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.

Table of Contents:

• Bronze Award for the University of Michigan from the Physics and Astronomy SEA Change Committee
• 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.)
• Press Conference: Black Holes & New Outcomes from the Sloan Digital Sky Survey
• Henry Norris Russell Lectureship: The Cosmic Triangle: Probing the Dark Side of the Universe, Neta A. Bahcall (Princeton University)
• Press Conference: New Information from Milky Way Highlights
• Plenary Lecture: A Detector Backstory: How Silicon Detectors Came to Enable Space Missions, Shouleh Nikzad (Jet Propulsion Laboratory)
• Plenary Lecture: Annie Jump Cannon Prize Lecture: The Icy Origins of Planetary Systems, Jenny Bergner (University of California, Berkeley)

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.

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]

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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)

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

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.

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]

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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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.

Table of Contents:

• Workshop: Strategies for Mentoring Undergraduate Researchers (From Sunday, 12 January)
• Welcome Address by AAS President, Dara Norman (NSF NOIRLab)
• Fred Kavli Prize Plenary Lecture: The Terrestrial Worlds of Low-Mass Stars, Dave Charbonneau (Harvard University)
• Congressman Glenn Ivey Visit
• Press Conference: A Feast of Feasting Black Holes
• Plenary Lecture: Galaxy Evolution Eras Tour: The Formative Years of Star Formation and Supermassive Black Hole Growth, Alexandra Pope (University of Massachusetts Amherst)
• Press Conference: Supernovae and Massive Stars
• Plenary Lecture: Punching Back Asteroids: The Deflection of Dimorphos by the DART Mission, Jason Kalirai (Johns Hopkins Applied Physics Laboratory)
• Plenary Lecture: Direct Observational Constraints on Planet Formation and Accretion, Kate Follette (Amherst College)

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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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!