenue to study these phenomena and explore alternate theories of cosmology. The solar system census will uncover four times more solar system objects than we currently know, changing the game for planetary defense, among other benefits. Finally, Rubin will detect 10 million changes in the night sky every night, uncovering rare events and enabling detailed follow-up observations. Speaking of follow up, Rubin can act as a follow-up facility in its own right, and Guy asserted that the observatory will be ideal for following up on gravitational wave detections.

Tackling the data discussion was Yusra AlSayyad, who demonstrated why an observatory like Rubin couldn’t be built until now: after all, only 20 years ago, we were still getting Netflix via DVDs! The same technology that has allowed streaming and social media to proliferate has also enabled this groundbreaking observatory, which will snap an image every 40 seconds, collecting 60 petabytes (that’s 60 quadrillion bytes) of data in 10 years. In just a single year, the survey will more than double the number of raw optical and infrared images in existence.

This massive dataset requires thoughtful data management and distribution strategies. Minutes after changes in the night sky are detected, alerts will be sent out to enable followup. But the number of alerts — potentially as large as 10 million per night — would be overwhelming, so Rubin will partner with community brokers who will filter these alerts and send out a whittled-down number. The facility will also produce annual data releases, culminating in a 500-petabyte final release. As this is far too large to download onto a laptop, data users will interact with the data through a cloud-based science platform.

Beth Willman from the LSST Discovery Alliance expanded upon the data distribution policies of the observatory. Rubin data will be immediately available to anyone in the US and Chile, as well as scientists from participating institutions. The data will become available to all two years after collection. Willman highlighted the global nature of the endeavor, with 28 countries contributing to the physical construction of the observatory or the creation of its software. “It’s not your mother’s science,” Willman said, emphasizing that the massive amount of data that will be produced represents both a challenge and an opportunity to create a new paradigm in how science is done. Part of that new paradigm will be infrastructure that facilitates the participation of professional and citizen scientists across the globe. And the impact is likely to extend beyond astronomy, as the data management and discovery methods can be applied to other big-data fields.

Finally, Stephanie Deppe closed the session by introducing resources to learn more, including the Rubin media kit, images and videos, an opportunity to visit the observatory site this spring, and opportunities to receive an email digest or press releases.

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Press Conference: Galactic Histories and Policy Futures (by Archana Aravindan) (Briefing video)

A Dwarf Galaxy’s Stellar Halo Built by Accretion
Catherine Fielder (University of Arizona)

This study by Dr. Fielder and team offers a rare glimpse into the evolution of a small dwarf galaxy, NGC 300, and its role in building stellar halos. While massive galaxies grow through mergers, forming extensive stellar halos, dwarf galaxies have fewer opportunities for such assimilation. Using deep imaging from the DELVE survey, resolved star maps reveal intricate structures around NGC 300, including a northern stream that extends over 100,000 light-years. The metallicity of these streams suggests they originated from a smaller galaxy that NGC 300 pulled apart, driving the formation of its stellar halo through accretion. This opens exciting opportunities for future exploration of how dwarf galaxies can form and evolve with Rubin and Euclid. | Press release

The Boundary of Galaxy Formation: Constraints from the Ancient Star Formation of the Isolated, Extremely Low-Mass Galaxy Leo P
Kristen McQuinn (Space Telescope Science Institute and Rutgers University)

Satellite galaxies typically follow a pattern of initial bursty star formation that is later followed by a period of star-formation quenching close to the epoch of reionization. However, Dr. McQuinn and collaborators find that one particular low-mass galaxy, Leo P, underwent a slightly different process. This isolated galaxy experienced three distinct phases of evolution: early star formation, a pause post-reionization, and a later reignition of star formation. Unlike satellite galaxies near massive systems, where environmental effects such as tidal stripping may entangle with reionization, Leo P’s isolation could provide crucial insights into the role of reionization in halting star formation. Similar patterns are also observed in other low-mass galaxies. Dr. McQuinn’s findings suggest that reionization may suppress star formation in galaxies larger than ultra-faint dwarfs, with varying effects based on environmental factors. If extended pauses in star formation are common, low-mass galaxies likely contributed minimally to reionization. | Press release

Resolving 90 Million Stars in the Southern Half of Andromeda
Zhuo Chen (University of Washington)

The Local Group of galaxies, particularly Messier 31 (the Andromeda Galaxy or M31), is an ideal laboratory for studying galaxy astrophysics. As the Milky Way’s closest large neighbor, M31 allows for detailed exploration, with the ability to resolve hundreds of millions of stars. The Panchromatic Hubble Andromeda Southern Treasury (PHAST) survey, of which Dr. Chen is a part, has produced the largest and sharpest photomosaic of the southern disk of M31, spanning decades and composed of 600 overlapping Hubble snapshots. The central region hosts older stars, while the southern disk features prominent dust lanes and young star-forming regions like NGC 206, along with numerous young star clusters. Observations also include Messier 32, a satellite galaxy dominated by older stars. Detailed analysis reveals that M31’s star formation history spans four age groups: very young (3–200 Myr), young (30–500 Myr), intermediate (0.8–2 Gyr), and old (> 2 Gyr). Tracking the older stars reveals a typical disk galaxy lacking visible spiral structures. Conversely, younger populations highlight more defined spiral arm structures, with the youngest stars creating the most pronounced features. | Press release

Recent Space Policy Statements Regarding Our Dark and Quiet Skies
John Barentine (Dark Sky Consulting)

The COMPASSE (Committee for the Protection of Astronomy and the Space Environment) empowers the astronomy community to advocate for preserving dark and radio-quiet skies, which face growing threats from satellite constellations, solar power infrastructure in space, and commercial space advertising.

To address these challenges, the AAS has issued key statements:

  • Transparency in Spaceflight Activities: Space activities, including cislunar (space around the Moon) and interplanetary missions, should be conducted openly, with publicly reported trajectories.
  • Atmospheric Impacts: Satellite launches and reentries contribute to atmospheric pollution. Congress needs to fund research to study and minimize their environmental effects and ensure that companies that launch satellites take them into consideration.
  • Space Advertising: Obtrusive space advertising poses a significant threat to ground-based astronomy and should be prohibited. The US and AAS are leading efforts to prevent its proliferation.

COMPASSE has also endorsed the IAU resolution on protecting dark skies and engaged with the US State Departments to promote these goals. Through these actions, COMPASSE aims to safeguard the observational capabilities essential for advancing astronomical research.

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RAS Gold Medal Lecture: From the Cradle: Applying Basic Physics to Astrophysical Fundamental Questions, Gilles Chabrier (ENS-Lyon) (by Bill Smith)

In the spirit of collaboration between the United States and United Kingdom, it has become tradition for the winner of the Royal Astronomical Society (RAS) Gold Medal to present a lecture at a meeting of the American Astronomical Society, and the winner of the AAS’s Henry Norris Russell Lectureship to present at a meeting of the RAS. This year’s Gold Medal winner, Dr. Gilles Chabrier, presented on how ideas from statistical mechanics can inform our understanding of star formation and cosmology.

His goal for the first half of the lecture was to explain his theory for the stellar initial mass function, which is a probability density function that describes the initial masses of a stellar population. He began by reviewing random field theory and how it is based on two random fields, a velocity field and a density field, occupying a space. One can think of the giant gas clouds out of which stars form as a turbulent gas. That turbulent gas, however, also self-attracts under the force of gravity. Dr. Chabrier went on to show how these dual influences, turbulence and gravity, will result in overdensities collapsing into masses following a log-normal probability density function with two power-law tails.

After that, Dr. Chabrier focused on irreversible processes in cosmology. He explained how in our standard understanding of the universe’s expansion, the inhomogeneities in the universe are negligible in redshift, but that the question of homogeneity is coordinate dependent. He suggests the introduction of a local expansion rate to fulfill the need for a covariant calculation of the cosmological redshift. He then explains that large-scale structure can also be thought of as a result of this turbulence generating a random field in which overdensities develop due to the influence of gravity. For dark matter, which is collisionless, large-scale structure forms when dark matter particles begin crossing trajectories (called shell-crossing). This leads to turbulent flows with overdensities that collapse into what we know as dark matter halos. As Dr. Chabrier points out, though, this is an irreversible process, which produces entropy. This entropy production plays a crucial role in the expansion of the universe, and Dr. Chabrier concluded by arguing that the cosmological constant appears as a proxy to account for the entropy production of the expansion rate.

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Lancelot M. Berkeley − New York Community Trust Prize for Meritorious Work in Astronomy Lecture: Erik Tollerud (Space Telescope Science Institute), Clara Brasseur (University of St Andrews), and Kelle Cruz (CUNY Hunter College and American Museum of Natural History) (by Bill Smith)

Writing the line of code “import astropy” has become a rite of passage for nearly every astronomy researcher, and many people in the astronomy community have long noted the unrecognized and undervalued work that has gone into creating and maintaining software. This year, the AAS recognized this work by awarding the Lancelot M. Berkeley − New York Community Trust Prize for Meritorious Work in Astronomy to the entire Astropy collaboration “for their work developing and maintaining this code base, which provides underlying support for much of astronomy research as it is conducted today.”

Accepting the award on behalf of the entire collaboration were Dr. Erik Tollerud of the Space Telescope Science Institute, Clara Brasseur, a graduate student at University of St. Andrews, and Dr. Kelle Cruz of Hunter College. They began by playing an extensive list of all of the people who contributed to astropy on the big screen and thanking them for their contributions, then divided the talk into three parts that described the past, present, and future of Astropy.

Dr. Tollerud began by recounting Astropy’s origin story to a time in 2011 when he had to transform astrophysical coordinates and found himself struggling to navigate the many packages available. When reaching out to a mailing list about his idea for a more standard package, he was met with skepticism that it would be yet another package to navigate. He then explained how an initial group decided that this package would be developed differently. First, it would utilize Github (which was new at the time) for better collaboration, and adopt a “do-ocracy” philosophy, which Dr. Tollerud explains as “the work that gets done is the work someone will do.” He also credits the organizational structure of the early developers, saying “if you make the right structure, even cats can be herded.”

Dr. Cruz then described the current successes and challenges of the Astropy collaboration. She cites the original Astropy paper as being on track to be one of the most-cited astronomy papers ever as a resounding success. She also cites the thorough testing and stability of the core package as another success. She goes on to explain that the success of Astropy has presented new challenges. First, because Astropy is now such a critical piece of infrastructure for much of the astronomical community, including for most missions, testing and stability of the code are more critical than ever, requiring more resources and making it more challenging for people newer to software engineering to contribute. She then explained Astropy’s package structure, which includes core packages, coordinated packages, and affiliated packages.

Dr. Cruz also explained the governance structure of the collaboration, which included adopting a charter and policies for transparency. She also shared details about the Astropy collaboration’s increasing success in securing funding for the project. She thanked the many institutional contributors and highlighted contributions from the Flatiron Institute and NASA.

Clara Brasseur concluded the plenary by discussing the future of Astropy. They discussed how the core codebase is in a “maintenance phase,” but that maintenance for a software package like Astropy is still a lot of work, including bug reports, documentation, tutorials, and more. They highlighted a huge area for growth, Astropy Learn: a new website that hosts tutorials, mainly in the form of Jupyter notebooks, on many of the astropy modules. Clara concluded with a call to the audience to get involved and noting the possibilities that contributing can bring, saying “I’m a graduate student, and I’m up here giving a plenary talk! We have a place for any type of contribution.”

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super star cluster N79

Editor’s Note: This week we’re at the 245th AAS meeting in National Harbor, MD, 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.bsky.social on Bluesky for more coverage. The usual posting schedule for AAS Nova will resume on January 21st.

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HEAD Bruno Rossi Prize Lecture: Martin Weisskopf (NASA Marshall Space Flight Center) and Paolo Soffitta (INAF-IAPS) (by Jessie Thwaites)

Dr. Weisskopf says he expected to be surprised with the results from the Imaging X-ray Polarimetry Explorer (IXPE), but both he and Dr. Soffitta knew how important studying the polarization of high-energy objects in our universe would be to advancing X-ray astronomy. They, along with the entire IXPE team, are the recipients of this year’s High Energy Astrophysics Division (HEAD) Bruno Rossi Prize in recognition of the amazing science their instrument enables. (For a review of polarimetry, check out this Astrobites Guide!)

Dr. Weisskopf began the session by giving a brief history of how IXPE came to be. He realized that without considering polarization, the X-ray astronomy community would be missing a key element in their toolbox. They began by including a polarimeter on a rocket to look at Scorpius X-1, known to be a very bright X-ray source. With only 5 minutes to observe, they were able to prove the merit of their instrument on this short flight, which paved the way for new developments in the decades to come.

Next, they launched two types of polarimeter on the orbiting solar observer (OSO-8), and detected the Crab Nebula’s strong polarization, which is consistent with emission from relativistic electrons being bent by a magnetic field (synchrotron radiation). After this success, the team improved the instrument, and together the team proposed the mission to NASA. Although they weren’t initially selected, the mission that was selected ended up being cancelled due to budget issues, so the team re-submitted — and were selected! With one condition: that no data would be proprietary.

After launching the instrument in 2021, the surprises commenced; sources that were expected to have high polarization (from lots of synchrotron radiation) actually were weakly polarized, and vice versa. They observed a wide variety of sources, from magnetars and pulsars to supernova remnants and compact objects, and many more. They observed the bright magnetar 4U 0142+61, which has an energy dependence to its polarization, where both the polarization degree and angle change as a function of energy.

Dr. Soffitta begins his part of the lecture discussing the innovative techniques employed in the IXPE detector. They realized that they could harness the power of the photoelectric effect, where the electron would be emitted preferentially in the direction of polarization. This allowed them to build a broadband detector with sensitivity to many different source classes. Altogether, he says, they submitted the proposal for IXPE 13 times before it was finally selected to be built.

The results they find with this instrument are transformative to understanding these different source classes. They found that around 50% of the sources they studied had a polarization greater than 0, providing new insight into the magnetic field behavior in multiple source classes, and with important implications for particle acceleration happening in that source.

Dr. Soffitta describes a few of the important results so far with IXPE, starting with the polarization of active galactic nuclei. In NGC 4151, which is a Seyfert 1 galaxy, they find a polarization angle parallel to the radio jet, indicating that the corona is in the plane of the disk. On the other hand, in the Circinus Galaxy, which is a Seyfert 2 (meaning that we can’t see the central black hole but instead only see the surrounding torus), they find the polarization is instead perpendicular to the inner jet, which they interpret as the radiation being reflected. They find blazars to have 3–5 times higher polarization in X-rays than in lower wavelengths, which indicates the presence of electrons accelerated in the source emitting synchrotron radiation.

IXPE has enabled many possibilities for X-ray astronomy, including its fascinating results describing the mechanisms at play in many different source classes. Dr. Weisskopf leaves the audience with the directive to “enjoy wrestling with the scientific implications” of these astonishing results from IXPE.

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Press Conference: Discovering the Universe Beyond Our Galaxy (by Lexi Gault) (Briefing video)

Introduction: 100 Years Since Hubble Discovered the Universe Beyond Our Galaxy (Press Release)
Jeff Rich (Carnegie Science Observatories)

Though we have marveled at faraway galaxies for quite some time now, just 100 years ago at an AAS meeting in Washington, DC, Edwin Hubble announced his discovery of galaxies beyond the Milky Way. Setting the stage for today’s press conference, Dr. Rich explained that Hubble had detected a Cepheid variable — a star whose brightness changes cyclically over time — in the Andromeda Galaxy. With this detection, Hubble could determine the distance to Andromeda, and for the first time, discovered a celestial object beyond our own galaxy. This discovery, as Dr. Rich reminded us, was made possible by the work of many astronomers, including Henrietta Swan Leavitt’s discovery of the period-luminosity relationship for Cepheid variables, and Harlow Shapley, who measured the size of the Milky Way that made Hubble’s distance calculation possible. With access to great telescopes and technology, astronomers have been able to make leaps and bounds in our understanding of the universe in a very short amount of time. Next generation instruments will continue to allow scientists in this generation and the next to flourish and discover more and more about the universe in which we live.

The Hubble Tension in Our Own Backyard
Daniel Scolnic (Duke University)

One of the most pressing issues in cosmology is the Hubble Tension, which is the discrepancy between the prediction of the current expansion rate of the universe based on the current standard cosmological model and what astronomers observe locally. In order to attempt to reconcile this tension, the Dark Energy Survey Instrument (DESI), as Dr. Scolnic explained, has built its own cosmological distance ladder to attempt to make a very precise measurement of the Hubble constant. Through observing supernovae in the Coma Cluster, DESI has been able to very precisely measure the distance to the Coma Cluster. However, the standard model predicts a distance farther away from us than has been measured by DESI and by many investigations prior. Objects in the universe are closer than our current cosmological standard model predicts, which, as Dr. Scolnic emphasized, has pulled the Hubble Tension taught, creating a crisis.

JWST Reveals the Early Universe in Our Backyard
Nolan Habel (NASA Jet Propulsion Laboratory)

Dr. Habel takes us to cosmic noon, the peak of star formation in the universe, which occurred when the universe was just 2.5 billion years old. At this time, a significantly smaller fraction of the universe’s gas had been processed into stars, meaning this star formation occurred with many fewer metals than exist in the universe today. Metals are a driver of the cooling of the interstellar medium, allowing the gas to collapse and coalesce into stars and planetary systems. But observing star formation under these conditions is difficult. Dr. Habel and collaborators have used JWST observations to study the nearby star-forming region NGC 346 in the Small Magellanic Cloud that has similar metallicity to that of cosmic noon. They are able to take spectra of individual protostars — stars early in their formation — probing the formation processes that shine a light on how stars and planets may have formed at cosmic noon.

Growing in the Wind: Watching a Galaxy Seed Its Environment
David Rupke (Rhodes College)

Galaxies and their surroundings form an ecosystem in which gas travels into and out of galaxies, mixing materials, spreading metals, and enriching the circumgalactic medium. Dr. Rupke presented observations of Makani, the Hawai’ian word for wind, a galaxy actively seeding its environment with cool clouds of oxygen. The galaxy is surrounded by a nebula of gas extending 300,000 light-years that has been ejected by multiple hot winds that push material out of the galactic center. Simulations show that as these clouds travel outward, they cool, but this is difficult to observe directly as it occurs on very small scales. Using the Hubble Space Telescope, Dr. Rupke and collaborators imaged Makani in the far-ultraviolet, tracing the emission from oxygen that is five times ionized, which traces the gas where the cooling rate is at its peak. This imaging has set a benchmark for future observations of galaxies feeding their environments with future, stronger telescopes.

Three Quenched, Faint Dwarf Galaxies: New Probes of Reionization and Stellar Feedback (Press Release)
David Sand (University of Arizona)

Far from other galaxies, stranded out in the field, are three ultra-faint dwarf galaxies that have been discovered by Dr. Sand and his collaborators. Unlike the small faint satellites orbiting the Milky Way that are subject to life-altering interactions, these ultra-faint dwarfs are unperturbed, making them ideal targets for studying how the smallest structures in our universe form and evolve without complicated interactions with larger-scale structures. First discovered in images from the Dark Energy Camera Legacy Survey (DECaLS), the ultra-faint dwarfs were observed in more detail with the Gemini South telescope to really get a good picture of these fuzzy patches. From these observations, Dr. Sand reported, each of these galaxies has a single old, metal-poor stellar population, no recent star formation, and no gaseous components. This suggests that these galaxies either blew out their gas through supernova explosions or the reionization of the universe evaporated the gas from these galaxies. Further studies and discoveries of similar ultra-faint dwarf galaxies will provide more clues into the evolutionary conditions of these galaxies.

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Plenary Lecture: Are We Alone? The Search for Life on Habitable Worlds, Giada Arney (NASA Goddard Space Flight Center) (by Lexi Gault)

During this plenary lecture, Dr. Giada Arney presented the science goals and plans for the Habitable Worlds Observatory (HWO). This mission aims to answer one of life’s fundamental questions: are we alone in the universe? This observatory will be a space-based, large-aperture telescope with a diameter between 6 and 8 meters and will observe through ultraviolet, optical, and near-infrared wavelengths (100–2500 nanometers). As Dr. Arney described, HWO will be a “super-Hubble,” capable of detecting Earth-like planets and characterizing their atmospheres, searching for signs of life.

The search for habitable worlds, as Dr. Arney explained, begins with liquid water. Though there is no guarantee that all possible lifeforms in the universe require liquid water to arise, we begin the search with what we know about life, and life on Earth needs liquid water. This requirement limits the search for habitable planets to Sun-like and lower-mass stars that are cool enough to host potential habitable zones. Searching for Earth-like planets around these stars will reveal whether planets like ours are common or rare, furthering our understanding of how common life may be.

Once we identify candidate planets, the search for life requires the identification of biosignatures: molecules that could not be explained without the presence of life. Dr. Arney took us through a tour of a few biosignatures that will be searched for through atmospheric composition analysis. The first biosignature, ozone (O3), is the product of photosynthesis. Though ozone can be produced in small amounts through starlight splitting water vapor apart, the lasting presence of atmospheric ozone is only known to be produced by photosynthetic life over a long duration of time. Another biosignature, methane, is primarily produced by microorganisms and builds up more through biotic (i.e., biological) processes than abiotic (i.e., physical rather than biological) processes.

However, detection of these biosignatures is not 100% indicative of life 100% of the time. There are multiple instances in which we could recover a false positive biosignature. In the case of oxygen, Earth produces very little abiotic oxygen, but this is not true for other planets. For example, Venus has a small amount of ozone, likely produced by oxygen interacting with the planet’s surface materials. In the case of methane, it can form abiotically through chemical interactions between water and iron-rich minerals. This is the case for Saturn’s moon Titan, which has an atmosphere made up of long-lasting methane that replenishes very slowly over time. With the chance of false positive biosignatures, Dr. Arney emphasizes the importance of careful observations of full stellar systems to accurately identify potential habitable worlds.

To wrap up her talk, Dr. Arney highlighted the breadth of the HWO’s science. Though intended to search for life, HWO will be a very powerful facility that will seek to answer questions across a wide range of topics in astronomy including galaxy formation and evolution, evolution of elements over time, and detailed studies of our solar system. Even more, Dr. Arney urged, HWO will answer questions we have not yet thought to ask.

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Press Conference: New Findings About Stars Near and Far (by Archana Aravindan) (Briefing video)

A Predicted Great Dimming of T Tauri: Has It Begun? (More information)
Tracy Beck (Space Telescope Science Institute)

Dr. Beck studies “the” T Tauri, which is the prototype for an entire class of Sun-like stars in our galaxy. Originally thought to be a single star, T Tauri consists of two distinct systems: T Tauri North, commonly visible in optical wavelengths, and T Tauri South, a binary system obscured in the optical by a dusty circumbinary disk and located in the foreground of the northern system. In 2017 and again in 2021, T Tauri North experienced an unprecedented dimming of about 2 magnitudes — the first such event observed in over a century. Dr. Beck proposes that this dimming is caused by the T Tauri South binary system, which is moving along its wide circumbinary orbit toward T Tauri North. As it progresses, dust from the circumbinary disk is gradually obscuring the northern star along our line of sight. This process will eventually cause T Tauri North to disappear entirely from view.

A Super Star Cluster Is Born: JWST Reveals Dust and Ice in a Stellar Nursery (Press release)
Omnarayani Nayak (NASA Goddard Space Flight Center)

Recent observations from JWST by Dr. Nayak and team provide new insights into super star clusters, key sites of intense star formation 6–7 billion years ago. In the Large Magellanic Cloud, N79, a young super star cluster less than 100,000 years old, forms stars at twice the rate of the Milky Way, with JWST’s NIRCam instrument identifying more than 1,500 protostars and MIRI revealing younger stars forming centrally. Lower-mass stars form farther from the core, where five massive protostars, including one 40 times the Sun’s mass, dominate. Recently launched outflows (< 100,000 years ago) are detected by the Atacama Large Millimeter/submillimeter Array, while Chandra X-ray Observatory data confirm that the age of the super star cluster is close to 100,000 years. This super star cluster, forming stars 2–4 times more efficiently than 30 Doradus and twice as efficiently as the Milky Way, offers a vital glimpse into the earliest stages of protostar formation.

A Discovery of Ancient Relics in a Distant Galaxy
Kate Whitaker (Umass Amherst)

Globular clusters are ancient relics of the universe, formed between 13 and 11 billion years ago, often found in association with more massive galaxies. Early globular clusters were young and blue, becoming older and redder over time. Observations of galaxies 11 billion years ago provide a unique perspective on both old and young globular clusters, offering a glimpse into their evolution. Using the JWST-UNCOVER treasury program, Dr. Whitaker and team identified a galaxy with a smooth elliptical light profile (indicating a past merger), which they nickname the Relic. This galaxy hosts a mix of young, intermediate-mass, and old associated star clusters with many remaining undetected. The findings suggest old clusters formed in situ, intermediate ones arose from tidal interactions and accretion, and young clusters also likely formed from accretion events. These clusters reveal the formation history of the Relic galaxy, offering a unique laboratory to test and improve theories of globular cluster formation.

Exploring the Sun’s Active Regions in the Moments Before Flares
Emily Mason (Predictive Science Inc.)

Solar flares, which are powerful bursts of energy from the Sun, occur when magnetic energy in the Sun is converted into light and motion. They can cause significant damage to satellites and communication systems around the Earth and their timing remains difficult to predict. Using data from the Solar Dynamics Observatory across four channels (which will allow for a range in temperatures/wavelengths), Dr. Mason and team analyzed coronal loops above active regions in the Sun. Observations focused on the active regions at the solar limb, avoiding overlapping active regions and ensuring no major flares occurred in the six hours prior for clean detection. Comparing light variability over six hours revealed that loops above active regions were more active, with fluctuations peaking 1-2 hours before a flare, particularly in cooler plasma. Rapid, small-scale brightness spikes often preceded confined flares without coronal mass ejections (CMEs). This method shows promise for predicting flares and is now being tested on more complex and blind cases to determine the accuracy of the predictions as well as to investigate the drivers of these small-scale variabilities.

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Plenary Lecture: Revealing the Solar Neighborhood’s Diversity and the Milky Way’s Substellar Halo, Aaron Meisner (NSF NOIRLab) (by Lindsey Gordon)

Dr. Meisner works on a census of the local solar neighborhood, with a focus on brown dwarfs. Brown dwarfs fill in the mass range between red dwarfs, the smallest “real” stars, and large planets. They’re sometimes called “substellar objects,” and they most likely formed like stars do. These brown dwarfs are cold, old, and have low metallicities. They can be hard to study because there is a lot of degeneracy between their temperatures, masses, and ages, as they cool very slowly over billions of years. Their spectra have a lot of humps due to molecular absorption in their atmospheres, and they fall into the L, T, and Y spectral classes.

Why study brown dwarfs? There are lots of them and they’re near us. They can be used as an easier-to-study analog of exoplanetary atmospheres and to contextualize our Jovian planets. With long lifespans, they trace early galactic structure and the Milky Way’s initial mass function.

There are no known Jupiter-sized brown dwarfs, but we think they should exist. WISE 0855 is the coldest known brown dwarf (about 100K hotter than Jupiter) and is only 2 parsecs away from us, so we thought we would’ve found more of them. In the search for more of these cold stars, Dr. Meisner’s team instead found new classes of brown dwarfs in the thick disk and halo of our galaxy.

The primary data these studies used was from the WISE mission, which is an infrared wide-field survey satellite. With more than 60 million exposures to look through, using citizen science / participatory science was necessary to identify the brown dwarfs in the data. Brown dwarfs are identified by their color — red in WISE data — and their rapid motion. The team produced mini movies of the WISE observations that volunteers from around the world classified through the Backyard Worlds Zooniverse program. Since 2017, volunteers have performed 11.5 million classifications and found 4,200 candidate brown dwarfs. The team also launched the Backyard Worlds: Cool Neighbors program, which uses AI and human co-classification. A neural network preselects the most likely candidates to show to the volunteers, and this method has given them a 3x boost in classifications. The incorporation of AI doesn’t take away from the human element of a participatory science project. The team has a big emphasis on community building; the science team meetings are attended by volunteers to give feedback and contribute.

types of brown dwarfs

Three types of progressively cooler brown dwarfs and their characteristics (click to enlarge). Y dwarfs are the coldest of substars. [NASA/JPL-Caltech with annotations from the Backyard Worlds project]

Some exciting results coming out of this work include filling out the census of brown dwarfs of spectral type Y. This new population has changed our understanding of the ratio of main-sequence stars to brown dwarfs from 6 to 1 down to 4 to 1, a huge increase. They’ve also found many more cold metal-poor “ultra-cool dwarfs” (T < 2700K) in the halo and disk. With better position data these can be sorted into specific halo substructures to tell us about the history of galactic star formation. The project also found the very first extreme T-type subdwarfs, with temperatures below 1400K. This is the first glimpse into the Milky Way’s substellar halo, and it forced them to actually extend the classification scheme to encompass both the temperature and the metallicity of brown dwarfs. The first hypervelocity ultra-cool dwarf was also found, and at 450 km/s, it’s nearly at the local escape velocity.

Then there is “The Accident.” WISEA 1534-1043 is a very cold (~500K) Y-type brown dwarf that was found purely by accident during Backyard Worlds. It’s a 6–8 magnitude outlier from other known brown dwarfs and has been confirmed by WISE, Gemini, Hubble, Spitzer, and JWST to be a brown dwarf just 16 parsecs away. It has a crazy spectrum compared with other brown dwarfs, which is part of what led them to add metallicity into their classification scheme.

JWST spectra of brown-dwarf atmospheres see molecular atmospheric absorption lines including methane, ammonia, and water. Under review for publication are the first ever detection of phosphine in the atmosphere of Wolf 1130 C, a 620K brown dwarf, and the first ever detection of silane (SiH4) in the atmosphere of The Accident. We’ve been expecting these features and trying to find them in our own solar system, but this might be the first time we’ve actually seen them.

In the new era of Big Data and next-generation surveys, participatory science is going to become ever more important for astronomers. Extremely large telescope programs like Rubin, LSST, and Euclid should increase our count of brown dwarfs by a factor of 15 and help fill out the census of our neighbors.

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Newton Lacy Pierce Prize Lecture: The Evolution, Influence, and Ultimate Fate of Massive Stars, Maria Drout (University of Toronto) (by Lindsey Gordon)

Dr. Maria Drout was awarded the 2024 Newton Lacy Pierce Prize for “revealing discoveries of the evolution, influence, and end states of massive stars through the study of explosive transients and resolved stellar populations.”

Massive stars are objects that every field of astronomy, from planetary science to cosmology, could use a better understanding of. Multi-star systems are ubiquitous in astronomy, and massive stars almost always form with at least one companion, with two-thirds of those systems interacting with their companion. There are many possible evolutionary pathways for these binary systems, the steps along which Dr. Drout and her team investigate. With the advent of gravitational wave astronomy, mergers between the possible compact object (neutron star or black hole) remnants of these systems are now observable in multiple messengers.

Dr. Drout discussed a potential scenario where two massive stars in a binary evolve into a binary pair of neutron stars. Over the course of their lifetimes, one star may go off as a supernova, the outer layers of one star may be stripped away by the other, the two may evolve together in a common envelope, and finally the second star must go off in a unique type of supernova.

The first supernova in the system can be found through the rise of wide field time-domain monitoring surveys, which now give us some 20,000 events per year. Recent studies have shown the progenitors of these core-collapse supernovae have properties that we didn’t expect and may in fact be hydrogen-poor core-collapse supernovae. These have low ejecta masses and high rate, which suggest a contribution from a (comparatively) lower-mass binary companion. We expect a lot of these stars to exist, but need to understand just how many of them there are, their metallicities, and their explosion properties. They also need better constraints on the fate of the surviving companion star.

At some point in the system’s lifespan one or both stars becomes a stripped helium star (He stars). The outer hydrogen envelope is removed and the hot helium core is revealed. Theories of binary evolution suggest they should be common, and they’re the favored progenitor for hydrogen-poor core-collapse supernovae. Dr. Drout’s group found the first population of these stars by reprocessing Swift Ultraviolet/Optical Telescope photometry data and looking for hot, ultraviolet-bright sources. Follow-up spectra on some of these systems showed deep He II absorption lines, indicating very hot, low luminosity stars with a lot of helium. From here, they’re looking to form a more complete sample of these stars to do population statistics with. Within the sample they have additional data on, there is at least one system that has an orbital period indicative of a binary between a stripped helium star and a compact object, which could be on its way to becoming a neutron star binary.

The common stellar envelope stage of a system occurs when one star fills its Roche lobe and begins to unstably transfer mass to its companion. The two stars can then either merge or eject the outer envelope and form a tighter binary system. Numeric simulations of these systems are tough, and there are no systems where we have measurements of the system both before and after it entered a common envelope. We mostly think these systems are a white dwarf and a main-sequence star, but knowing for sure if the two evolved together or just got caught by gravity is tricky. Stellar clusters — where all the stars are about the same age — present a viable opportunity for finding systems that co-evolved. The team was able to find 55 candidates for white dwarf–main-sequence binaries in clusters for future study of this phase of evolution.

At some point, a second supernova has to go off in the system to end up with two compact objects for a neutron star binary. This second supernova is also hydrogen-poor and has been through a lot in its evolution. These “ultrastripped” supernovae have very low masses and eject only about one solar mass of material. They are fainter and evolve more rapidly than other core-collapse supernovae, which makes them difficult to observe. However, the new wide-field surveys are finding so many transient events that we now have a small population of candidates for this type of supernova.

These events are just possible landmarks along the way to the compact object binaries lighting up the gravitational wave sky. Dr. Drout’s work represents the exciting new stellar populations that are still very much in the discovery phase of our understanding.

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Cassiopeia A

Editor’s Note: This week we’re at the 245th AAS meeting in National Harbor, MD, 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.bsky.social on Bluesky for more coverage. The usual posting schedule for AAS Nova will resume on January 21st.

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Bronze Award for the University of Michigan from the Physics and Astronomy SEA Change Committee (by Jessie Thwaites)

At the beginning of the morning’s sessions, Dr. Dara Norman (AAS President) announced that the University of Michigan Department of Astronomy has earned a Bronze Award from the Physics and Astronomy SEA Change Committee (read the AAS press release here). The award recognizes the University of Michigan Astronomy Department’s work towards understanding obstacles to diversity, equity, and inclusion in their community, in order to engage all members of their community. They have developed a five-year plan to address any issues identified in their assessment. The University of Michigan Astronomy Department is the first astronomy department to receive this award.

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From the Smallest Things to the Greatest Results — The Incredible Power of the Chandra X-ray Observatory, Dave Pooley (Trinity University and Eureka Scientific, Inc.) (by Jessie Thwaites)

X-ray vision has long been considered a superpower — and the Chandra X-ray Observatory has that power! Dr. Pooley begins his talk by saying that summarizing the successes of X-ray astronomy, or even just those enabled by Chandra, is impossible in a mere 40 minutes. So, he set some of the Chandra greatest discovery images to one of his favorite great hits: Kermit the Frog’s Rainbow Connection. From intricate maps of our solar system, images of merging galaxies, and microlensed galaxies, to understanding of cosmic structures, Chandra has enabled incredible discovery over the past 25 years since launch.

But making these images, Dr. Pooley says, is more than detecting — it was designing and focusing an incredible instrument, and in particular, incredibly smooth mirrors. X-rays have to be focused at grazing incidence, otherwise they will pass right through the mirror, and any imperfection on the surface degrades our ability to focus the instrument. So at the time of  Chandra design and development, the team designed the smoothest mirrors ever produced. If the mirrors were the size of Earth, Dr. Pooley says, the largest imperfections would be a mountain only a meter tall! This incredible feat of engineering has enabled the incredibly precise images that drive the cutting edge science done with Chandra.

Dr. Pooley goes on to highlight some of the amazing science done with Chandra. With its exemplary resolution, Chandra is able to resolve 100 times more sources in the globular cluster 47 Tucanae than its predecessor, ROSAT, and where ROSAT could not detect any sources in Messier 4, Chandra can detect around 100 of them. These new images allow the team to study the dynamics of the cluster and how binaries are forming inside them.

Chandra has also unlocked our current understanding of how particles are accelerated in supernovae, by resolving their gas structure. In a supernova, a forward-moving shock is propelled by the explosion into the gas surrounding the star, and a reverse shock pushes particles back toward the supernova. Electrons accelerated by the forward shock produce synchrotron radiation that has been imaged by Chandra, providing key evidence to describe how cosmic particles are accelerated in supernovae. It was also the first observatory to detect X-rays from the merger of two neutron stars in the multimessenger discovery of GW170817, showcasing its power as a time domain and multimessenger astronomy instrument.

The science that can be done with Chandra is not just monumental, it’s transformative. Imaging galaxy clusters with Chandra has also furthered our understanding of dark matter. Through Chandra imaging of the Bullet Cluster, which is unique in that it is actually the product of two colliding galaxy clusters, scientists can find proof of the existence of dark matter. While normal matter is subject to drag forces, dark matter is not, so the normal matter that emits in X-rays observed by Chandra is concentrated towards the center, while most of the mass of the cluster is concentrated farther away, as shown in the figure below.

Bullet Cluster

Image of the Bullet cluster by Hubble and Magellan telescopes, with a map of the normal matter (seen by Chandra, pink) and dark matter (blue) shown on top. [X-ray: NASA/CXC/CfA/M.Markevitch, Optical and lensing map: NASA/STScI, Magellan/U.Arizona/D.Clowe, Lensing map: ESO WFI]

Dr. Pooley also highlights the dedication of Chandra scientists to making their science accessible to all. With excellent software and documentation for newcomers, they have worked to make their science accessible. In the future, spacecraft like AXIS and eventually Lynx will hopefully come online to extend the success of Chandra even further. When it was announced that Chandra might lose funding, the astronomy community came together in the movement to #SaveChandra (also covered in this Astrobite). Continued advocacy is needed to keep our high energy eye on the sky funded and operating. As Dr. Pooley says, Chandra is still working beautifully and making breakthrough scientific discoveries today. It’s essential to keep this magnificent spacecraft operating so that we can continue to make amazing discoveries.

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Press Conference: Black Holes & New Outcomes from the Sloan Digital Sky Survey (by Lexi Gault) (Briefing video)

A Variable X-Ray Monster at the Epoch of Reionization (Press Release)
Lea Marcotulli (Yale University)

At the center of most galaxies in the universe lies a supermassive black hole. When these black holes are gobbling up galactic material, they become some of the brightest objects in our universe. Dr. Marcotulli announced X-ray observations taken with Chandra and NuSTAR of one such object, J1429+5447, which lies in the epoch of reionization — just 900 million years after the Big Bang. J1429+5447 is the brightest active supermassive black hole observed in X-rays at this distance and is the farthest source ever detected by NuSTAR. These observations reveal extreme X-ray variability, which is indicative of powerful relativistic jets coming from J1429+5447. This discovery provides the opportunity to study the relationship between supermassive black hole growth and jet-powering mechanisms.

JWST’s Little Red Dots and the Rise of Obscured Active Galactic Nuclei in the Early Universe (Press Release)
Dale Kocevski (Colby College)

Recently discovered with JWST, little red dots are red compact objects with unusual colors that have evoked many questions from astronomers. If these objects are galaxies powered by stellar light, they introduce the “over-massive galaxy problem” — these galaxies would be much too massive much too soon after the Big Bang given current cosmological theories and galaxy formation models. A new study, led by Dr. Kocevski, compiled a sample of 341 little red dots to further investigate these perplexing objects. They find that these objects exist primarily between redshifts of z~4 to z~8 and are more numerous than the expected number of quasars and X-ray active galactic nuclei in this range. Spectroscopy of these little red dots reveals broad emission lines, a sign of a fast-moving accretion disk orbiting an active supermassive black hole. Though these galaxies are primarily powered by supermassive black holes — solving the over-massive galaxy problem — further studies of these sources will help to understand how their central black holes formed and how the galaxy catches up to its black hole.

Revealing the Mid-Infrared Properties of the Milky Way’s Supermassive Black Hole (Press Release)
Joseph Michail (Center for Astrophysics | Harvard & Smithsonian)

Using JWST, Dr. Michail and collaborators have detected the first-ever mid-infrared flare from our galaxy’s central supermassive black hole Sagittarius (Sgr) A*. Over the past 30+ years, researchers have observed flares in Sgr A* at other wavelengths, but until this study, have yet to observe a flare in the mid-infrared. This new detection fills the gap between near-infrared and radio observations of flares in Sgr A* and provides a new view in understanding the microphysics responsible for the formation of flares.

Black Hole Archaeology: Mapping the Growth History of Black Holes Across Cosmic Time (Press Release)
Logan Fries (University of Connecticut)

With the Sloan Digital Sky Survey (SDSS) Reverberation Mapping project making mass measurements of hundreds of black holes, Fries and collaborators have been able to use these masses in conjunction with spectroscopic observations to measure the spin of a sample of black holes. The spin of a black hole is important as it encodes the growth history of the black hole. If a black hole builds its mass through accreting material, the black hole will spin up rapidly, and if a black hole builds its mass through mergers, the black hole will spin down. Through this study, they find that many black holes spin up quickly, and that black holes in more distant galaxies tend to spin up more than those in the nearby universe. This challenges the expectation that most black holes gain mass through mergers, and future observations with JWST will help to further understand how black holes have grown over time.

The SDSS-V Local Volume Mapper: Early Data and Science (Press Release)
Dhanesh Krishnarao (Colorado College)

SDSS has employed a set of four robotic telescopes to map the Milky Way’s interstellar medium to further understand how star formation occurs. Dr. Krishnarao presented the first data and science from the SDSS-V Local Volume Mapper (LVM), a survey aimed at taking spectra covering various emission lines for a large section of the Milky Way. These observations will allow scientists to observe individual stars’ impacts on the surrounding gas, which are key to understanding how galaxies form stars and evolve. Another important aspect of SDSS-V is its Faculty and Student Team (FAST) program, which provides support for students and faculty from minority-serving institutions to join the collaboration. The first data from LVM will be publicly available in data release 19 from SDSS.

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Henry Norris Russell Lectureship: The Cosmic Triangle: Probing the Dark Side of the Universe, Neta A. Bahcall (Princeton University) (by Archana Aravindan)

For Dr. Neta Bahcall, the Henry Norris Russell Lectureship holds a special significance. Dr. Henry Russell played a significant role in establishing Princeton, where Dr. Bahcall has spent nearly 50 years, as a leading center for theoretical astronomy! Additionally, her husband Dr. John Bahcall was also awarded the lectureship in 1999, making them the first couple to win the award!

Dr. Neta Bahcall receives the Henry Norris Russell lectureship from Dr. Dara Norman, President, AAS.

Dr. Bahcall begins her talk by providing a brief history about how the concept of dark matter came about. In the 1970s, the accepted fraction of matter (Ωm) in the universe was believed to be 1, indicating that all the matter in the universe was accounted for. But several eminent astronomers, including Fritz Zwicky, did not think that was true. The concept of dark matter (or matter we cannot see) was already floating around, but few people believed in it. Dr. Bahcall and her collaborators set out to observationally determine the value of Ωm, helping us understand if there truly is mass that we cannot see! They did this in two ways:

  1. Cluster correlation function: This function indicates how clusters of galaxies are distributed in space. Dr. Bahcall found that this function was 20 times stronger than the galaxy correlation function (which indicates how galaxies are distributed in space!). This discrepancy indicates that we see a large-scale structure in the universe and implies that the distribution of all the mass is not just tracing the light. There must be some mass that is not accounted for and thus Ωm cannot be 1. Dr. Bahcall and her collaborators determined that the fraction of baryonic matter (matter that interacts with light) should instead be closer to 0.3, and there must be some other form of matter that is not tracing the light. This discovery swung open the door for several models of dark matter.
  2. Mass-to-light ratios: Additionally, Dr. Bahcall also made use of another method to confirm this new value of Ωm. She calculated the total mass present in a given region of space based on its observed luminosity, essentially providing an indication of how much matter exists relative to the amount of light we can detect. This ratio is called the mass-to-light ratio or M/L. Higher M/L ratios suggest that all the matter is just not contained in stars (which contribute to the luminosity) and a larger proportion of dark matter is present.

This led Dr. Bahcall to set up a figure known as the cosmic triangle, which is a way of representing the past, present, and future status of the universe. The most precise measurements of the three quantities confine the universe to a strip in the plot. The three strips overlap at the ΛCDM model, which is in best agreement with observations.

Dr. Bahcall also touches upon the recent state of the field and all the ongoing questions about where the dark matter is actually located. New results from the Sloan Digital Sky Survey indicate that the M/L ratio increases up to a certain limit and it flattens out as we eventually go to larger and larger scales. This shows that most of the mass in groups comes from dark matter in galaxy halos, and there is no need for any additional dark matter that fills the space between large clusters.

Throughout her lectureship, Dr. Bahcall stresses the beauty of doing science. “It’s about how we don’t understand where we are and go step by step to figure it out!” she says. She wraps up her talk by thanking her mentors, collaborators, and grad students, and by giving a moving tribute to her wonderful family and (late) husband.

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Press Conference: New Information from Milky Way Highlights (by Lexi Gault) (Briefing video)

Infrared Echoes of Cassiopeia A Reveal the Dynamic Interstellar Medium (Press Release)
Jacob Jencson (California Institute of Technology/IPAC)

Cassiopeia A light echoes

JWST’s near-infrared view of Cassiopeia A’s light echoes. Click to enlarge. [NASA, ESA, CSA, STScI, Jacob Jencson (Caltech/IPAC)]

Cassiopeia A is the youngest core-collapse supernova in the galaxy whose light has propagated through the Milky Way, creating infrared echoes that light up interstellar clouds of cold gas and dust. Dr. Jencson presented new JWST images that show the most detailed pictures of these echoes that have ever been taken. As the echoes propagate, the 3D geometry of the interstellar gas and dust is revealed based on how long it has taken the light from these echoes to reach Earth. These images reveal surprising sheet-like structures on solar system–sized scales, opening up new avenues to study the formation of structure in interstellar clouds.

A Path-Breaking Observation of the Cold Neutral Medium of the Milky Way Through Thermal Light Echoes (Press Release)
Joshua Peek (Space Telescope Science Institute)

The detailed JWST observations of the light echoes surrounding Cassiopeia A illuminate a prototypical piece of the interstellar medium, which has allowed Dr. Peek and collaborators to explore the properties of the cold neutral medium that makes up 40% of the gas in the Milky Way. From the images, the structure of the cold neutral medium appears to have bundles of longer filaments and knots, which are similar to structures seen in simulations of magnetized gas. Magnetized gas resists compression, but stars form out of cooling and compressing gas, so further studying these small structures in the cold neutral medium will aid in understanding how gas collapses to form stars.

three views of the Ring Nebula

Left: Hubble Space Telescope image of the Ring Nebula. Center: Radio emission from carbon monoxide molecules as seen by the Submillimeter Array. Right: Infrared image of JWST showing contours of the carbon monoxide molecules that are moving perpendicular to our line of sight. Click to enlarge. [NASA/ESA/O’Dell/Ferland/Henney/Peimbert/Thompson; SMA image and SMA/JWST image overlay: Joel Kastner/RIT]

Imaging an Astronomical Icon in 3D: A New View of the Ring Nebula (Press Release)
Joel Kastner (RIT Center for Imaging Science)

The Ring Nebula is an iconic astronomical object, and despite its frequent stage time, the intrinsic 3D structure of the ring has yet to be fully understood until now. Dr. Kastner presented Submillimeter Array imaging of the Ring Nebula from which a 3D model of the nebula was created. The gas in the nebula appears in a clumpy ellipsoidal shell with holes on both sides, roughly the shape of a barrel. These holes are likely driven by a binary companion that created strong, high velocity outflows through the center of the shell. From this model, they find that the gas was ejected from the central star around 6,000 years ago. Uncovering the 3D structure of planetary nebulae, like the Ring Nebula, allows scientists to better understand the ending stages of intermediate-mass stars.

X-Ray Echoes from Sgr A* Provide Insight on the 3D Structure of Molecular Clouds in the Galactic Center (Press Release)
Danya Alboslani (University of Connecticut)

Similar to infrared echoes from Cassiopeia A, X-ray echoes from the Milky Way’s central black hole Sagittarius A* reveal the 3D structure of molecular clouds near the galactic center. Alboslani presented two decades of X-ray echo observations from the Chandra X-ray Observatory and the resulting 3D maps of two molecular clouds, the Stone and Sticks clouds, in the Milky Way’s central molecular zone. These clouds exist in an extreme environment with temperatures and densities much higher than elsewhere in the galaxy. Through comparing the X-ray observations to submillimeter wavelength observations of the same clouds, the duration of the X-ray flare can be constrained based on the gaps in structure shown in the X-ray imaging. They find the flare to be no longer than ~5 months. These 3D maps provide further insight into the conditions that lead to star formation in the central region of the galaxy.

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Plenary Lecture: A Detector Backstory: How Silicon Detectors Came to Enable Space Missions, Shouleh Nikzad (Jet Propulsion Laboratory) (by Bill Smith)

Dr. Shouleh Nikzad began by expressing her belief that the development of any new technology goes through three phases: invention, innovation, and infusion. In her plenary talk, she discussed these three phases as they applied to the development of silicon detectors for the ultraviolet (UV) light spectrum. She began with an overview of why the UV part of the spectrum is critical for astronomy, noting the many electron transitions that can be seen in ultraviolet spectra and applications for understanding planetary atmospheres. However, detecting the UV spectrum presents unique challenges, notably that UV radiation is absorbed within a few nanometers of the surface it hits, which means the designers of UV detectors must have exquisite control over the surfaces they develop.

Dr. Nikzad then shared a few of the reasons why silicon specifically was used to develop UV detectors, including the widespread adoption of silicon technology in industry. This widespread adoption meant that the existing infrastructure for the technology already existed and that it could be scalable for the next generation of flagship telescopes.

To create these silicon detectors, Dr. Nikzad and her group use a technique called atomic layer deposition, which is a technique that can create a very thin film on a surface with a high degree of control over the thickness. By using this technique, they were able to develop silicon detectors that, for the first time, could count single photons in the UV spectrum. She then explained how they were able to develop a bandpass filter for these detectors that would enhance UV detection and reject visible light.

Dr. Nikzad concluded by providing a tour of missions and potential future missions using this technology, including the Zwicky Transient Facility, FIREBall-2 (The Faint Intergalactic Medium Redshifted Emission Balloon Telescope, SPARCS (the Star-Planet Activity Research CubeSat), and UVEX (the Ultraviolet Explorer).

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Annie Jump Cannon Prize Lecture: The Icy Origins of Planetary Systems, Jenny Bergner (University of California, Berkeley) (by Lindsey Gordon)

Dr. Jenny Bergner received the 2024 Annie Jump Cannon Award, which is “for outstanding research and promise for future research by a postdoctoral woman researcher.” The award citation is for “…her innovative astrochemical work at the intersection of laboratory experiments, theory, and observations, which has established new pathways to interstellar chemical complexity.”

Dr. Bergner’s work focuses on the chemistry of stars and planets during their formation. Baby stars are surrounded by protoplanetary disks, which are flattened disks of material that have a high enough density to clump together into planetesimals. Planetesimals are solids that are too small to be planets but are large enough to be held together by gravity.

These disks are a window into the chemical building blocks of planets. Three categories of material make them up: dust, ice, and gas. But these materials aren’t like their Earth analogs. Dust is composed of refractory materials: materials that remain solid at high temperatures. Ice is the layer of frozen volatiles — materials that vaporize at high temperatures —that stick to the dust. The ice isn’t all water, and it doesn’t have the crystalline structure that Earth ice does, but rather an “amorphous fluffy structure” with lots of nooks and crannies. The gas is any molecule not frozen out into the ice, and the gas is at the very low temperature of ~10K [−441.67℉ / −263.15℃].

There are lots of questions about these materials that are only now able to be answered. How much of each material is present and the chemical breakdown of each material will affect the kinds, properties, and atmospheres of the resulting planets. Whether or not the planets that form will be hospitable to life is an even harder question that depends on the presence of biogenic elements (C, H, O, N, S, P), which are the building blocks for life on Earth.

The Atacama Large Millimeter/submillimeter Array (ALMA) has allowed astrochemists to measure the substructure of the composition of protoplanetary disks. The ALMA-MAPS program looked at the millimeter-size dust grains’ emissions for different molecular line data. However, ALMA is only good at looking at gas and dust, but not ice. Most volatiles are in the ice, which meant we weren’t able to constrain their properties until JWST came along.

JWST is able to observe edge-on protoplanetary disks, which allows us to measure the central star’s light as it passes through the disk. This allows us to determine the disk composition including the ice. In an early JWST observing program of the HH 48 NE disk, they found evidence for H2O, CO2, and CO, but they needed to produce spectra in the lab for comparison.

Because space ice is so different from Earth ice, Dr. Bergner’s group uses a highly specialized cryogenically cooled vacuum chamber to form analogs of space ice for study. They take spectra of samples to try and match the JWST observations. They also do full radiative transfer modeling of how the photons moved through the disk in order to properly reproduce the observations.

From this work, they were able to differentiate between possible scenarios, and found that there are different regions in the disk where H2O, CO, and CO2 all interact (“polar” regions) and regions where only CO and CO2 interact (“apolar”). They were also able to measure the C/O ratios in the icy solids and found lower values than expected based on previous protostellar ice inventories. This is only one system, of course, but this is exciting for future work. JWST has already observed or is scheduled to observe 12 edge-on disks that will allow the team to explore disks as a population.

Dr. Bergner also highlighted the need for far-infrared observations. Water’s emission line, cool-warm gas phase water lines, and gas tracing for the total disk mass are only possible with far-infrared spectra. The proposed PRobe Far-Infrared Mission for Astrophysics (PRIMA) mission is still conceptual, but if approved, it would fill in this gap.

The JWST spectra also show the presence of more complex molecules, the formation and fate of which was not known. Her group investigated excited-state oxygen atom chemistry, where ionized oxygen can react with hydrocarbons to form organic molecules. This reaction has no activation barrier, but it might not be stable. In a lab setting, Dr. Bergner’s team found that this process can make complex molecules at 10K, and that this process is broadly applicable to form many different molecules.

She then focused on what happens to these molecules once they’re formed. Making a planet is violent, and we don’t expect complex molecules to survive the formation process. It seems likely that complex molecules are delivered later through impacts by icy planetesimals. This is backed up by looking at planetesimals in our own solar system — like comets and asteroids — which also have chemical complexity that dates back to the solar system’s formation. Her group modeled the survival of ice in disks, and found that comets may form further out in the disk before drifting inward to smaller radii, which protects the ice.

2017’s visit from Oumuamua was the first time we had the opportunity to study a planetesimal from another system. It also had a big mystery — it was moving faster than we would expect under purely gravitational conditions. But it wasn’t aliens — it was likely due to outgassing (ejection) of material giving it a boost, similar to what comets are known to do. What gas it was releasing was hard to pin down. There was no evidence for carbon-based gases, and the amount of solar energy it received wasn’t enough to cause it to release water or CO2. This left a small list of possible materials.

Dr. Bergner studied hydrogen as an option. The theory was that Oumuamua was a comet coming towards us, and radiation hitting water molecules created molecular hydrogen that got trapped in the nooks and crannies of the amorphous ice. When our Sun heated the remaining water ice, it crystallized into a lattice structure and the hydrogen escaped and boosted Oumuamua’s velocity. This turns out to be a viable option for the gravitational boost, as there is a large parameter space where it would work and the amount of solar energy it received is enough to have made the ice into a lattice.

Dr. Bergner’s work sits at the intersection of observations, experiments, and theory. The field of protoplanetary disks and planetary system formation has a bright future with JWST and potentially the far-infrared PRIMA mission.

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Westerlund 1

Editor’s Note: This week we’re at the 245th AAS meeting in National Harbor, MD, 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.bsky.social on Bluesky for more coverage. The usual posting schedule for AAS Nova will resume on January 21st.

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Workshop: Strategies for Mentoring Undergraduate Researchers (by Lindsey Gordon)

This workshop came out of the Council for Undergraduate Research and Dr. Carol Hood’s work at Cal State Bernardino on programs like CalBridge. It’ll be offered again at future conferences including the American Physical Society conference. The workshop was split into two parts. In the first, small groups discussed mentoring strategies based on experiences. What makes a good mentor? What makes a bad mentor? The important takeaway was student-centered / student-driven mentoring. In the second half, the development of individual development plans was discussed, using real student examples. These plans work backwards from a goal to create a roadmap for the student’s research, and they are broadly applicable to mentorship beyond research.

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Welcome Address by AAS President, Dara Norman (NSF NOIRLab) (by Lindsey Gordon)

This year marks the 125th anniversary of AAS, and 50th AAS President Dara Norman gave opening remarks on Monday morning. She honored our colleagues who have lost their homes in the LA fires and couldn’t attend this year. (This article from the LA Times lists ways to help those affected by the fires, and the Federal Trade Commission provides guidance on how to donate safely and avoid scams.) Dr. Norman emphasized the importance of the AAS working groups, who are dealing with the rise in AI, the overwhelming numbers of applicants to astronomy graduate programs, and our carbon footprint. The 2027 summer meeting will be held fully virtually in response to members’ concerns about climate change, equity and access, and the health of our members. “This will not be your grandma’s virtual meeting,” Dr. Norman quipped. The meeting overlaps with the International Astronomical Union general assembly, which the virtual format allows flexibility for. She concluded by emphasizing the diversity of our community and the need to retain that diversity and to maintain our community.

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Fred Kavli Prize Plenary Lecture: The Terrestrial Worlds of Low-Mass Stars, Dave Charbonneau (Harvard University) (by Lindsey Gordon)

David Charbonneau is a pioneer in observations of transiting exoplanets, and in the new plenary format of taking the Q&A session two-thirds of the way through your talk when the slides fail. He and Prof. Sara Seager (MIT) won the 2024 Kavli Prize for their work on exoplanets and their atmospheres.

His work focuses on terrestrial planets: how they form their atmospheres, how those atmospheres depend on the planet and the host star, how they might lose their atmospheres, and how we might be able to detect the atmosphere and its chemical contents.

So how do we study planetary atmospheres? It turns out we can only study systems within 15 parsecs of us with stars that are ~30% the radius of the Sun. JWST and the Extremely Large Telescope are expected to be able to detect molecules in the atmospheres of planets in that range. Dr. Charbonneau described his work on the M spectral class, which covers a huge range of stellar sizes. The M-dwarf stars he cares about for this work are the ones that fall into that 30% solar radius category. However, stars at these masses are fully convective with no radiative zone. This has huge implications for the star’s magnetic and emission activity and long-term angular momentum evolution.

There are 413 stars that fit into their observing parameters. For these stars his group studied:

1. The rate of occurrence of terrestrial worlds using the transit method, of which they find 7 in that group. They then studied the sensitivity rate — did we find all the planets that are there? — by injecting fake observations for different planetary sizes and periods. From this they were able to infer the intrinsic rate of occurrence of terrestrial planets. They didn’t see large terrestrial planets or small planets that we would’ve expected to find if they were there. This led them to conclude that there is a high occurrence rate — at least one rocky planet per two low-mass M dwarfs — and the distribution of those planets’ radii peaks at 1 Earth radius.

2. The rate of occurrence of gas giant (Jupiter-like) planets using the radial velocity method. One-third of the stars in the population had no spectra, so they set out to complete the sample. The presence of Jupiter in our solar system was highly influential to the properties of our terrestrial planets; systems without such a planet may have evolved very differently. They found that essentially none (<1.5%) of the low-mass stars had a Jupiter analog, and therefore the terrestrial planets in those systems may be very different than in ours.

At this point, the presentation equipment failed. He took questions at this time, during which he told us about his favorite planet, which is a cold, rocky planet in the habitable zone around a calm star that is a great opportunity for determining if rocky planets can retain their atmospheres.

3. Characterizing the stellar magnetic activity and other properties. They found two populations of very fast and very slowly rotating stars, suggesting a rapid transition between those states. They found the flare rate of the rapid rotators is much higher than slow rotators, which could have serious implications for the survival of an atmosphere. The stellar spindown is also very mass-dependent, with larger stars spinning down faster.

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Congressman Glenn Ivey Visit (by Lindsey Gordon)

“Goddard in the house!” Congressman Glenn Ivey has represented Maryland’s 4th congressional district — which includes Goddard Space Flight Center — since 2023. He paid a visit to the exhibit hall floor on Monday morning, where he emphasized the importance of work in the sciences, particularly in the role of climate change in the recent wildfires in CA. He’s working to keep science, NASA, and Goddard moving in the right direction in what is a very exciting time in our industry.

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Press Conference: A Feast of Feasting Black Holes (by Lindsey Gordon) (Briefing video)

Witnessing the Birth of a New Plasma Jet from a Supermassive Black Hole
Eileen Meyer (University of Maryland, Baltimore County)

Dr. Meyer discussed 1ES 1927+654, a nearby “changing look” active galactic nucleus (AGN) that brightened by 100x in 2018 over the course of a few months. This is a rare event, and the system has been monitored closely across a range of wavelengths ever since. In 2022 the X-ray emission picked up, and then the radio peaked as well, 60x brighter at the peak. The radio peak suggests that AGN jets were turned on, which had never been observed before, and challenged beliefs about the on/off timescales for jets. Very Long Baseline Array observations saw the emergence of jets going 33% the speed of light. This might be the birth of a compact symmetric object, due to the initial brightness peaking resembling a tidal disruption event. | Press release

Rapidly Evolving X-Ray Oscillations in the Active Galaxy 1ES 1927+654
Megan Masterson (Massachusetts Institute of Technology)

Masterson (an Astrobiter!) discussed the same source as Dr. Meyer and highlighted its X-ray variability. The Neutron star Interior Composition Explorer (NICER) and XMM-Newton observations show a short-term periodicity around the supermassive black hole, which is rare to observe. The period has declined from 18 to 7 minutes over the past ~2 years and is stabilizing around 7 minutes. This could be due to either oscillations of the new jets, or due to an orbiting white dwarf very close to the black hole. The system is observable by the Laser Interferometer Space Antenna (LISA), which could confirm the white dwarf if it is one. | Press release

Uncovering the Dining Habits of Supermassive Black Holes in Our Cosmic Backyard with NuLANDS
Peter Boorman (California Institute of Technology)

Dr. Boorman discussed the work of the NuLANDS project, which used infrared observations to find a population of both obscured and unobscured AGN. The obscuration comes from the donut-shaped accretion disk of material being “eaten” by the black hole. Different levels of obscuration occur depending on the orientation of the donut relative to the observer. AGN are infrared bright regardless of orientation, allowing a complete sample to be found and then categorized. They found a very balanced population of ~35% heavily obscured, ~37% obscured, and ~28% unobscured AGN, which makes a great sample for future studies. | Press release

The Discovery of a Newborn Quasar Jet Triggered by a Cosmic Dance
Olivia Achenbach (United States Naval Academy) 

We’ve been navigating by the stars for millennia now, but modern methods also use radio signals for calibration. Radio systems that switch from an “off” state to an “on” state could affect these methods. Achenbach studied a system of a recently turned-on radio-bright AGN to study trigger mechanisms for new jet formation. She found a system with evidence of previous jet activity that had been recently reignited by galaxy–galaxy interactions with a tidal tail connecting the two. | Press release

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Plenary Lecture: Galaxy Evolution Eras Tour: The Formative Years of Star Formation and Supermassive Black Hole Growth, Alexandra Pope (University of Massachusetts Amherst) (by Archana Aravindan)

The AAS 245 is just another stop in Dr. Pope’s Galaxy Evolution Eras Tour! Galaxies, just like Taylor Swift, go through different eras. In this plenary talk, Dr. Pope, Professor of Astronomy at the University of Massachusetts Amherst and the chair of the Five College Astronomy Department, focuses on the formative years of galaxy growth. This period is commonly known as cosmic noon, occurring between 10 and 11 billion years ago. During this time, galaxies formed stars at a rapid rate and black holes in galaxies grew quickly.

There appears to be some correlation between the rapidly growing supermassive black holes (active galactic nuclei (AGN)) and the star formation in galaxies. This manifests itself in several scaling relations that are observed between the mass of the black hole and the mass of stars in the galaxy in which it resides. However, we still do not know how exactly the two processes correlate with each other. Dust plays an important role in our (limited) understanding of the correlations between black holes and star formation in galaxies at cosmic noon. The majority of cosmic star formation is hidden behind the dust, with observations indicating that 50–75% of AGN are in obscured dust-filled galaxies. Luckily, with JWST, we can finally pierce through the dust and look at dusty galaxies to understand the correlations!

It’s me, hi, I’m the problem!

The biggest problem (other than dust!) in understanding the correlation between star formation and black hole growth is that measurements of the black hole accretion rates and star formation rates are often not taken from the same sample of galaxies. Using the MIRI instrument on JWST, Dr. Pope and her collaborators simultaneously study the black hole accretion rate and star formation rate in the same sample of dusty galaxies at cosmic noon. AGN and star formation activity have unique spectral signatures that can be disentangled from one another, allowing measurements of both the black hole accretion rate and star formation rate in the same galaxy. Their ultimate goal is to track the galaxies as they land on the scaling relations between the mass of the black hole and the mass of the stars.

End Game?

JWST covers the mid-infrared part of the electromagnetic spectrum, and the Atacama Large Millimeter/submillimeter Array helps us understand the submillimeter wavelengths in these cosmic noon galaxies. However, the far-infrared wavelengths are not well observed and are likely holding a wealth of information about the interplay of AGN and star formation activity.  Enter the Probe far-Infrared Mission for Astrophysics (PRIMA), which is one of the two missions selected for a concept study by NASA. This far-infrared observatory will be able to measure scaling relations, redshifts, black hole accretion rates and star formation rates for nearly 60,000 galaxies. After a detailed evaluation, NASA will select one concept in 2026 to proceed with construction, for a launch in 2032. With PRIMA, Dr. Pope is hopeful that we might finally understand how black holes and stars in a galaxy co-evolve!

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Press Conference: Supernovae and Massive Stars (by Jessie Thwaites) (Briefing video)

JWST Discovery of a Distant Supernova Linked to a Massive Progenitor in the Early Universe
Dave Coulter (Space Telescope Science Institute)

Supernovae are responsible for a huge variety of astrophysical phenomena, including star formation and heavy element production. At the beginning of our universe (right after the Big Bang), the first stars began to form. These stars were “considerably different than stars today,” and their supernovae featured “gargantuan explosions,” says Dr. Coulter. Using the JADES transient survey with JWST, some of the earliest supernovae can be studied, including the case of AT 2023adsv which is at redshift 3.61when the universe was less than 2 billion years old. This study marks a major first step towards finding the earliest supernovae and studying the evolution of some of the earliest stars. | Press release (PDF)

Core-Collapse Supernovae as Key Dust Producers: New Insights from JWST
Melissa Shahbandeh (Space Telescope Science Institute)

Dust is incredibly important in astronomy; it provides the building blocks for stars and planets that eventually create our universe as we know it today. Massive dust reservoirs have recently been detected in high-redshift galaxies, leading astronomers to re-think how dust is formed in these systems. Dr. Shahbandeh describes how core-collapse supernovae, specifically Type IIN supernovae, could be the answer. By studying supernova 2005ip with Spitzer and JWST, they can study the life cycle of dust, from the supernova that spreads material throughout the system, to the new star that forms, to the formation of solar systems and planets (and maybe life!), to the cycle’s repeat when the new star goes supernova. Dr. Shahbandeh finds that supernovae are rapid dust factories, and continue to create dust, even years after explosion! | Press release (PDF)

JWST Tracks the Expanding Dusty Fingerprints of a Massive Binary
Emma Lieb (University of Denver)

Lieb discusses an interesting binary system, known as WR140, which is enriching its local environment with dust. It consists of a massive, evolved star with strong stellar winds (called a Wolf-Rayet star) and an O-star companion. They are in a highly eccentric orbit around each other, and when they pass at their nearest point (called periastron), their stellar winds collide and produce dust, “kind of like a big belch.” By taking two images of this system nearly a year apart with JWST, Lieb can study the expanding shells of dust produced by these near passes. They find that the shells are moving at nearly 1% of the speed of light, and are non-uniform, which provides clues to the dust’s formation. | Press release

Stellar Pyrotechnics on Display in Super Star Cluster
Kristina Monsch (Center for Astrophysics | Harvard & Smithsonian)

The super star clusters (SSC) are being studied by EWOCS! Not the cute fluffy characters from Star Wars, but by the EWOCS Project, which is an international team studying the star formation processes in the Westerlund 1 and 2 clusters. These clusters consist of young, massive stars (more than 100 times the mass of our Sun), and are able to ionize their surroundings. Westerlund 1 (Wd1) is nearby (4.2 kpc away), and includes massive stars at many different phases of stellar evolution. By observing this cluster in the near- and mid-infrared with JWST’s NIRCam and MIRI instruments, Dr. Monsch can pierce through the dust in these clusters to observe the stars near the center of the cluster. They can study the powerful winds from these massive stars to gain insight into how these stars form, impact their environment, and die. | Press release

A Blue Lurker Emerges from a Triple-System Merger
Emily Leiner (Illinois Institute of Technology)

While studying the cluster Messier 67, Dr. Leiner noticed something strange. Most stars in this cluster are the same age and have similar rotations, but there are a few peculiar “blue lurker” stars that rotate suspiciously fast for their age. Hubble observations of one of these stars revealed a white dwarf with a larger mass than expected for the cluster’s population orbiting the blue lurker star.

Dr. Leiner discovered that this was the remnant of a triple system, where two closely orbiting stars merged and blew their outer envelope away, leaving behind the white dwarf. This caused accretion onto the third star — the blue lurker — which sped up its rotation. Triple star systems are fairly common (around 10% of Sun-like stars are in a triple system), they are only beginning to be understood. | Press release

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Plenary Lecture: Punching Back Asteroids: The Deflection of Dimorphos by the DART Mission, Jason Kalirai (Johns Hopkins Applied Physics Laboratory) (by Bill Smith)

Everyone who takes an introductory astronomy class learns about calculating orbits of celestial bodies, but Dr. Kalirai’s talk focused on humanity’s first successful attempt to change one. He gave an overview of the DART (Double Asteroid Redirection Test) mission, a mission designed to test our capabilities to defend Earth from an asteroid that might be heading towards impact by sending a spacecraft to smash into the asteroid to see if the impact could alter an asteroid’s trajectory to miss impact.

He began with a charge for humanity: “Let’s not be like the dinosaurs!” He followed this up with an overview of the potential threat, noting that we still haven’t found many of the asteroids that could hit Earth that are big enough to result in planetary-scale catastrophic consequences, noting examples like the Chelyabinsk impact in Russia.

He began his explanation of the mission by explaining why the “D” in DART stands for “Double.” Because asteroids orbit the Sun, it would be impossible with current technology to measure the change in an orbit of one due to the impact of a spacecraft. To get around this, the DART team identified two asteroids in a binary orbit around each other. By crashing the craft into one of them, they are able to measure the impact’s effect by studying the change to the binary orbit of the asteroids, so they ultimately decided on the Didymos–Dimorphos asteroid binary system as their target.

Next, Dr. Kalirai discussed some of the unique technical challenges of the mission, including installing a CubeSat called LICIA that would deploy before impact to collect data about the impact, and the automated guiding system that was necessary for the spacecraft to the smaller of the two asteroids in the system, because it was not identifiable until the spacecraft was essentially almost there.

Dr. Kalirai then reviewed what the DART mission team learned from the impact itself. First, it slowed the orbital period of the asteroid by about a half hour, when the original goal of the mission was about 7 minutes. They measured the momentum enhancement (called a beta), which was a factor of 3.6. A beta factor of 1 indicates the amount of momentum transfer if the craft simply hit the asteroid with no ejected material, and a beta factor higher than this indicates that the ejected material from the impact further affected the asteroid’s orbit. A measurement of 3.6 was higher than anticipated, and provided an optimistic result for this technique’s ability to potentially defend Earth in the future.

A slide from Dr. Kalirai’s talk. On the left is a simulation snapshot of a DART-like spacecraft impacting a dense rocky object of similar size to the target asteroid, and on the right is an image soon after the impact of the spacecraft and asteroid.

Dr. Kalirai concluded with two main points. First, although the DART mission itself was successful, he stressed the need to find the asteroids we still don’t know about and highlighted the future Near-Earth Object Surveyor Mission. Second, he described a “table top exercise” between multiple national, state, and local agencies to simulate a potential asteroid impact on Earth. He noted that the outcome of the exercise was that, even if the technology might exist, it must still be deployed by collaboration of governments and agencies working together to do it for it to be effective.

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Plenary Lecture: Direct Observational Constraints on Planet Formation and Accretion, Kate Follette (Amherst College) (by Jessie Thwaites)

Dr. Follette’s talk focused on two of her favorite topics: direct imaging techniques for detecting exoplanets, and effectively teaching students both inside and beyond the field of astronomy. She brought those techniques to life in her talk, requiring audience participation throughout and highlighting the importance of understanding other worlds through high-contrast detections.

Dr. Follette outlined four main methods of exoplanet detection (three of which are described in this Astrobite): transit photometry, where a planet eclipses its star and causes a dip in brightness; radial velocity, where the wobble of the star indicates the presence of a planet; microlensing, where a planet passing in front of a star causes a brief increase in brightness; and direct imaging — Dr. Follette’s speciality.

As she describes, there are many reasons to love direct imaging, from the visceral satisfaction of being able to identify planets by eye in the data to the amount of information one can obtain from the technique. Direct imaging can help characterize orbits of these planets and enable detailed modeling of an exoplanet’s atmosphere through analysis of its spectrum. The planets imaged with this technique tend to be young, as young planets tend to be brighter than older planets.

This field is also rapidly developing both technology and methodology to hopefully detect exo-Earths (smaller, Earth-sized exoplanets) in the future, and to identify biosignatures in their atmospheres. Direct imaging is built on sophisticated and rapidly evolving hardware and software techniques, including adaptive optics, coronagraphy, differential imaging techniques, and post-processing algorithms. Dr. Follette has also written a tutorial for anyone interested in learning more about the field.

A slide from Dr. Follette’s talk, highlighting their method for identifying protoplanets in a disk.

To search for exoplanets, the team considered circumstellar disks, which can have a variety of substructure — some of which is likely due to the presence of exoplanets! The challenge is identifying the planet itself in the data. They optimize their selection methods on injected signals; that way, they avoid confirmation bias. They search for the planets in the wavelength range where the planets are brightest, specifically in the H-alpha line, and subtract these measurements from the main emission of the disk (shown in the above figure). With this method they are able to identify several planets in their sample! From there, they aim to translate the detected light into a physical parameter by inferring the properties of planet populations.

In the final part of the talk, Dr. Follette focused on physics education and mentorship. There are several courses in the undergraduate curriculum at Amherst College aimed at developing students’ soft skills for research, including setting goals, time management, presentation skills, and becoming more comfortable asking questions. These are important skills to help close the opportunity gaps that some students may face. Dr. Follette also emphasized the importance of normalizing struggling (which happens to everyone!) and celebrating non-linear career paths, as well as non-astronomy or non-academic paths for students.

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banner announcing the 245th meeting of the American Astronomical Society

This week, AAS Nova and Astrobites are attending the American Astronomical Society (AAS) winter meeting in National Harbor, MD.

AAS Nova Editors Kerry Hensley and Susanna Kohler and AAS Media Fellow Lexi Gault will join Astrobites Media Intern Lindsey Gordon and Astrobiters Archana Aravindan, Bill Smith, and Jessie Thwaites to live-blog the meeting for all those who aren’t attending or can’t make it to 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 Bluesky at astrobites.bsky.social for more meeting content.

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! You can also find Kerry, Susanna, and Lexi at the press conferences Monday through Thursday. AAS press conferences are open to all, and they can also be viewed on the AAS Press Office YouTube channel for anyone not attending the meeting.


Sessions Organized by and Recommended by Astrobiters

The Astrobites crew recommends the National Osterbrock Leadership Program splinter session. This session, titled “Deepening Broader Impacts: Mentorship, DEI, and Career Advancement” (link takes you to the listing in the meeting program; must be logged in for the link to take you to the right place), will be held Tuesday, 14 January, from 10:30 am to 12:00 pm in room Chesapeake 7-8. This splinter session will feature several presentations as well as an interactive workshop, with a focus on deepening broader impacts, strengthening NSF proposals, and acquainting attendees with the National Osterbrock Leadership Program.

We are excited to share that the League of Underrepresented Minoritized Astronomers (LUMA) will be celebrating its 10-year anniversary in 2025 through an AAS Splinter Session titled “IlLUMAnating Conversations” on Wednesday, 15 January 2025, from 9:30 am to 5:00 pm ET. This splinter session will be open to ALL people of color of ALL career stages, not only to LUMA members, so please share with your networks! However, we do ask you kindly fill out this form to confirm your attendance and RSVP as this is a private event by invitation only.

LUMA is a peer mentoring community for Black, Indigenous, and Latinx women across all career stages in the space sciences. Our goal is to provide a safe, supportive virtual community where you can belong and shine. The IlLUMAnating Conversations session marks our 10th anniversary as an organization, and we are celebrating by coming together at AAS 245 for a series of workshops, talks, and community bonding activities for both current members and others in the AAS community interested in attending.

Our morning session will focus on learning how to identify, leverage, and grow your unique skills to benefit your career. We will reconvene after lunch for an afternoon session to explore ways to build deeper relationships within your community and advocate effectively for yourself and others. If you’re looking to make new friends, find a conference buddy, or learn new skills, please join us! You also can attend either the morning or afternoon session, or attend both sessions if you’d like to get more out of it! We will be having a day full of inspiring talks and meaningful workshops to equip you to succeed in your careers and effect change in your communities!

Finally, you can read the currently published AAS 245 keynote speaker interviews here. Be sure to check back all week as the remainder are released!

banner announcing the 245th meeting of the American Astronomical Society

AAS 245 is nearly here! The AAS Publishing team looks forward to connecting with meeting attendees at the upcoming winter AAS meeting in National Harbor, MD, and we’re excited to share a preview of upcoming publishing-related events. Attending the meeting will be Kerry Kroffe (AAS Director of Scholarly Publishing), Ethan Vishniac (AAS Journals Editor in Chief), Gus Muench (AAS Journals Data Editor), and Greg Schwarz (AAS Journals Data Editor). Several of the scientific editors of the AAS journals, including Frank Timmes (Associate Editor in Chief and Lead Editor of the High Energy Phenomena and Fundamental Physics research corridor) and Mubdi Rahman (Scientific Editor for the Laboratory Astrophysics, Instrumentation, Software, and Data research corridor), will be in attendance as well. Be sure to stop by the AAS booth in the Exhibit Hall to say hello, chat about the journals, have your data questions answered, and pick up some swag!

AAS Nova Editors Kerry Hensley and Susanna Kohler, AAS Media Fellow Lexi Gault, Astrobites Media Intern Lindsey Gordon, and the rest of the Astrobites team will also be available periodically at the Astrobites booth in the Exhibit Hall. We look forward to seeing you there!


Data Editors Help Desk

AAS Journals Data Editors Gus Muench and Greg Schwarz will be staffing a data help desk during AAS 245. Please drop by the AAS Publications stand in the main AAS booth to hear more about upcoming changes to AASTeX (v7!), or to discuss best practices for data and software publication in the AAS journals. Gus and Greg are looking forward to your tough data questions!


Open Science at AAS 245

Note: The links in this section take you to the corresponding entries in the AAS 245 block schedule. You must be logged in for the links to work correctly; otherwise, they will take you to the main block schedule page.

On Monday, there is an exciting splinter session from 10:00 am to 12:00 pm titled “ExoCore: An Open Science Curriculum for Enhanced Reproducibility and Equity in Exoplanet Research.” The intended audience ranges from students and postdocs working on exoplanet research to those interested in the ethos and methods of open science in general. The session will include presentations, a guided discussion, and a hands-on tutorial. This session takes place in National Harbor 8.

On Wednesday from 2:00 to 3:30 pm, NASA is hosting a special session (#347) on “Open Science: NASA Astrophysics in the Roman Era.” This session focuses on new initiatives to facilitate the sharing of data and computational resources across NASA as new missions like Roman move data storage and analysis on to cloud-based science platforms. This session will be held in Chesapeake 4-5.

We also want to draw your attention to a special session (#425) on Thursday morning from 10:00 to 11:30 am. “The Power of Collaborative Networks in the Era of Big Data” will use presentations and a moderated discussion to explore the importance of collaborative networks to doing science in the current era of big data. Collaborative networks, which can be anything from citizen science teams to international science communities, will be critical to making best use of incoming massive datasets, such as the one that will be generated by the Vera C. Rubin Legacy Survey of Space and Time. This session will be held in Chesapeake 4-5.

banner announcing the 175th anniversary of the Astronomical Journal

The first issue of The Astronomical Journal (AJ) was published 175 years ago this month. This remarkable history means that the journal has persisted through the American Civil War and both World Wars, through 35 presidential administrations, and even through the development of “astronomer” as a profession in North America — it wasn’t until 50 years after the AJ’s launch that the continent founded its first professional society of astronomers, the American Astronomical Society.

As the first astronomy-focused academic journal to be published outside of Europe, the AJ has come a long way: its first issue — containing just a single printed article (“Development of the Perturbative Function of Planetary Motion”) — would have had limited circulation among the small but growing community of North Americans interested in astronomy. Now, as a fully open-access electronic journal, the AJ garners more than 100,000 views per year.

Early issues of the journal presented major advances in solar system and stellar science, laying the groundwork for modern discoveries in these fields. In the pages of the AJ, you can find foundational work establishing the ubiquity of black holes in the centers of galaxies, an examination of the iconic Hubble Deep Field, and Nobel-prize-winning evidence for the accelerating expansion of the universe, to name just a few works. Today, impactful observational results can be found alongside major advances in instrumentation, surveys, and software, such as the Wide-Field Infrared Survey Explorer, the Sloan Digital Sky Survey, and the astropy codebase.

To celebrate this remarkable milestone, we invite you to join us in looking back on the journal’s history using this interactive timeline. Here’s to 175 more years!

Io with a volcanic plume

Editor’s Note: This week we’ll be writing updates on selected events at the 56th Division for Planetary Sciences (DPS) meeting happening in Boise, Idaho, and online. The usual posting schedule for AAS Nova will resume on October 14th.

Table of Contents:


The Open-Source Science Initiative at NASA (J.L. Galache)

J.L. Galache (Agile Decision Sciences, NASA HQ) opened the session with a brief primer on open-science initiatives at NASA. Essentially, open science is the act of making your data, software, and publications freely accessible to all. Open science benefits the planetary science community by lowering barriers to entry and enhancing reproducibility of research. (Of course, open science also benefits you because your freely accessible data and publications will be cited more often!) NASA approaches open-science implementation through funding (sunpy and astropy have received funding from NASA, among many other recognizable names in science software), training, and policy. Current policy states that data and software should be made available at the time the research is published, and publications should be made available through a pre-print server (e.g., arXiv) if not being published in an open-access journal. Among the existing training options is Open Science 101, an online training module through which 1,900 people have already been accredited.

Return to Table of Contents.


Digging Deep: Unveiling Vertical Mixing and the Core Mass of Giant Exoplanets with JWST (David Sing)

David Sing (Johns Hopkins University), winner of the 2024 Alexander Prize for outstanding contributions that have significantly advanced our knowledge of planetary systems, described the journey to understanding exoplanet atmospheres and interiors from Hubble to JWST. Sing focused on the transit method, which has enabled the discovery of thousands of planets beyond our solar system and increasingly allows scientists to probe the atmospheres of those worlds.

With Hubble, scientists were able to test their models of photochemical equilibrium in exoplanet atmospheres, which predicted broad compositional trends with planet temperature. Hubble observations confirmed the basic picture of the chemical composition of hot Jupiters while also revealing complexities like clouds and hazes, which make it difficult to extract chemical abundances from spectra, and the presence of disequilibrium chemistry, which required extra attention from modelers.

plot of mass–metallicity relationship for planets and exoplanets

The mass–metallicity relationship for solar system planets (black points) and exoplanets (colored points). Click to enlarge. [From slide by David Sing]

Hubble observations raised further questions about giant planets, such as the state of their chemical disequilibrium, vertical mixing, horizontal mixing, and even their formation mechanism. Giant planet formation can be probed by measurements of planetary core mass fraction, with the core accretion model predicting that giant planets have roughly 10-Earth-mass rocky cores. In addition, the core accretion model predicts that as a planet’s mass increases, its overall metallicity decreases due to the accumulation of a massive envelope of hydrogen and helium. The giant planets in our solar system follow the predicted relationship, but the evidence for gas giant exoplanets is less clear. What can JWST tell us about the lingering issues in giant planet formation, chemistry, and mixing?

JWST spectrum of WASP-39b

JWST spectrum of WASP-39b’s atmosphere and best-fitting model. [From slide by David Sing]

Enter the JWST Transiting Exoplanet Community Early Release Science Program, which aimed to provide science results from phase curve, primary transit, and secondary eclipse observations of exoplanets while testing and leading to a greater understanding of the capabilities of JWST instruments. Sing highlighted the results of JWST transit observations of WASP-39b, which showed a prominent spectral feature from carbon dioxide (not seen by Hubble) as well as a feature at 4 microns that wasn’t predicted by models. This feature belonged to SO2, showing the first sign of photochemistry in an exoplanet. (SO2 is produced through the reaction of H2S with water molecules that have been split apart by starlight.)

Sing also described the important results from JWST observations of two other exoplanets, HAT-P-18b and WASP-107b. These are both cool/warm gas giants that are expected to have methane in their atmospheres. HAT-P-18b showed no sign of methane in its atmosphere — since the molecule is expected to exist, does this mean it’s being destroyed by photochemistry or by mixing into the deep, hot atmosphere of the planet?

Observations of WASP-107b provided more clues: in addition to CO2 and water, JWST observations of WASP-107b showed at last a hint of methane. However, there was about a thousand times less methane than expected given the planet’s temperature. By modeling both vertical mixing and photochemistry, Sing’s team showed that the methane depletion was due to mixing. Going further with these data, they used interior structure modeling to estimate the mass of the core at 11.5 Earth masses — consistent with predictions of the core accretion model.

Up next is the exoplanet grand tour spectroscopic survey, which will observe 25 exoplanets during 125 hours of JWST time. Stay tuned for news from this survey — the first data are being collected roughly 24 hours after this talk!

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Tracing the Heating of the Solar System Through Geochemical Signatures (Katherine de Kleer)

Katherine de Kleer (California Institute of Technology), winner of the 2024 Harold C. Urey prize for outstanding achievements in planetary science by an early-career scientist, described recent work on the history of heating in the solar system. De Kleer and collaborators use the Atacama Large Millimeter/submillimeter Array (ALMA) to understand where, when, and how objects in the solar system were heated and how that drives the chemical evolution of and geological activity on those objects today.

Let’s take things all the way back to the early days of the solar system: in the beginning, there was aluminum-26, a once-abundant, radioactive form of aluminum that heated the infant solar system. Heating from aluminum-26 melted early planetesimals and caused them to differentiate, separating into distinct compositional layers. Some of these planetesimals clumped together to form what are today the planets in our solar system, while others collided, leaving their remains scattered through the solar system as asteroids. The fragments of planetesimals in the asteroid belt can tell us about differentiation and, thus, heating in the protoplanetary disk that birthed our solar system.

thermal emission from asteroid Psyche

The thermal glow of asteroid 16 Psyche as seen by ALMA. [From slide by Katherine de Kleer]

Using ALMA, de Kleer observed the thermal emission from large main-belt asteroids — with an incredible resolution of 30 kilometers — and modeled the observations. The data show high emissivity (indicative of large metal content) but low polarization (indicative of scattering due to metal inclusions). This suggests that rather than having metal tied up in minerals, the metal in these asteroids likely exists in the form of numerous metallic chunks.

While heating is still ongoing in the solar system today, radiogenic heating — heating from the decay of radioactive material — is not as important as it once was. Now, small bodies are largely heated through tidal heating. The most dramatic example of the effects of tidal heating is Jupiter’s moon Io — the most volcanically active body in the solar system. Tidal heating melts Io’s rocky interior, which then gushes through the moon’s 400 active volcanoes to its surface.

Many images of Io and its volcanoes

Many views of the infrared glow of Io and its many volcanoes. Wavelength increases toward the bottom. Click to enlarge. [Slide by Katherine de Kleer]

By studying when and where Io’s volcanoes erupt, de Kleer’s team hopes to learn about Io’s interior, including where tidal heating is deposited. Tidal heating models predict specific distributions of Io’s volcanoes, but after 300 nights of observing Io (covering many revolutions around Jupiter), there doesn’t appear to be any cyclical behavior to the eruptions, nor does the spatial distribution appear to match the models well. This could mean that convection in Io’s mantle is obscuring the signature of tidal heating, or there could be stochastic geological processes at play.

Scientists have studied volcanic activity on Io for forty years, but the moon has been active much, much longer. If Io has been trapped in a resonance with fellow moons Europa and Ganymede for billions of years, as research suggests, it must have lost the equivalent of its entire mantle contents many times over, churning through and reprocessing this mantle material repeatedly. Another way of looking at Io’s evolution over time is through its atmosphere. Sulfur — an abundant component of Io — is lost to space from the moon’s upper atmosphere. Because different isotopes of sulfur have different masses, lighter isotopes are held less tightly to the moon and are preferentially removed from the atmosphere. By measuring the ratio of different isotopes of sulfur, de Kleer showed that Io has lost 94–99% of its available sulfur, supporting the picture of a dramatically, dynamically heated and evolving world.

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JWST image of Uranus and its moons

Editor’s Note: This week we’ll be writing updates on selected events at the 56th Division for Planetary Sciences (DPS) meeting happening in Boise, Idaho, and online. The usual posting schedule for AAS Nova will resume on October 14th.

Table of Contents:


Plenary Lecture: Addressing Mental Health in Planetary Science: Big and Small Steps to Creating an Environment that Supports Well-Being (David Trang)

Planetary scientist and mental health counselor David Trang (Space Science Institute) discussed the results of recent surveys of mental health among planetary scientists and strategies to improve the health of the community. Mental health is a pressing issue for our community: 76% of planetary scientists surveyed reported having anxious or depressive symptoms that made it at least somewhat difficult to perform work duties, take care of things at home, or get along with others. Twenty-nine percent of respondents found these tasks difficult, while 9% of respondents said they found these tasks very difficult.

These issues affect everyone: even if you’re not personally experiencing symptoms, the collaborative nature of planetary science means that someone you work with likely is. Distracting thoughts associated with anxiety, stress, and depression occupy short-term memory, affecting research quality, the ability to develop new ideas, interpret data, and more. Aside from research quality, poor mental health worsens physical and social health as well.

results of survey of anxiety among planetary scientists

Prevalence of clinically significant anxiety among planetary scientists in 2022 and 2023. Rates are compared against the general population during (red line) and before (green line) the COVID pandemic. Click to enlarge. [Slide by David Trang]

To examine the mental health of our community, Trang surveyed roughly 300 planetary scientists in 2022 and 2023, using common anxiety, stress, and depression assessments. The survey indicated higher than average anxiety and depression among female, POC, LGBTQ+, and early career respondents. Notably, graduate students had the highest prevalence of anxiety and depression of any of the groups surveyed. While stress, anxiety, and depression decreased for nearly all demographic groups in 2023 compared to 2022, even after decreasing to 2023 levels, planetary scientists across the board remained more stressed, anxious, and depressed than the average respondent from the general public, pre-COVID. For almost all groups, levels remained higher among planetary scientists in 2023 than the general population during the peak of COVID.

Overall, the results show a statistically significant difference in the prevalence of anxiety, stress, and depression between members of marginalized groups and members of non-marginalized groups. While this difference may reflect larger cultural and societal issues, it also presents an opportunity for planetary science participation to become a protective factor against these larger issues.

survey results showing differences in depression and anxiety between mission participants and non-participants

Prevalence of clinically significant anxiety and depression among mission participants (purple) and non-participants (blue). The white shapes indicate statistically significant results. Click to enlarge. [Slide by David Trang]

In what way might the planetary science community be protective? As an example, Trang showed that there are statistically significant differences in the prevalence of anxiety and depression between scientists that participate in missions and those that do not. Why mission participation has a protective effect isn’t yet clear, but Trang hypothesized that mission participation creates a sense of belonging to a group, and it also pairs early career scientists with a larger number of potential mentors, increasing the chances of there being a positive mentor relationship. (During the Q&A, audience members proposed other potential factors, such as stability of funding and the impact of working toward a common goal.)

To bring these positive aspects of mission participation to all planetary scientists, Trang suggested creating more teams (not just missions, but research institutes and interest groups as well) and improving mentorship for early career scientists. To achieve the latter goal, institutions could implement mandatory mentorship training for graduate advisors or invest in a mentor advisor to provide career mentorship to a large number of graduate students, reducing the burden on graduate research advisors.

plot of top contributors to depression

Top contributors to depression. Click to enlarge. [Slide by David Trang]

In addition to these larger policy changes, individuals can make small changes that have a big impact. One area of focus is expressing appreciation, as many of those surveyed said that not feeling appreciated was a major contributor to their anxiety or depression. Trang suggests that simply saying thank you with one sentence explaining why you’re grateful can go a long way. And as someone receiving an expression of appreciation, be sure to say how you felt about it (e.g., “You’re so welcome, I’m happy to hear that you found it helpful!”) — this makes it a positive experience for everyone involved.

Trang presented two other strategies that can help people feel appreciated: focusing on strengths and complimenting the process. As scientists — especially scientists in advisor roles — it’s easy to focus on what’s wrong and what needs improvement. For example, when editing a student’s manuscript, it’s natural to point out what needs to be fixed. But don’t forget to focus on what’s been done well (e.g., “You did a great job of reviewing past work in the introduction. Let’s bring that same strategy to the discussion section.”). Similarly, it’s easy to congratulate or compliment someone after a major achievement — say, being awarded a grant — so try to compliment the steps of the process as well. For example, take the time to acknowledge the hard work that went into writing an excellent proposal, even if it wasn’t selected.

Want to implement these changes in your life? Set SMART goals, Trang suggests. Give yourself a Specific, Measurable, Achievable, Relevant, Time-bound goal, such as pointing out two strengths each time you review a paper this year. Through individual efforts and broad policy changes, we can make the planetary science community a healthier place.

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Press Conference: Amy Simon, Richard Cartwright, Mariah Jones (Briefing video)

First to speak was Amy Simon (NASA’s Goddard Space Flight Center), who presented results from a long-term study of Jupiter’s Great Red Spot. The famous Great Red Spot is the largest storm in the solar system, spanning 10,000 miles (~16,000 km). Although it’s been a constant feature of Jupiter’s disk for centuries, it’s both steadily shrinking and changing in more subtle ways. Simon’s team used the Hubble Space Telescope to investigate the Great Red Spot’s 90-day oscillations, which are periodic changes in the rate at which the storm drifts westward. This rate oscillation is seen in historical and ground-based data. The Hubble observations showed that many aspects of the spot varied over the course of 90 days. The spot’s semimajor axis varied, though it’s north–south extent did not, and the height and width of the deep-red core changed.

Great Red Spot with regions labeled

Regions of Jupiter’s Great Red Spot. [From slide by Amy Simon]

All of these changes were roughly in phase with one another. Other changes, such as changes to the reflectance of the core of the spot and the collar region just outside the core, were out of phase with each other. Some parameters were also correlated, such as the spot’s size and speed; the spot is largest when it is moving most slowly. The core is also brightest when the spot is largest, although this change is small. An analysis of the wind velocity field showed that the surrounding velocity isn’t compensating for the other oscillations. This indicates that a simple two-dimensional model in which changes in vorticity balance the oscillations doesn’t apply to this system, and the three-dimensional atmospheric structure must be more complex.

Uranus's moon Ariel

Ariel as seen by Voyager 2 in 1986. [NASA/JPL]

Next, Richard Cartwright (Johns Hopkins University Applied Physics Laboratory) brought things farther out in the solar system with new JWST observations of Ariel, the fourth-largest moon of Uranus. The JWST data revealed the presence of CO2 and CO ice on the moon’s surface. This finding is intriguing because these materials likely escape to space over time, so they must be replenished somehow. CO2 ice might form via irradiation of materials on the moon’s surface by energetic particles trapped in Uranus’s magnetosphere. The alternative, which is favored by the JWST data, is that CO2 gas could escape from a reservoir below the surface and condense on the surface.

JWST spectrum of Ariel

JWST observations of Ariel. The spectra show clear signals from CO2, CO, and H2O, plus a tentative hint of CO3. Click to enlarge. [From slide by Richard Cartwright]

A potential reservoir could be a subsurface ocean rich in CO2, CO, and possibly CO3. If CO3 were to be found on Ariel’s surface, that would be strong evidence for the presence of such an ocean, since it’s a difficult compound to make on the surface of an airless body. The JWST data show a tiny hint of a CO3 feature as well as a feature that could be interpreted as being due to clathrates — chemical lattices that trap molecules. Both of these features, if confirmed, would provide firm evidence for the subsurface ocean hypothesis. Curiously, the data show no hint of hydrogen peroxide, which has been seen on the moons Europa, Ganymede, Enceladus, and Charon. This might hint that the radiation environment at Ariel is quieter than expected.

Future work will dive deeper into new JWST observations of Uranian moons Umbriel, Titania, and Oberon. Preliminary analysis of the JWST spectra shows the first evidence of CO ice on these worlds.

simulation results for simulated co-orbitals in exoplanet systems

Comparison of the results for TRAPPIST-1 (top), a resonant system, and Kepler-90 (bottom), a non-resonant system. More of the synthetic co-orbitals remained in stable configurations in the Kepler-90 system. Click to enlarge. [From slides by Mariah Jones]

Finally, Mariah Jones (Vassar College/SETI Institute) took things out of the solar system altogether with a theoretical exploration of co-orbiting bodies in exoplanet systems. Co-orbitals are bodies that share an orbit. For example, the Jupiter trojan asteroids share Jupiter’s orbit. Trojans are a class of co-orbitals that sit 60 degrees in front of and 60 degrees behind a planet. Horseshoes are co-orbitals with a more complex configuration, librating around 180 degrees from their host planet. In our solar system, Mars, Jupiter, and Neptune host stable populations of co-orbiting bodies, but Saturn and Uranus do not. The reason for this may be that Saturn and Uranus are both in near-resonance with Jupiter and Neptune, respectively. Orbital resonance refers to a setup in which the orbital periods of two or more bodies are integer multiples of one another.

Jones and collaborators used dynamical modeling to investigate if the presence of resonance in a planetary system affects the long-term stability of co-orbital populations. They collected initial conditions for several multi-planet systems from the NASA Exoplanet Archive and injected 20 synthetic co-orbitals into each system. They found a variety of behaviors, including stable trojans and horseshoes, no stable solutions, or switching between stable trojan and horseshoe configurations. They found that stable configurations were more likely for systems without resonance. This trend might happen because in a resonant system, bodies that are co-orbital with one planet are also in resonance with another planet, destabilizing the configuration.

Slides from these three presentations are available in the press kit.

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Titan and Saturn

Editor’s Note: This week we’ll be writing updates on selected events at the 56th Division for Planetary Sciences (DPS) meeting happening in Boise, Idaho, and online. The usual posting schedule for AAS Nova will resume on October 14th.

Table of Contents:


Plenary Lecture: Planetary Habitability in the Solar System and Beyond (Stephen Kane)

What is planetary habitability? This deceptively simple question posed by Stephen Kane (University of California, Riverside) is surprisingly controversial. Kane defines the answer as an assessment of the energy balance at a planet’s surface and what influences that balance over time. When looking at the vast sample of exoplanets — nearly 6,000 are currently known — Earth-size planets are common, opening up the possibility that the circumstances necessary for habitability are common as well.

image of Venus featuring swirling clouds

Venus as seen by the Mariner 10 spacecraft. [NASA/JPL-Caltech]

But the problem is a tricky one. Take Venus, for example. To a distant observer, Venus and Earth are both “Earth-like” planets, but only Earth is habitable today. The differences between the two are many — Venus is 30% closer to the Sun and receives twice the solar flux, and it also lacks a moon, rotates extremely slowly and nearly perfectly upside down, lacks a magnetic field, and lacks plate tectonics — but it’s not yet clear which of these properties are responsible for the hellish conditions on Venus today. Time is also an important factor: as recently as a billion years ago, Venus may have had surface water.

Water is a recurring theme in discussions of habitability, since one framework within which to assess a planet’s energy balance is whether a planet is able to sustain liquid water on its surface. This framework is reasonable — and not unreasonably Earth-centric — because water is common throughout the universe, it’s a solvent in which biochemical reactions can take place, and it remains liquid up to (relatively) high temperatures, allowing chemical reactions necessary for life to proceed quickly.

graphic listing the many factors important for planetary habitability

The multitude of factors that could impact planetary habitability. What this graphic doesn’t show — and what’s critical to find out — is the relative importance of these factors and the connections between them. Click to enlarge. [Slide by Stephen Kane; originally from Vicky Meadows and Rory Barnes]

There are many interconnected factors that play a role in determining a planet’s energy balance, and it’s challenging to understand which are most important. To approach this problem, Kane suggests using the “statistical hammer” of exoplanets and taking cues from our own solar system’s evolutionary history. As an example of what we can learn from our own solar system, Kane pointed to Mars, which has an interesting habitability history. Mars has been examined closely by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission for a decade, and MAVEN measurements show that Mars once had a surface pressure similar to present-day Earth. Today, Mars has lost much of its atmosphere, rendering the planet cold and dry.

Atmospheric loss is important when considering exoplanets as well. In the TRAPPIST-1 system, which is famous for containing seven terrestrial planets, three or four of which are in their star’s habitable zone, recent JWST observations suggest that the two planets closest to the star have little to no atmosphere. (A hazy or cloudy atmosphere is possible for TRAPPIST-1 c, but TRAPPIST-1 b is extremely unlikely to have any kind of atmosphere.)

Another consideration for exoplanetary systems is the presence or absence of giant planets. Our solar system may be unusual among planetary systems because it contains four giant planets beyond the snow line (the distance from the Sun at which water exists as ice). Many other known exoplanet systems contain giant planets closer to their stars, which may prevent Earth-size planets from attaining stable orbits in the habitable zone. However, a well-placed giant planet may be critical for the habitability of Earth-like planets; giant planets positioned beyond the snow line can transport volatiles (critically, water ice) into the inner solar system. While Jupiter has a nearly circular orbit, researchers see giant planets beyond the snow line with a wide range of orbital eccentricities — and it turns out that giant planets with more elliptical orbits are actually better at scattering volatiles toward would-be Earths.

In the conclusion, Kane added a rather somber comment about the challenge of assessing planetary habitability: modeling suggests that the three biggest factors determining Venus’s current uninhabitability are the incident solar flux, Venus’s slow rotation rate, and its lack of plate tectonics. A distant observer could easily pin down the first of those three factors, but the other two are difficult or impossible to determine from afar.

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Plenary Lecture: From Venus to Exoplanets and Back Again (Cedric Gillmann)

Cédric Gillmann (ETH Zurich) brought the discussion back to Venus in the second talk of the session. Seen from afar, it would be very difficult to distinguish Venus from Earth because the two planets have similar basic properties. This fact led Venus to be a prominent target of early solar system exploration, with some observers expecting Venus to be a sort of warm and humid “space Florida.” Instead, images from the surface revealed Venus to be dry and lifeless, though more Earth-like than it seemed at first glance: the images showed basaltic (composed of volcanic rock) plains similar to those found on Earth.

That might be where the similarities between Venus and Earth end. Though Venus and Earth both have volcanoes, the type and distribution of volcanic features is dissimilar, suggesting that something in Venus’s interior is markedly different from Earth’s. Venus also has a staggeringly high surface pressure (more than 90 times Earth’s surface pressure) and temperature (hot enough to melt lead) and an atmosphere rich in carbon dioxide, with some nitrogen and just a trace of water.

Comparison of known Venus zone and habitable zone planets

Comparison of known Venus zone and habitable zone planets. [Slide by Cédric GIllmann]

Much remains unknown about Venus. Observations suggest that the planet has lost much of its atmosphere, but it’s not yet clear how much was lost and when. Luckily, several missions to Venus are in preparation that will help researchers learn more about our neighboring planet — and about exoplanets as well. Given the bias toward finding short-period exoplanets, we know of more planets in the “Venus zone” than in the habitable zone. By studying Venus, we can learn more about these Venus-zone exoplanets that we’ll never be able to observe at close quarters.

This is just one example of how exoplanet studies increasingly benefit from solar system studies. Certain factors, especially those related to planetary interiors, can never be measured directly for exoplanets but can be investigated for solar system planets. Gillmann pointed to the mantle as an especially important factor; as a planet’s mantle evolves, it affects the planet’s core and cools the planet. It also affects volcanism, which in turn affects the planet’s atmosphere, making it central to the planet’s overall evolution.

In summary, Venus represents a planet whose evolutionary history is likely complicated and is still uncertain, though upcoming missions like EnVision and VERITAS should help to illuminate its past. By studying the relatively accessible Venus, astronomers can learn more about planets that we’ll never get to see up close.

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Plenary Lecture: ExoTitans: Connecting Solar System and Exoplanet Studies (Kathleen Mandt)

In the final talk of the session, Kathy Mandt (NASA’s Goddard Space Flight Center) took the habitability discussion in a colder direction, whisking the audience to the ocean worlds of the outer solar system. Our solar system contains several moons with liquid oceans beneath their icy surfaces. The Europa Clipper mission, which is scheduled to launch no sooner than 12 October, will explore one of these ocean worlds in detail.

Ocean worlds are an enticing place to look for life beyond Earth, but it’s exceedingly difficult to study the oceans directly. It’s unknown how thick the ice shells may be, and even drilling through antarctic ice on Earth is difficult. This means that studying the subsurface ocean on an exoplanet will be beyond our reach. Is there an easier way to study exoplanet ocean worlds?

Titan's polar seas

Radar image of Titan’s north polar seas. [NASA/JPL-Caltech/ASI]

Saturn’s largest moon, Titan, may be the best place to start to learn about exoplanet ocean worlds. Titan has a thick atmosphere composed mainly of nitrogen and methane, which react to form complex hydrocarbons and nitriles, creating haze. It also has a multitude of lakes and seas filled with a freezing, oily mixture of liquid methane and ethane. There are 130 recorded flybys of Titan by the Cassini spacecraft, providing ample data to compare to exoplanet observations.

Titan-like exoplanets are likely to be common, but our current detection capabilities limit the number of candidate exo-Titans — because these planets must be cold, they must be located farther from their stars, making them harder to detect with the transit method.

illustration of the TRAPPIST-1 planets

An artist’s rendition of the seven known planets in the TRAPPIST-1 system, based on data taken through 2018. [NASA/JPL-Caltech/R. Hurt, T. Pyle (IPAC)]

One candidate exo-Titan is TRAPPIST-1 h, the outermost of the known TRAPPIST-1 planets. Based on its bulk density, TRAPPIST-1 h’s water-to-rock ratio is higher than Earth’s but lower than Titan’s, placing it somewhere around Europa. TRAPPIST-1 h may have cryovolcanoes, and climate modeling shows that while it’s too warm for liquid methane — a critical component of Titan’s hydrocarbon seas — it’s the right temperature for liquid ethane.

If TRAPPIST-1 h is an exo-Titan, what would JWST enable us to learn about its atmosphere? Mandt’s team performed atmospheric modeling of exo-Titans to estimate what JWST would see when looking at such a planet. They found that it was often difficult to back out the input properties of a planet since there was a lot of degeneracy between temperature and pressure. Some factors, such as eddy diffusion, were impossible to discern at JWST-accessible infrared wavelengths but could be probed by an ultraviolet telescope.

Next, Mandt’s team plans to incorporate more complex photochemistry in their model, which will likely be challenging. TRAPPIST-1 is an M dwarf, which means that the star is variable at the X-ray and ultraviolet wavelengths that drive chemical reactions.

Ultimately, Mandt emphasized the importance of planetary scientists and exoplanet scientists working together, leveraging past knowledge from Cassini and upcoming insights from the Dragonfly mission to interpret observations of exo-Titans and other ocean worlds.

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