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:
- Fred Kavli Plenary Lecture: Unveiling the First 500 Myr of the Universe with CEERS, Steven Finkelstein (University of Texas, Austin)
- Press Conference: Cosmic Accelerators and Active Black Holes
- Helen B. Warner Prize Lecture: Magnetism and Morphology: Decoding the Interstellar Medium, Susan Clark (Stanford University)
- Press Conference: From Molecules to Molecular Clouds: Discoveries in the Milky Way
- George Ellery Hale Prize Lecture: Why are the Coronae of the Sun and Other Stars so Darned Hot?, James Klimchuk (NASA GSFC)
- Plenary Lecture: Supernovae: The Ultimate Laboratories of Extreme Astrophysics, Danny “Dan” Milisavljevic (Purdue University)
Fred Kavli Plenary Lecture: Unveiling the First 500 Myr of the Universe with CEERS, Steven Finkelstein (University of Texas, Austin) (by Olivia Cooper)
Kicking off Day 1 of AAS 246, Professor Steve Finkelstein (UT Austin) gave his prize plenary titled “Unveiling the First 500 Myr of the Universe with CEERS.” In it, he shared the stories and surprises of CEERS (Cosmic Evolution Early Release Science Survey), one of the earliest programs with JWST, comprised of an international team of extragalactic astronomers led by Prof. Finkelstein. Though he admittedly “suffered from a lack of imagination” at first and supposed the survey would merely confirm past assumptions about galaxy evolution, instead CEERS has uncovered new mysteries about galaxies in the very early universe.
Prof. Finkelstein’s main scientific goal is to find out when the lights first turned on, or when galaxies formed out of the cosmic dark ages. To understand this beginning of everything, Finkelstein and his team work to observe galaxies at earlier and earlier times, count them up, and investigate what they look like. With the longer wavelength coverage and sensitivity of JWST, we can push this galaxy counting technique to even earlier times, within the first few 100 million years (of about 14 billion years from the Big Bang to now). Even in the first few days after receiving the first data from CEERS (see Figure 1), the team found a few surprises, all of which have since held up: the early universe is full of (1) too many unexpectedly bright galaxies, (2) galaxies that are too massive, and (3) lots of accreting supermassive black holes. With more detailed data coming in from spectroscopic follow-up programs, the team is now working towards confirming these galaxy puzzles, and eventually determining the physical origins of the seemingly rapidly evolving early universe.
A few team members looking at some of the first data from CEERS at the TACC visualization lab at UT Austin. The image is full of galaxies, and is displayed over multiple screens spanning the room, with the scientists’ silhouettes appearing over the image. [R. Larson]
Press Conference: Cosmic Accelerators and Active Black Holes (by Lucas Brown) (Briefing video)
This press conference session marked the very first of the meeting, and featured five presentations covering various exciting developments in the study of our universe’s biggest and brightest natural particle accelerators.
The first of these presentations, “Multimessenger Probes of Galactic PeVatrons,” was given by Shuo Zhang from Michigan State University. PeVatrons are, broadly speaking, any astrophysical source that is able to accelerate particles to PeV-scale energies. These are thought to include pulsar wind nebulae, supernova remnants, molecular cloud interactions, star-forming regions, and various black hole systems. Zhang shared that her team recently identified a pulsar wind nebula candidate that was spatially associated with an energetic cosmic-ray event detected by the Large High Altitude Air Shower Observatory (LHASSO) known as J0343+5254u. They believe this system could be the source of this particular high-energy event. Additionally, Zhang shared that her team has launched new searches for PeVatron star-forming regions using the IceCube neutrino detector. The full press release can be found here.
A composite image of the galaxy cluster PLCK G287.0+32.9 shown in radio and X-ray emission is displayed. The X-ray signal shines strongest in a central spherical region, while the radio is offset and in the form of two large arcs. [X-ray: NASA/CXC/CfA/K. Rajpurohit et al.; Optical: PanSTARRS; Radio: SARAO/MeerKAT; Image processing: NASA/CXC/SAO/N. Wolk]
Third, in “Chandra Reveals Two Distant Quasars Transforming Universe’s First Light into High-Energy X-Ray Jets,” Jaya Maithil from the Center for Astrophysics | Harvard & Smithsonian talked about quasars, which are the brightest objects in the entire universe. She shared that her team identified two quasars in the early universe (with the light from them originating only 3 billion years after the Big Bang). Quasars from this era are important to understand because this cosmic epoch is when star formation and quasar activity is thought to have peaked. These quasars were detectable thanks to the exceptional power of the Chandra X-ray Observatory and the quasars’ ability to boost cosmic microwave background photons to X-ray energies due to their strong jets. In one of the quasars, the team found that the jet contributed a whopping half of the quasar’s entire energy output, the equivalent of 10 trillion suns! This discovery will hopefully shed light (literally) on the role of quasars in shaping galactic environments in the early universe. The full press release can be found here.
Finally, in “Multi-Phase Shocks and Feedback in a Nearby Spiral Galaxy Revealed by JWST Imaging,” Travis Fischer from the Space Telescope Science Institute informed us on JWST’s new insights into the role of shocks and active galactic nucleus feedback within galaxies. This work focused specifically on a nearby galaxy NGC 4258. While radio emission features in this galaxy have long been assumed to result from active galactic nucleus jets, JWST’s high-resolution observations of substructure in the galaxy for various different materials like iron or dust grains makes the jet-origin scenario less likely. Instead, Fischer’s team believes that a slower-moving active galactic nucleus wind provides a better explanation for the distribution of materials along the regions where radio emission is observed, supporting the idea that extended radio features in galaxies may not always be the result of jets as previously assumed.
This collage features three views of Messier 106, also known as NGC 4258. The first two images show the target in visible light as seen by Kitt Peak National Observatory and the Hubble Space Telescope. The image on the right is from JWST in the infrared. [ESA/Webb, NASA & CSA, J. Glenn, KPNO/NOIRLab/NSF/AURA, the Hubble Heritage Team (STScI/AURA), R. Gendler, M.T. Patterso, T.A. Rector, D. de Martin & M. Zamani; CC BY 4.0]
Helen B. Warner Prize Lecture: Magnetism and Morphology: Decoding the Interstellar Medium, Susan Clark (Stanford University) (by Karthik Yadavalli)
This session, chaired by Grant Tremblay, was the lecture given by Dr. Susan Clark after receiving the Helen B. Warner Prize Lecture. Dr. Clark gave a detailed overview of the interstellar medium (ISM) and how the galactic magnetic field permeates through it. She detailed how the magnetic field can be probed through Faraday rotation, synchrotron radiation polarization of starlight, and polarization of dust emission. One of the key findings presented by Dr. Clark is that the distribution of the magnetic field in the ISM is correlated with the distribution of neutral hydrogen in the ISM. It turns out that even though the neutral hydrogen component isn’t charged, a very small fraction (~10-4) of that hydrogen is actually ionized, allowing the magnetic field to couple to the gas. Therefore, Dr. Clark and her group are able to learn about dust polarization from observations of the neutral hydrogen density and velocity fields.
The velocity field of neutral hydrogen overlaid with the direction of the magnetic field. Color gives the observed line-of-sight velocity and the contours give the direction of the magnetic field. The two are correlated over this patch of the sky. [Adapted from Ade et al. 2023]
A decomposition of the interstellar material into a cold component (top), warm component (middle), and residual noise (bottom) using an autoencoder. [Adapted from Lei et al. 2025]
Press Conference: From Molecules to Molecular Clouds: Discoveries in the Milky Way (by Olivia Cooper) (Briefing video)
This press conference covered recent findings within our home Milky Way galaxy, from the detection of complex dust molecules, to the emergence of elusive stellar activity, to advances in techniques for mapping the galaxy’s gaseous disk.
Artist’s rendition of the cyanocoronene molecule, which has seven interconnected benzene rings and a cyano group. [NSF/AUI/NSF NRAO/P.Vosteen; CC BY 4.0]
Next, in “Discovery of the Elusive Radio Burst Indicators of Massive Eruptions in a Young Active Star,” Atul Mohan (NASA-GSFC/The Catholic University of America) presented the first detection of coronal mass ejection–associated radio bursts in an active star. He noted that though these bursts of radio emission are expected alongside these energetic stellar eruptions, they have not yet been detected in a decades-long search until now, primarily due to line-of-sight effects given that the radio emission is localized.
In “The Spotty Surface of the Blue Giant Xi Persei,” Tahina Ramiaramanantsoa (Arizona State University) showed the second case of bright spots discovered on a massive star. These spots are unexpected for massive stars as they have fundamentally different structures than the Sun, where such spots are typically seen. Through time–frequency analysis of 13 years of space-based observations from small and large satellites, the team found that the spots come and go, but their origin remains unknown.
Peter Craig (Michigan State University) took us from individual molecules and stars to the larger structure of the Milky Way in “A Map of the Outer Gas Disk of the Galaxy with Direct Distances from Young Stars.” Given our viewpoint from within the galaxy, it is challenging to construct a complete map of the gaseous disk of the Milky Way, which we know must have a complex structure. In the past, astronomers have used the motions of the gas relative to our position to infer the structure from a top-down view. However, it is prohibitively challenging to measure the distance to each parcel of gas, meaning these conversions can suffer from inaccuracies. In their recent work, Craig and team demonstrated a new technique to map the disk more accurately and completely: first, they measure the motion of the gas, then, assuming young stars remain near their natal gaseous clouds, measure distances to the stars to estimate the distance to the gas. This has resulted in more accurate maps, which reveal fluffy spiral structures in the galaxy’s gas disk. See the full press release here.
Infrared images of the galactic center, showing gas and dust clouds illuminated in red and blue with a few bright red or blue stars embedded in the clouds. Two star forming regions that were studied are shown as zoomed-in insets, where hot, blue massive stars are seen causing the gas clouds to glow. [J. De Buizer (SETI) / SOFIA / Spitzer / Herschel]
George Ellery Hale Prize Lecture: Why are the Coronae of the Sun and Other Stars so Darned Hot?, James Klimchuk (NASA GSFC) (by Karthik Yadavalli)
This session, chaired by Dawn Gelino, was the lecture given by Dr. James Klimchuk after receiving the George Ellery Hale Prize Lecture. In this talk, Dr. Klimchuk specifically wanted to present about three different studies he did recently, each on three different approaches: observational, theoretical, computational. The guiding question about his research is why the Sun’s corona is so hot. Dr. Klimchuk presented what must be the story of how the corona is structured and heated in this way. Magnetic field lines travel through the solar photosphere, loop through the corona, and loop back into the photosphere. Dynamics of the plasma in the photosphere move around the “foot points” of the magnetic field lines, causing the field lines to get twisted with each other. This twisting causes the field lines to suddenly “snap,” releasing a burst of energy. This energy is thought to heat the corona.
Left: A representative ultraviolet image of the Sun, showing the magnetic field loops in the corona. Right: A zoom in on one active region where a lot of energy can be emitted into the corona. [Slide by James Klimchuk]
Left: A schematic of the simulation, showing the field tube. Right: The flux emitted along one cross section of the field tube as it “snaps.” This flux heats the solar corona. [Slide by James Klimchuk]
Plenary Lecture: Supernovae: The Ultimate Laboratories of Extreme Astrophysics, Danny “Dan” Milisavljevic (Purdue University) (by Lucas Brown)
JWST NIRCam image of the supernova remnant Cassiopeia A. [NASA, ESA, CSA, STScI, Danny Milisavljevic (Purdue University), Ilse De Looze (UGhent), Tea Temim (Princeton University)]
Dan Milisavljevic speaks at AAS 246. [Lucas Brown]