Editor’s Note: This week we’re at the 242nd AAS meeting in Albuquerque, NM, and online. Along with a team of authors from Astrobites, we will be writing updates on selected events at the meeting and posting each day. Follow along here or at astrobites.com for daily summaries, or follow @astrobites on Twitter for live coverage. The usual posting schedule for AAS Nova will resume on June 12th.
Table of Contents:
- Fred Kavli Plenary Lecture: Dan Scolnic (Duke University)
- Press Conference: Discoveries in Distant Galaxies
- Oral Session: Daytime & Dark Sky Heritage in American Southwestern Archaeoastronomy
- Plenary Lecture: Edwin “Ted” Bergin (University of Michigan, Ann Arbor)
- Press Conference: Solar Swirls, Satellites, and Saving the Night Sky
- Plenary Lecture: Greg Taylor (University of New Mexico)
- Plenary Lecture: Jeyhan Kartaltepe (Rochester Institute of Technology)
Fred Kavli Plenary Lecture: Dan Scolnic (Duke University) (by Lucas Brown)
AAS started off tense this year — that is, it started with a presentation about two measurements that are in tension with each other. Professor Dan Scolnic of Duke University took the stage to give this meeting’s Fred Kavli Plenary Lecture, which focused on his work measuring the expansion of the universe with Type Ia supernovae. Over the past ten years, these sorts of “direct” measurements of the expansion rate (denoted “H0”) have honed in on a value around 73 km/s/Mpc while precise measurements of the cosmic microwave background (CMB) combined with the standard model of cosmology have suggested a value around 67.5 km/s/Mpc. What gives?
The first portion of Prof. Scolnic’s talk helped bring us up to speed on the history of the Hubble constant and the idea of the expanding universe itself. More than 100 years ago, Einstein completed his general theory of relativity, and he set out to apply his new theory to the universe as a whole to understand its cosmological implications. Quickly, he found that in order to have a static, eternal universe, a constant term had to be added to his field equations — the “cosmological constant.” Einstein insisted for much of his life that any non-static models of the universe derived from his theory had to be wrong in some way, Prof. Scolnic noted, but the idea of a dynamic universe was eventually vindicated through observations. Those observations, carried out initially by Harvard astronomer Henrietta Leavitt and then expanded upon by Edwin Hubble, involved measuring the distances to far away galaxies using Cepheid variable stars, whose intrinsic brightness can be deduced from their period of brightening and dimming. By tracking the relation between the distance to a galaxy and the velocity at which it recedes from us, Hubble and his successors demonstrated the expansion of the universe.

This plot demonstrates the distance ladder technique used by cosmologists to measure the scale of the universe as well as cosmological parameters like the rate at which the universe is expanding. Local measurements using stellar parallax are used to calibrate distance estimates for Cepheid variable stars, which are then used to calibrate distance estimates for Type Ia supernovae. Click to enlarge. [Reiss et. al. 2021]
This discrepancy, known as the “Hubble tension,” has led to large amount of criticism being levied at the work of Prof. Scolnic and his collaborators, as some believe the tension is most easily explained as being the result of systematic errors in their analysis. However, Prof. Scolnic and his teams have worked diligently over the past several years to address these concerns. In his presentation, Prof. Scolnic demonstrated how even tweaking over a dozen aspects of their analysis couldn’t get H0 below about 72.5 km/s/Mpc, still far from the 67.5 km/s/Mpc derived from CMB measurements. Removing entire “rungs” on the cosmic distance ladder also fails to resolve the tension. Prof. Scolnic believes that their measurements are indeed correct, and that part of why other physicists are so apprehensive about the analysis is that there isn’t anything immediately obvious on the theoretical side that can fix the tension. In many theoretical explanations, a radical change in the dynamics of the universe must occur at either very early or very recent times. Prof. Scolnic largely dismisses the latter conclusion, highlighting a paper that speculates on the possibility that a rapid change in the gravitational force ~100 million years ago may have occurred, coinciding with the extinction of the dinosaurs. The bizarre connection here is meant to demonstrate how sparse the evidence is for these recent-universe changes. On the other hand, Prof. Scolnic thinks some theories which modify early-universe dynamics may be promising, such as “early dark energy.” Regardless of what exactly turns out to resolve the Hubble tension, there is clearly a lot left to learn about the history of our universe.
Press Conference: Discoveries in Distant Galaxies (by Sumeet Kulkarni)
The press office at AAS 242 decided to begin their press conference schedule from a long, long time ago and in galaxies far away, with subsequent press conferences bringing us gradually closer to home by Wednesday. This first one, though, was all about discoveries in distant galaxies using new-age probes that extend humanity’s sense-making capabilities almost beyond comprehension — through gravitational wave detectors such as LIGO and Virgo and telescopes like JWST.

Artist’s impression of a cocoon debris emitted from supernovae that could generate gravitational waves. [Ore Gottlieb/CIERA/Northwestern University]
Next up was a trio of presenters unveiling new results from the JWST-JADES project. JADES, short for the JWST Advanced Deep Extragalactic Survey, is a massive hunt for galaxies especially from the early universe (when it was only around 600 million years old). In late 2022, the team broke the record for the earliest discovered galaxy, and they expect to keep breaking milestones as new data rolls in.
The first speaker, Marcia Rieke from Arizona State University introduced the JADES project and its latest data release. This was followed by Kevin Hainline from the Steward Observatory who gave an outline of exactly how early of an universe their team is probing. JADES’ dataset of galaxies from less than 600 million years since the Big Bang now numbers at 717, up from only a dozen or so before JWST! “It’s exciting that we can even talk about these (early) times,” Hainline said. More than 93% of these galaxies, which formed the early hydrogen and helium crucial for the evolution of our universe, were never seen before JWST. But now, not only can we detect these infant galaxies, but we can also see complex structures in them, including one dumbbell-shaped early galaxy which is Hainline’s favorite. [Press release]
Ryan Endsley from UT Austin gave the next JWST update about dwarf galaxies. He said that ultraviolet emission lines from the recombination of hydrogen ions are valuable probes of star formation in early galaxies. In particular, they are great probes to study dwarf galaxies, given JWST’s ability to detect emission lines from galaxies that are 50 times fainter than what was possible before. It is now also possible to compare whether bright and faint galaxies from the early universe developed differently. And indeed, the JADES team found that the brightest galaxies underwent more star-formation bursts — events wherein matter equivalent to several tens of Suns formed at once. [Press release]

JWST image of the Einstein ring of a lensed galaxy 12 billion light-years away (in red) surrounding a foreground galaxy (in blue) 3 billion light-years away. Click to enlarge. [Slide by Jane Rigby]
The final press briefing of this morning was given by Patrick Kamieneski from Arizona State University, who talked about a dusty and warped Milky Way-like galaxy nicknamed “El Anzuelo.” Spanish for a fish-hook, this term aptly describes the shape of this galaxy which is 11 billion light-years away. While similar in size and a dustier version of our own galaxy, El Anzuelo forms stars at more than 80 times faster than the Milky Way. JWST’s incredible infrared detection capabilities have made it possible to dramatically improve the way in which we can study such objects, as emphasized by the image below.
Return to Table of Contents.Oral Session: Daytime & Dark Sky Heritage in American Southwestern Archaeoastronomy (by Emma Clarke)

Example of a gnomon — a vertical construction that casts a shadow. Pebbles mark the shadow’s trajectory over time as the Sun makes its daily path across the sky. [From slide by Tony Hull]
Next up, Cherilynn Morrow discussed the outreach program associated with NASA’s PUNCH mission: four “suitcase-sized” spacecraft focused on the inner heliosphere between the Sun and Earth that is scheduled to launch in 2025. The PUNCH outreach program focuses on the sun as a natural extension of the human understanding of the sun and its rhythms. The program shares the interconnections between historical sun watching, such as interpreting the “eclipse” petroglyph site at Chaco Canyon, and modern Sun-watching, both by NASA missions and all contemporary people observing sunrise, sunset, light and shadow cast by the Sun, and eclipses.

The “eclipse” petroglyph in Chaco carved by the Ancestral Puebloan people may have been inspired by the total solar eclipse in 1097. [From slide by Cherilynn Morrow]
Closing the session, Michael Rymer spoke briefly about archaeoastronomy and international dark sky places. The International Dark-Sky Association’s International Dark Sky Places Program encourages areas around the world to preserve dark sites through policies and public education. Two dark sky places in the US — Chaco Culture and National Historic Park in New Mexico, and Hovenweep, on the border of Utah and Colorado — are also archaeoastronomical sites. Protection of the dark night sky at these places not only makes better stargazing, but is also important for preservation of wildlife and plants. There is a growing list of potential future sites of dark-sky parks in the US.
Plenary Lecture: Edwin “Ted” Bergin (University of Michigan, Ann Arbor) (by Junellie Gonzalez Quiles)
Murthy Gudipati from the Jet Propulsion Laboratory (JPL) introduced the Laboratory Astrophysics Division and invited everyone to become familiar with the division and join as members. He then introduced the plenary speaker, Prof. Edwin “Ted” Burgin from the University of Michigan, Ann Arbor. His talk titled “The Birth of Planets and the Story of Carbon” started with his recognition of laboratory astrophysicists and their role in helping understand the fundamentals needed to study astrophysical phenomena. Ted then transitioned to mentioning how the search for life has driven the connection between chemistry in protoplanetary disks to the atmospheric composition of exoplanets. This link is essential if we want to fully understand how planetary systems are formed and, therefore, how individual exoplanets are formed.

Shown here is the bulk carbon to silicon ratios for the Earth and solar system bodies. Click to enlarge. [Slide by Ted Bergin, from Bergin et al. 2015]

Here you can see the TW Hya system and their C2H detection from the Bergin et al. 2016 paper. Click to enlarge.
During his plenary, he also spoke about isotopic fractionation and how it offers a new window into planet formation. He showed the TW Hya system, where they looked at the ratio of 12C to 13C. This can be done for other planetary systems to say whether the system could be carbon rich (see Figure 1). He then ended his talk by talking about our own planet. Earth is relatively carbon poor compared to our Sun, Venus, and other types of chondrites (see Figure 2). Earth was formed of mainly refractory materials with small amounts of soot and water, and he aims to understand soot in the context of exoplanets. He also studied the geological processes that could lead to outgassing on exoplanets and how the carbon inventory can lead to methane in their atmospheres and potentially hazes as well.
He is very interested in how all of these aspects of planetary formation and evolution could impact the habitability of exoplanets, and it is certainly something to look out for in our search for life in other worlds!
Press Conference: Solar Swirls, Satellites, and Saving the Night Sky (by Lucas Brown)
The second press conference of the day switched gears from the distant reaches of the universe to our local corner of space, with presentations on a new solar weather phenomenon, the positives and negatives of artificial satellites for astronomy, and updates on efforts to preserve the night sky.
First up was Oana Vesa from New Mexico State University, who spoke on new research into solar tornadoes. That’s right — there are tornadoes on the Sun. Only discovered in 2008, there is little known about the formation mechanisms behind these tornadoes or their overall role in the solar environment. Vesa explained that these tornadoes, consisting of hot, swirling plasma, are bound to the surface of the Sun magnetically, and can channel mass and energy up through different levels of the solar atmosphere. And like most things on the sun, their scale is massive. These chaotic solar vortexes vary from the size of a city all the way up to the size of Earth. Through new observations performed at the Dunn Solar Telescope, Vesa’s team has tracked dozens of these events, and they have begun the process of cataloging and analyzing their behaviors. So far, the team has found the tornadoes to have an average lifespan of about 8 minutes, and some have been seen to form in pairs or exhibit chaotic spiraling patterns. There’s a lot left to learn about these fiery storms. [Press release]

An image of the main science component of ORCASat, containing a laser module, photodiodes, and an integrating sphere, also known as a Lambertian sphere. ORCASat is designed to help calibrate ground-based telescopes. Click to enlarge. [ORCASat/University of Victoria Centre for Aerospace Research]

Plots showing how the Median Radon Transform algorithm can identify satellite trails in imagery from the Hubble Space Telescope (HST). The top plot is a HST image containing a satellite trail, while the bottom right image is produced by applying a Median Radon Transform. The satellite trail now appears more similar to a point source. [Figure 3 in Stark et. al. 2022]
Closing out today’s second press conference, James Lowenthal from Smith College spoke about efforts to protect the night sky from light pollution. He noted that terrestrial light pollution from cities is in many ways a more significant threat to astronomy than satellite trails, and has many other negative effects such as harming plants and animals which are all used to a particular day-night cycle that has been disrupted in recent years. He also highlighted the spiritual significance of the night sky to many native communities. Lowenthal noted that dark sky advocacy groups have grown in recent years thanks in part to renewed interest due to the growth of satellite mega-constellations like SpaceX’s Starlink. Through the efforts of dark sky groups and their partnerships with native communities, local governments, and industry, some strides have been made towards preserving the night sky, such as creating new lighting standards centered around preserving the night sky while still illuminating cities. However, much more work has to be done given that recent research has shown that light pollution is increasing at much higher rates than previously thought due in part to the proliferation of LEDs. One of the success stories Lowenthal highlighted in his talk was the protections enacted in Coconino County, Arizona, home to numerous historic observatories. Another recent example given was the enacting of official dark sky protections in central Maine, one of the last remaining dark sky sites east of the Mississippi River. [Press release]
Plenary Lecture: Greg Taylor (University of New Mexico) (by Ben Cassese)
Greg Taylor of the University of New Mexico delivered the third plenary of the day. Over the course of 45 minutes, Prof. Taylor took the denizens of Ballroom C and the Zoomiverse on a whirlwind tour of science conducted with the Long Wavelength Array (LWA) over the past decade. This instrument, a collection of 256 individual antennae spread throughout a 100-meter ellipse, has touched an impressive number of subfields in that time: From pulsars to the solar wind, the LWA has seen (and measured) it all.

A schematic of how the LWA detects an incoming meteor. [Prof. Greg Taylor, University of New Mexico]
Taylor also shared an overview of observations designed to test models of the solar wind. Here, the LWA stared at a pulsar (during the day! Radio astronomy is great like that) and measured how its signal changed as the Sun edged closer and closer to their line of sight. This let the team probe different regions of interplanetary space and constrain the ionized material that hovers within the solar system and slightly distorts radio signals.

Plans for the “swarm” of detectors to complement/supplement the LWA. Click to enlarge. [Prof. Greg Taylor, University of New Mexico]
Plenary Lecture: Jeyhan Kartaltepe (Rochester Institute of Technology) (by Sumeet Kulkarni)
“Far and wide eyes of the JWST” was the theme of the final plenary session at AAS 242 on Monday. Prof. Jeyhan Kartaltepe from the Rochester Institute of Technology talked about results from two wide-ranging projects from the first JWST observing cycle and how they are constantly molding our knowledge of cosmic history.
Kartaltepe began with a brief overview of JWST’s capabilities and how its infrared eyes unlock the deepest reaches of the universe by detecting light that has been redshifted to those wavelengths due to cosmic expansion. JWST was always going to be pathbreaking, and all astronomers knew it. When asked how many in the plenary woke up early (in US time zones) to watch it launch on Christmas day in 2021, 90% of the hall raised its hands.

The reach of different deep field images towards the early universe in terms of redshift. [Prof. Guinevere Kauffmann, MPA Garching]
But among the exciting early galaxy candidates also hide several mimickers: nearby, dusty galaxies also have the same red, blobby appearance which can be mistaken to be one due to high redshift by photometry (studying properties of the images) alone. But JWST does much more than just click pictures of these galaxies. It can also study their character using a spectroscope, or a prism that splits light to unveil the telltale signatures of molecules within it. The spectroscopic data from JWST of Maisie’s galaxy was so clean, that it “looked just like that of a nearby galaxy,” said Kartaltepe. This helped them confirm its age of being only around 390 million years after the Big Bang! Spectroscopy also helps confirm (or reevaluate) the age of early galaxy candidates. Kartaltepe gave an example of a galaxy first believed to have a redshift of 16 (placing it among the earliest ever detected galaxies), which was then reduced to 4.9 thanks to the JWST’s NIRSpec data.
The second project that Kartaltepe is excited about is Cosmos-Web. This project covers a relatively big patch of the sky, just larger than the full Moon, but goes deep into it with JWST’s far-reaching eye to record all galaxies near and far that lie within. This patch of the sky was chosen because part of it has been extensively studied by the Hubble space telescope, allowing for extracting science out of the two sets of observations in tandem. As of today, Cosmos-Web has completed about half of its observations and is already finding large numbers of high-redshift galaxy candidates, dusty star-forming galaxies, and more!Kartaltepe concluded her plenary by stressing the importance of mentorship in furthering our field and supporting the progress of students and early career researchers. “I wouldn’t be here if not for excellent mentors,” she said, and urged all students today to pick an advisor who prioritizes seeing them as a person first.