AAS 246: Day 3

Editor’s Note: This week we’re at the 246th AAS meeting in Anchorage, AK, 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 June 16th.

Table of Contents:

• • Plenary Lecture: The Hubble Space Telescope at 35: Eyeing the Future, Jennifer Wiseman (Goddard Space Flight Center)
  • Press Conference: Recent and Upcoming Discoveries in the Broader Universe
  • Plenary Lecture: Advancing Exoplanet Characterization: Five Years of High-Resolution Spectroscopy with KPIC, Dimitri Mawet (California Institute of Technology)
  • Donald E. Osterbrock Book Prize Lecture: Where Are We? How Past Astronomers Found Their Place in the Universe — and on Earth, Seb Falk (University of Cambridge)
  • Plenary Lecture: Things in Disks: Towards a New Understanding of Galactic Nuclei, K.E. Saavik Ford (CUNY Borough of Manhattan Community College/American Museum of Natural History)

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Plenary Lecture: The Hubble Space Telescope at 35: Eyeing the Future, Jennifer Wiseman (Goddard Space Flight Center) (by Margaret Verrico)

Wednesday started bright and early with a plenary talk by Hubble Space Telescope Senior Project Scientist Jennifer Wiseman. AAS Vice President Grant Tremblay opened the talk with a story about seeing comet Shoemaker–Levy 9 impact the planet Jupiter on the news, an event that was imaged with Hubble and that he said influenced his decision to pursue astronomy. It was an appropriate anecdote to start the celebration of Hubble’s 35th year in orbit, which Dr. Wiseman credited with opening many new worlds in astronomy.

Dr. Wiseman began by describing how our science community has been transformed by Hubble’s impact. She highlighted Hubble’s multiple science instruments and ultraviolet–optical capabilities, which cover a crucial part of the electromagnetic spectrum that is not covered by other flagship observatories like JWST. She described the evolution of Hubble, from the first description of a space telescope by Dr. Lyman Spitzer in 1946 to its announcement by Nancy Grace Roman in 1977 and eventually its launch on the space shuttle in 1990. Its key science drivers originally included measurements of the expansion rate of the universe, understanding how galaxies have evolved throughout the history of the universe, determining whether supermassive black holes really exist at the centers of massive galaxies (only a theory at the time of launch), and studying planets in our solar system. Over the past 35 years, Hubble’s ~1.7 million observations of over 100 million objects have revolutionized our understanding of the solar system, star formation, and the evolution of the universe, leading to the discovery of the accelerating expansion of the universe, confirmation of the existence of supermassive black holes, and an understanding of a dynamic and evolving solar system.

Dr. Wiseman described how Hubble is a crucial part of the suite of Great Observatories in operation today. She emphasized its importance as a follow-up telescope for transient events like supernovae, its decades-long archive for long-term monitoring of solar system planet atmospheres, and its ultraviolet coverage that complements the infrared range of JWST. She promoted new support services for Hubble data, including the Hubble Spectroscopic Legacy Archive (HSLA) — a publicly available database of archival Hubble spectra — and the upcoming Hubble Advanced Spectral Products (HASP) database, which will be public later this summer. Dr. Wiseman cited Hubble’s continually improving user support and data archives as a crucial piece of the observatory’s future while warning that continued budget cuts have impacted their ability to fund new research and threaten the facility’s ability to support new science through the end of the 2020s.

Dr. Wiseman closed with a hope that the audience would leave her talk and the AAS meeting inspired to join the celebration of Hubble’s 35 years of discoveries. She expressed excitement for the new discoveries that will be enabled by Hubble through the early 2030s and its essential part in the suite of Great Observatories over the next half decade.

Read an interview with Jennifer Wiseman here.

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Press Conference: Recent and Upcoming Discoveries in the Broader Universe (by Lucas Brown) (Briefing video)

In our final press conference of AAS 246, we heard five talks unveiling new insights into galaxies, reionization, and the universe at large. The first of these talks was given by Harrison Souchereau of Yale University, titled “Inner Tail Gas Asymmetries and Fallback in a Jellyfish Galaxy.” Jellyfish galaxies are a type of galaxy with star-forming tails of gas that trail behind the main disk. These tails are formed as a result of external pressures caused by the galaxy moving through a gas-dense medium like the space within a galaxy cluster. Souchereau’s team observed one such galaxy—NGC 4858—with the Atacama Large Millimeter Array (ALMA) radio telescope to map out not just the positions, but the velocity of gas in these tails. In doing so, they found that not only was the gas distribution asymmetric, but the gas appeared to be falling back in towards the galaxy. The team believes this shows that the gas was preferentially stripped from one side of the galaxy due to the direction of its rotation, and that the gas has since collected on the other side of the galaxy while beginning to fall back inwards. The full press release can be found here.

Next, in “In the Belly of the Beast: Massive Clump Formation in the Hearts of Major Mergers,” we heard from Sean Linden of University of Arizona about new insights from JWST into the dense star-forming clumps found in many major galaxy mergers. These clumps are unlike anything seen in typical, non-merging galaxies in the universe today, and they’re thought to be the “building blocks” of galaxies in the early universe. Thanks to the space telescope’s increased resolution and sensitivity to infrared light, it has been able to peer through the obscuring dust found within some of the universe’s biggest mergers to identify the presence and characteristics of such clumps. These new observations confirm many predictions about clump formation made in prior simulations. The full press release can be found here.

Third, we were briefed on “UNCOVERing the Drivers of Reionization with JWST” from Isak Wold of NASA and The Catholic University of America. Reionization was a period of a few hundred million years in the very early universe wherein the neutral hydrogen that permeated the cosmos at the time was nearly completely ionized. The exact origin of the necessary radiation to set off this reionization has long been a source of speculation. In Wold’s talk, new evidence was presented advancing the idea that a class of young, star-forming, and oxygen-III-emitting galaxies could completely source this ionizing ultraviolet light. Wold’s team draws on new JWST observations of such galaxies, which indicate that the galaxies are numerous, largely dust-free and metal-poor, and indeed emit abundant ultraviolet light—all the ingredients needed for a strong candidate to explain the epoch of reionization. The full press release can be found here.

Fourth, in “The ‘Dark-Matter Dominated’ Galaxy Segue 1 Modeled with a Black Hole and No Dark Halo” presented by Nathaniel Lujan of The University of Texas San Antonio, we heard about a new model for the structure of the dwarf galaxy known as Segue 1. Previous observations of the galaxy, which has few stars but a large amount of mass, suggested that the galaxy contains a large amount of dark matter. In order to derive the new model, Lujan and his collaborators compared observations of stellar motion against a set of 100,000 simulations of stellar motion given different underlying parameters describing the distribution of mass in the galaxy. The team found that a model including a central black hole with the mass of 500,000 suns and only minimal dark matter fits better than a dark matter–dominated model, challenging previous assumptions about the system, the prevalence of dark matter in dwarf galaxies, and the abundance of supermassive black holes in our universe. The full press release can be found here.

And finally, in our very last press briefing of AAS 246, we heard from Caltech’s Phillip Korngut on “First Light with the SPHEREx Observatory.” This briefing provided an update on the status of NASA’s newest space observatory, the Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx), which aims to take detailed infrared spectra of millions of galaxies and other astrophysical systems over the course of the next few years. The mission will accomplish this by scanning the entire sky with linear variable filters placed above the camera’s sensor, which essentially causes each row of each image to be sensitive to different wavelengths of light. By slowing panning over areas of the sky, this allows each pixel of an image to eventually be characterized spectroscopically. We were able to view the very first images taken by SPHEREx, as well as compilations of imagery that demonstrate the mission’s unique ability to observe objects like the nebula NGC 1760 across a wide variety of wavelengths. Data products from the mission are expected to go public in early July.

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Plenary Lecture: Advancing Exoplanet Characterization: Five Years of High-Resolution Spectroscopy with KPIC, Dimitri Mawet (California Institute of Technology) (by Margaret Verrico)

The next plenary lecture was given by Professor Dimitri Mawet, the David Morrisroe Professor of Astronomy at Caltech and a Senior Research Scientist at NASA’s Jet Propulsion Laboratory. Professor Mawet talked about the importance of ground-based observatories and high-resolution spectroscopy for exoplanet science.

Professor Mawet began with an overview of exoplanet science in the 21st century. The primary science goals in exoplanet research are understanding exoplanet demographics and diversity, learning how exoplanets form and evolve, and finding evidence of habitability and even life. More than 6,000 exoplanets have now been detected, but the vast majority have never been observed spectroscopically, which is crucial for characterizing their atmospheres, spins, orbital parameters, and weather. High-resolution spectroscopy in particular is crucial for measuring these properties, as it allows for the separation of exoplanet spectral features from the properties of the host star or Earth’s atmosphere. To that end, Professor Mawet helped develop the Keck Planet Imager and Characterizer (KPIC), a high-resolution spectrometer optimized for exoplanet science. KPIC has led to the detection of more than 30 exoplanets and brown dwarfs and several exciting discoveries.

Professor Mawet highlighted several works by his students on KPIC exoplanets. Mawet’s student Jason Wang directly imaged HR 8977, a four-planet system, and obtained spin measurements for all four planets, which can be used to study the relationship between the planets and their magnetic fields. Another one of his students, Chih-Chun (Dino) Hsu, will be giving a talk later today on the differences in the spin properties between giant planets and brown dwarfs. Using KPIC’s high-resolution spectrometer, Professor Mawet’s group has made groundbreaking discoveries in exoplanet formation science, paving the way for future work with ground-based and space-based observatories.

To wrap up the talk, Professor Mawet talked about the future of ground-based exoplanet science with the High resolution Infrared Spectrograph for Exoplanet Characterization (HISPEC) and Multi-Objective Diffraction-limited High-resolution Infrared Spectrograph (MODHIS). In particular, HISPEC is expected to nearly double the number of directly imaged planets and brown dwarfs when it comes online in 2027.

Read an interview with Dimitri Mawet here.

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Donald E. Osterbrock Book Prize Lecture: Where Are We? How Past Astronomers Found Their Place in the Universe — and on Earth, Seb Falk (University of Cambridge) (by Olivia Cooper)

In the afternoon, we heard from University of Cambridge historian Seb Falk, author of the book “The Light Ages: The Surprising Story of Medieval Science”. In his plenary (see Figure 1), Falk shared how our understanding of the Universe has evolved over the past several centuries, with a particular focus on the science of the middle ages. Before the existence of telescopes, astronomers were watching the skies and charting the motions of the stars and planets to incredible accuracy, even demonstrating that Earth is a sphere and calculating its size to within a few percent. In his book, Falk focuses on the journey of a 14th-century monk who navigated by the night sky, developed mathematical techniques to track the motions of the solar system, and kept time by the stars. Across the globe, in all regions and cultures, astronomy has been used in both tangible and esoteric ways, from ship navigation to interpretation of faith. Yet all of these pursuits are ultimately centered on understanding our position and direction as we move through the universe.

Throughout the talk, Falk shared a handful of lessons he has taken from the history of astronomy, about how to do astronomy in a changing world. First, everyone has a contribution to make: there are countless unknown, unnamed, historically-unrecognized people taking measurements, developing knowledge, and constructing instruments. Next, motivations matter, for better or worse. Our motivations for doing science (and for the way we conduct science) can provide momentum, and can also create biases and limit our scientific understanding. Further, astronomy is never pointless: though our work often seems abstract, the implications are quite grounded, and have led to the development of mathematical techniques, new technologies, art, storytelling, and more. Regarding the practice of astronomy, Falk reminds us that it is most impactful through physical experience, when we contextualize the act of doing astronomy by the experience of looking at the night sky. Upon these experiences, he notes that modeling matters; how we encode, distill, and distribute knowledge in turn impacts our collective interpretation of the cosmos.

Towards the end of the talk, Falk remarked that the pre-modern world was a time of amazing creativity, teamwork, patience, and interdisciplinarity. Although there were certainly misconceptions about the Universe and our place in it, he notes the importance of giving dead ends and disappointments a chance to pan out, and reminds us to persevere through times of political unrest and threat to scientific pursuit, as did astronomers of the past worldwide.

Read an interview with Seb Falk here.

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Plenary Lecture: Things in Disks: Towards a New Understanding of Galactic Nuclei, K.E. Saavik Ford (CUNY Borough of Manhattan Community College/American Museum of Natural History) (by Margaret Verrico)

The final plenary of the day was given by K.E. Saavik Ford, a Professor in the Science Department at CUNY Borough of Manhattan Community College, Professor of Physics at the CUNY Graduate Center, research associate at the American Museum of Natural History, and a visiting scientist at the Flatiron Institute’s Center for Computational Astrophysics. She discussed her work understanding “things in disks,” particularly stellar- and intermediate-mass black holes in active galactic nucleus disks.

Professor Ford opened with an image of the orbits of stars around the Milky Way’s central supermassive black hole, Sagittarius A*. Most of these stars are Type B, meaning there was once a population of O-type stars that have since gone supernova and left behind black holes and neutron stars. She argued that this should also be true around actively accreting supermassive black holes (active galactic nuclei, or AGN), meaning these stars and stellar remnants should be interacting with the AGN disk. These interactions will eventually have enough drag to bring those stars and their remnants into a coplanar orbit inside the AGN disk and can contribute to the formation of black hole binaries. In fact, Professor Ford argues that AGN may be a dominant formation pathway for black holes over 50 solar masses, which should not be able to form from supernovae of isolated stars. These objects have been observed as the progenitors of black hole mergers with LIGO, so their formation channels are an important piece of the gravitational wave puzzle.

Professor Ford spent most of her talk advertising McFACTS, a Monte Carlo simulation code for stellar-mass black holes embedded in AGN disks. She highlighted a few results from collaborators and students who have used the code, including her student Vera Delfavero’s modeling of the supermassive black hole mass peak at 10⁸ solar masses (ADS link here) and predictions by Harrison Cook for the gravitational wave signatures of the AGN channel (ADS link here). She also discussed ongoing and future work to improve the software’s ability to model stars, electromagnetic signatures of black hole mergers in AGN disks, and transient events like tidal disruption events, changing-look AGN, and quasi-periodic eruptions that might result from those mergers.

Professor Ford closed out the talk with several pieces of advice. She advised working with kind people and being kind in return. She reminded the audience to control what they could control and to work sustainably. She emphasized the importance of doing research, building community, having hobbies, having a plan B, and wearing sunscreen. To close out today’s series of talks, she remarked that no one knows what the future holds, whether for good or for bad.

Read an interview with Saavik Ford here.

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