Editor’s Note: This article was co-written by Lucas Brown and Alexia Kubas, our 2026–2027 AAS Media Fellows. We’re excited to welcome Lucas and Alexia to the team and look forward to featuring their writing on AAS Nova regularly!

Planetary nebulae mark a key evolutionary phase for low- and intermediate-mass stars, but properties of the parent star are difficult to sleuth out. Researchers have discovered an extragalactic planetary nebula in the center of a star cluster, offering an unprecedented opportunity to trace planetary nebula properties to parent star stats.

The Puzzle of Planetary Nebula Progenitors

A planetary nebula, so named because the first ones discovered resemble the planet Uranus in a small telescope, forms when a Sun-like star runs out of fuel and sheds its outer layers, leaving a hot remnant core enveloped in a gaseous nebula. At higher masses, a different process kicks in: stellar cores can collapse to produce a chaotic burst of stellar material called a supernova. Where exactly the boundary should be placed between planetary nebula progenitors and supernova-forming stars remains an outstanding question in the field of stellar evolution.

Answering this question is challenging because once a planetary nebula becomes visible, the progenitor star’s transition into a hot, compact white dwarf is already underway, making it difficult to determine the star’s initial mass. For this task, researchers seek out planetary nebulae within open clusters — groups of stars that were born from the same molecular cloud and are roughly the same age — so that cluster characteristics can help piece together the progenitor puzzle. Since open clusters tend to be relatively young, they are also a great tool to probe planetary nebulae from more massive progenitors and explore the boundary between stars that produce planetary nebulae and those that go supernova.

Striking Gold

Open cluster AP 210 and planetary nebula M279 in the Andromeda Galaxy, as seen in archival Hubble observations. Click to enlarge. [Chen et al. 2026]

To make this identification, Chen’s team used archival Hubble Space Telescope and MMT data to examine the location of the planetary nebula candidate M279 within the Andromeda Galaxy. The researchers’ critical observation was that the nebula not only overlaps with the position of an open star cluster called AP 210, but it also has an estimated velocity that matches the velocity of other stars in the cluster. These associations, when combined, provide strong evidence that M279 originated within the cluster.

Color–magnitude diagram of stars in the open cluster AP 210. Colored dots represent stars, and the red line is the best-fitting isochrone, which was used to determine the cluster’s age. Click to enlarge. [Chen et al. 2026]

What’s My (Cluster) Age Again?

M279’s cluster origin has significant consequences for pinning down the properties of the progenitor star. First, stars in open clusters all form at roughly the same time — 90 million years ago in the case of AP 210 — allowing the authors to set a tight constraint on the progenitor’s age. Then, because the rate at which a star burns through its nuclear fuel and generates a planetary nebula is related to its initial mass, the researchers are able to connect this age to a specific progenitor mass of around 5.7 solar masses.

The team also subtracted the central star’s contribution from the observed spectrum to isolate the nebula’s composition, illuminating specific nuclear processes relevant to higher-mass stars. Planetary nebulae are cosmic cocktails whose chemical abundances trace the composition of the interstellar medium when the progenitor formed as well as elements formed via nucleosynthesis inside the star during its lifetime. Chen and collaborators found the nebula to be significantly nitrogen-enhanced, which is consistent with a massive asymptotic giant branch progenitor undergoing hot bottom burning that converts carbon to nitrogen. This newly minted metal would then be mixed back into the star’s outer layers, flooding the resultant nebula with its particular spectral signature.

While this work represents only a single observation of a high-progenitor-mass planetary nebula — and only the third compelling extragalactic planetary nebula–open cluster pair — it opens up the possibility that there may be many more waiting to be found, unlocking new insight into the lives of massive stars.

Citation

“A Planetary Nebula from a 5.7 M_⊙ Progenitor in a 90 Myr M31 Star Cluster,” Pinjian Chen et al 2026 ApJL 1005 L2. doi:10.3847/2041-8213/ae77e4

The post Extragalactic Planetary Nebula with Massive Progenitor Sheds Light on Stellar Evolution appeared first on AAS Nova.

Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

Title: The Exozodi Spectral Effect: Residual Habitable Zone Dust May Bias exoEarth Characterization
Authors: Miles H. Currie et al.
First Author’s Institution: NASA Goddard Space Flight Center
Status: Published in AJ

Figure 1: Zodiacal light as seen from Cerro Paranal. [ESO/Y. Beletsky; CC BY 4.0]

This zodiacal dust is not exclusive to the solar system. Other star systems, such as Tau Ceti and Vega, have been found to host similar clouds of interplanetary dust. This means planets imaged in these systems will also have emission from this dust mixed into the light that we observe from the planets. The Habitable Worlds Observatory (HWO) is a future space telescope mission under development by NASA. One of its primary science goals is to directly image 25 Earth-like planets in the habitable zones of nearby stars and look for signs of life (or biosignatures) in these planets’ atmospheres. Exozodiacal dust (aka exozodi) represents the biggest source of astrophysical noise that will need to be subtracted out from HWO observations of exoEarths. The authors of today’s article look at the potential impact of exozodi emission on the spectra of exoEarth atmospheres.

Figure 2: Different models of three “zodis” of dust observed at an inclination of 60 degrees plotted across HWO’s potential wavelength range. The gray scattering model is shown in green, the solar system’s model is shown in black, with the red and blue debris disk models shown in their respective colors. The top panel shows the flux contrast between the dust and the star. The middle panel shows the flux per area. The bottom panel shows the total flux captured with a 7.2-meter HWO with the thin blue line representing the spectrum of an Earth twin 10 parsecs (33 light-years) away for comparison. [Currie et al. 2026]

Show Me the Zodi

The authors first assume four different models of exozodi dust and how the dust’s emission changes with wavelength. The first model assumes a dust cloud that acts as a gray scatterer, meaning the particles scatter all wavelengths of light with no preference, and the second model’s dust acts just like the solar system’s does. However, it’s unknown whether the composition of exozodi will be the same as the solar system’s. Therefore, they adopt two more models of exozodi that act just like debris disks that have different compositions. One model is bluer in color because it is made up of smaller particles that preferentially scatter blue light, and the other model is redder in color because it is made up of bigger dust particles or different chemical compositions. Each of these models over HWO’s wavelength range can be seen in Figure 2. The authors then simulate a modern Earth atmosphere (both clear and 50% cloudy) as well as an Archean Earth atmosphere to understand how different exozodi models will affect observations of different exoplanet atmosphere conditions and compositions.

There’s Dust in My Spectra

In general, the effect that zodiacal dust has on the spectra of Earth-like planets can be broken down into two categories: its effect on the continuum and on the spectral features. The continuum is the object’s light emitted over all wavelengths and uninterrupted by spectral features. Spectral features are absorption and emission lines. These create either a dip or peak in the spectrum where atoms have either absorbed or emitted light at that particular wavelength. Lines at specific wavelengths tell us that a certain material is there, providing a list of possible chemicals that could be present in the planet’s atmosphere. For a brief summary of spectroscopy more generally, see here.

In the case of the continuum, exozodiacal emission raises the continuum, meaning the base flux of the planet is raised and absorption lines become more shallow. These effects can be seen in Figure 3, where the authors’ simulated spectra are plotted with and without zodiacal dust included. Not only is the continuum elevated for all models including zodiacal dust, notice how the dips become shallower at longer wavelengths. Because dust primarily radiates thermally, the red debris disk model nearly smooths out all dips beyond 1.25 microns! Molecules that absorb at these longer wavelengths, such as water or methane, may not be correctly identified with this type of exozodiacal emission.

Figure 3: Spectra of simulated modern-Earth atmospheres for clear (solid bright lines) and cloudy (solid dimmer lines) scenarios. The Archean Earth atmosphere is plotted in dotted gray. The redder exozodiacal spectrum has an elevated continuum and smoothed spectral features as opposed to the original, zodi-free spectrum plotted in black. [Currie et al. 2026, with annotations by Kaz Gary]

From Figure 3, the effects of zodiacal dust are minimized with a bluer zodiacal dust model. This means systems with “bluer” zodiacal dust may be more optimal for HWO observations, as bluer dust does not scatter as much starlight as gray, solar system–like, or red dust. From their results, the authors recommend that the residual exozodi-to-planet flux ratio (in the V-band wavelengths) be kept to less than 10^-2 in order to correctly understand the line depths (identify if a molecule is present or not) and 10^-3 in order to accurately retrieve molecular abundances (understand how much of a molecule is present in the atmosphere). Dust is pesky enough here on Earth, but to find life on another planet like ours, we’ll dust have to deal with it.

Original astrobite edited by Anavi Uppal.

About the author, Kaz Gary:

I am a fourth-year PhD candidate at The Ohio State University with a passion for planets. My current work focuses on modeling exoplanet observations for the Habitable Worlds Observatory and understanding planetary atmospheres. Outside of research, I help develop planetarium shows and love all forms of science communication. In my free time, I enjoy playing tabletop RPGs, painting, watching terrible reality TV, and hanging out with my pet hedgehog.

The post Dust Deal with It appeared first on AAS Nova.

In 2017, we announced a new AAS-sponsored program for graduate students: the AAS Media Fellowship. This quarter-time opportunity is intended for current graduate students in the astronomical sciences who wish to cultivate their science-communication skills. This year, for the first time, we are welcoming two Media Fellows to the team.

We are pleased to announce that Lucas Brown and Alexia Kubas have been selected as our AAS Media Fellows for 2026–2027.

Alexia Kubas, a 2026–2027 AAS Media Fellow, is a graduate student at Cornell University.

Alexia majored in astronomy with minors in physics, math, and planetary sciences at the University of Arizona. They are now a fifth-year PhD candidate at Cornell University, researching periglacial processes on Earth and Ceres. Outside of research, Alexia founded and currently helps run an Ithaca, NY, chapter of Astronomy on Tap.

Lucas majored in physics with an astronomy concentration at the University of California, Davis, and he has a master’s degree in physics from Tufts University. He is now a physics PhD candidate at the University of California, Santa Cruz, where he works with Stefano Profumo on studying the phenomenology of primordial black holes. Outside of research, Lucas participates in outreach activities through organizations like the Santa Cruz Organization for Outreach in Physics and the Project for Inmate Education. He also serves as co-chair of the Astrobites collaboration.

2026–2027 AAS Media Fellow Lucas Brown is a graduate student at the University of California, Santa Cruz.

As AAS Media Fellows, Alexia and Lucas will regularly write and publish summaries of the latest astronomy research on AAS Nova, assist in managing the distribution of press releases as part of the AAS press office, and gain a broad understanding of the worlds of scientific publishing, communications, and policy. Alexia and Lucas will also be assisting with the press conferences at the upcoming AAS meetings, so please say hello if you spot them at future meetings!

As we welcome our new Fellows to the team, we’ll also soon bid farewell to Lexi Gault, our 2024–2026 AAS Media Fellow. Lexi will be continuing her PhD research at Indiana University, where she studies the interstellar medium conditions in nearby low-mass galaxies. After defending her PhD in Spring 2027, Lexi plans to pursue a postdoc in extragalactic astronomy or a full-time science writing position.

Please join us in welcoming Lucas and Alexia as our new Media Fellows and wishing Lexi the best in all her future endeavors!

The post Welcome and Farewell to Our AAS Media Fellows appeared first on AAS Nova.

For decades, astronomers have tried to decipher the source of carbon oxides on Uranus’s largest moons from ground-based telescopes. A recent study has leveraged JWST spectroscopy and laboratory experiments to identify carbon oxides and their origins for Ariel, Umbriel, Titania, and Oberon.

Unknown Origins of Carbon Oxide Enrichment

Forty years ago, the Voyager 2 spacecraft flew past Uranus and its twenty-seven moons, sending back prized portraits of the planet’s large and tidally locked satellites Miranda, Ariel, Umbriel, Titania, and Oberon. These images revealed extensive valleys, smooth plains, deep canyons, and possible icy volcanic (cryovolcanic) activity across the surfaces of the icy moons — the telltale signs of intense geologic activity. While Voyager 2 could take spectacular pictures, the spacecraft was not capable of identifying the molecules and materials making up these active surfaces.

Voyager 2 images of Uranus’s six largest moons. Click to enlarge. [NASA / JPL-Caltech / Ted Stryk; CC BY-NC-ND 4.0]

Ground-based detections are limited due to contamination from Earth’s atmosphere as well as the overall weakness of the carbon dioxide spectral features, thus space-based near-infrared observations of the Uranian moons are necessary to better constrain the carbon oxides on the satellites. Luckily, JWST’s Near-Infrared Spectrograph (NIRSpec) now offers astronomers unimpeded access the moons’ carbon oxide spectral features.

Chemical Clues from Space and in the Lab

In 2024, a study acquired NIRSpec observations of Uranus’s moon Ariel, revealing prominent carbon dioxide features and confirming the presence of carbon monoxide ice hinted at by ground-based studies. Expanding on these observations to include Umbriel, Titania, and Oberon alongside Ariel, Richard J. Cartwright (Johns Hopkins University) and collaborators obtained JWST NIRSpec spectroscopy of Uranus’s four largest moons in hopes of disentangling the origin story of their carbon oxides.

Diagram illustrating the leading and trailing sides of a moon orbiting Uranus. Click to enlarge. [AAS Nova/Kerry Hensley]

Spectral ratios of the trailing and leading hemispheres for each moon, labeling spectral features of multiple carbon-bearing molecules. Click to enlarge. [Cartwright et al 2026]

Carbon Oxide Origins

What does this mean for the origins of the carbon oxides on the Uranian moons? Spectral features of carbonate minerals and the widespread presence of carbon dioxide throughout the Uranus system suggest that these compounds exist natively. On the other hand, the concentration of carbon oxide features on the trailing hemispheres supports radiolytic production as these hemispheres are bombarded with more ionizing particles from Uranus’s magnetosphere.

Based on these results, the authors have postulated that both origin scenarios, native presence and radiolysis, are required to fully explain the presence of carbon oxides. Future laboratory studies and JWST observations will continue to reveal the nature and composition of bodies in the Uranus system, furthering our understanding of our solar system siblings.

Citation

“Tracing the Source of Carbon Oxides on the Large Moons of Uranus,” Richard J. Cartwright et al 2026 Planet. Sci. J. 7 199. doi:10.3847/PSJ/ae8818

The post Breaking the Ice: Origins of Carbon Oxides on Uranian Moons appeared first on AAS Nova.

Light and dark regions speckle the Sun and other stars, complicating the interpretation of exoplanet transmission spectra. New modeling suggests that faculae — bright areas on the visible surface of the Sun — appear dark on cooler stars, adding a new wrinkle to this challenge.

Dark Spot, Bright Spot

This image from the Daniel K. Inouye Solar Telescope shows solar convective cells called granules. The bright points in the dark lanes between granules are regions of enhanced magnetic field strength. [NSO/AURA/NSF; CC BY 4.0]

The Sun is freckled with dark spots — sunspots — as well as bright regions called faculae. Sunspots form where the Sun’s magnetic field bubbles up, creating pockets of cooler, less luminous plasma. Solar faculae form in regions of concentrated magnetic field, creating bright spots that line the dark crevasses between convective cells.

Other stars also have starspots and faculae, but thus far, astronomers have no direct observations of faculae on any star except the Sun. Out of necessity, researchers interpreting exoplanet spectra assume that faculae on other stars are similar to those on the Sun — but are they actually?

Would a Facula on Any Other Star Look as Bright?

To explore what faculae might look like on stars other than the Sun, Alexander Shapiro (University of Graz; Max Planck Institute for Solar System Research) and collaborators turned to three-dimensional radiative magnetohydrodynamics simulations and radiative transfer modeling. Their aim was to simulate the appearance and spectra of faculae on stars of spectral type G2, K2, M0, and M4 — from Sun-like to substantially smaller and cooler than the Sun.

Simulated faculae on a Sun-like star (left) and an M4 star (right). These images show the faculae at 600 nm. Click to enlarge. [Shapiro et al. 2026]

Exoplanetary Effects

The transition from bright faculae on Sun-like stars to dark faculae on M4-class stars directly affects interpretations of exoplanet transmission spectra. The existence of dark faculae increases the derived exoplanet radius, whereas bright faculae on Sun-like stars decrease the derived radius. The contamination due to the faculae is wavelength dependent, with the largest contamination occurring at shorter wavelengths. This contamination, if not fully accounted for, can mimic spectral features from an exoplanet’s atmosphere.

Contamination of transmission spectra by faculae near a star’s poles (left) and closer to the star’s equator (right). Faculae are bright for the simulated G2, K2, and M0 stars, and they are dark on the simulated M4 star. Click to enlarge. [Shapiro et al. 2026]

Citation

“The Curious Case of Dark Faculae on M Dwarf Stars,” A. I. Shapiro et al 2026 ApJ 1008 24. doi:10.3847/1538-4357/ae7105

The post When Bright Spots Go Dark appeared first on AAS Nova.

Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

Title: Thermal Electrons in the Radio Afterglow of Relativistic Tidal Disruption Event ZTF22aaajecp/AT 2022cmc
Authors: Lauren Rhodes et al.
First Author’s Institution: McGill University
Status: Published in ApJ

Tidal disruption events (TDEs, see Figure 1), which occur when a star gets a little too close to a supermassive black hole (SMBH) and gets ripped apart, are a hot topic across the electromagnetic spectrum. During a TDE, the star can no longer hold itself together under the gravitational pull of the SMBH. Some bits of the star end up accreting onto the black hole, which can launch a temporary outflow, or, in especially dramatic cases, a relativistic jet.

Figure 1: Timeline of events leading to a tidal disruption event. [Chloe Klare]

How to Spot a TDE

Usually, TDEs are discovered in the X-ray (after all, not many transients are powerful enough to generate an X-ray flare) or in the optical (thanks to high-cadence, wide-field surveys like the Zwicky Transient Facility and the Legacy Survey of Space and Time). However, radio is a particularly useful regime for TDE searches, especially in dusty host galaxies where we cannot see the optical TDE signatures at all; while dust obscures optical light, the radio is unaffected! There is just one catch: how exactly can we identify a TDE based on only its radio emission?

The radio light in a TDE is generated via synchrotron radiation — which is caused by fast moving electrons in strong magnetic fields — and originates in jets or shocks. Unfortunately, this is also the case in AGN, the primary extragalactic source of variable radio emission, and it can be difficult to distinguish between the two. Additionally, the amount of light we see from synchrotron radiation at a given frequency depends on how energy is distributed among the electrons in the source, which is unknown. Perhaps the simplest case — or at least the one you’ll learn about first in your undergraduate statistical mechanics course — is that the energy is distributed among the electrons thermally (left panel in Figure 2). However, most radio transients associated with black holes are assumed to have non-thermal electron energy distributions, usually where there are exponentially many more low-energy electrons than high-energy electrons (right panel in Figure 2).

Figure 2: Energy can be distributed among the electrons in a source either thermally (left panel), where most electrons have a medium amount of energy, or non-thermally (right panel), where most electrons have a small amount of energy. Often, extragalactic radio transients are assumed to originate from non-thermal electrons, but today’s article argues why we shouldn’t ignore thermal electrons. [Chloe Klare]

This includes today’s authors, who have focused on one particular TDE, ZTF22aaajecp/AT2022cmc (I’m sure everyone mispronounces her name), or 2022cmc for short. 2022cmc is a special TDE: it is one of only five TDEs suspected to have launched a relativistic jet, and it has the highest redshift (z ~ 1.2) of the five. It was observed first in the optical and then in the X-ray and radio. The X-ray emission was highly variable for 400 days post-TDE, and then disappeared, and the first 100 days of radio emission indicated there was a relativistic outflow. At the time, it was concluded that the jet shut off and the X-ray emission ceased. However, the story doesn’t end there; the authors of today’s article continued to observe 2022cmc in the radio for an additional 900 days at frequencies spanning about 1–100 GHz.

Our authors had two key observing strategies: wide frequency coverage and long duration. Measuring the change in brightness with observing frequency, or the spectral energy distribution (SED), is important for determining which processes are responsible for the radio emission, since thermal electrons and non-thermal electrons will produce different SEDs. On the other hand, measuring the change in brightness over time, or the light curve, is important for determining what is happening at the source, such as whether there is a jet and, if so, how long it lasts. Here, our authors combine light curves at six different frequencies (Figure 3) and SEDs at nine different epochs (Figure 4) to investigate both.

Figure 3: Light curves spanning six frequencies and 900 days obtained by today’s authors. [Rhodes et al. 2025]

Figure 4: Nine epochs of radio SEDs, which show the peak moving to lower frequencies over time. [Rhodes et al. 2025]

The Findings

Our authors find a couple of interesting results. First, in the time domain, they find the highest-frequency light curves fade with time, while the lower-frequency light curves increase initially, hit peaks at different times (after 300 days at 15.5 GHz, and after 800 days at 1.3 GHz), and then begin to decay. The spectral evolution is even more intriguing; the SED is always peaked, and the peak shifts to lower frequencies over time, which is typical for an expanding emission region. At frequencies below the peak, the SED doesn’t change much. However, the high-frequency side of the SED shows confusing behavior: early on, it has a very steep slope (the amount of light drops off sharply at higher frequencies), but it eventually flattens.

Investigations Begin

Next, our authors consider three possibilities to explain these observations. They first consider synchrotron radiation from only non-thermal electrons in a relativistic jet (Figure 5), which is the canonical model for a gamma-ray burst radio afterglow. Initially, the jet is so fast that all its radio light is relativistically beamed in one direction (like a flashlight), and we can only see the jet if it’s pointed directly at us. Eventually, the jet slows down enough that it is no longer beamed, and light is emitted in all directions (like a light bulb). At this point, we see the light fade over time, which is exactly what happened in the high-frequency light curves. However, there is one glaring problem: this model cannot possibly explain the observed long-lasting steep SED at high frequencies. So, our authors discard this theory.

Figure 5: The left image shows what a black hole–generated jet looks like in the rest frame of the jet itself. As long as the jet isn’t moving too fast, this is what we see too. However, if the material in the jet is moving near the speed of light, we observe a relativistically beamed jet (right image). [Chloe Klare]

Lastly, our authors keep the thermal/non-thermal electrons combo and ditch the jet entirely, modeling a spherical outflow. Excitingly, this model best fits the observations, and, most importantly, can explain the mysterious high-frequency behavior. Initially, most of the radio emission originates in the thermal electron population, which produces more light at higher frequencies. As the outflow expands, the non-thermal electrons begin to dominate, and the SED transforms into the classic non-thermal synchrotron shape.

Next Steps

Ideally, our authors want to compare 2022cmc to other TDEs, but few TDEs have such thorough follow-up observations. They speculate that thermal electrons were important in the radio evolution of one of the few such TDEs, Swift J1644, and recommend we revisit its emission models. More broadly, they recommend two future priorities: first, we need extensive radio observations for larger samples of TDEs, especially around 100 GHz, where the thermal electrons contribute most to the SED; secondly, we should stop neglecting thermal electrons not just in TDE models, but in models of any black hole jets, including gamma-ray bursts and X-ray binaries. While this work addresses only one event, one thing is clear. For theorists and observers alike, there is a myriad of exciting work to be done, so it’s no wonder TDEs have garnered so much attention lately.

1. A convenient property of extragalactic synchrotron sources is that all their electrons radiate independently of one another, even if they are part of the same electron population. This is called incoherent emission. (Galactic sources are another story, but I’ll save that for another time.) ︎

Original astrobite edited by Flavia Pascal.

About the author, Chloe Klare:

I’m a PhD student in astronomy and astrophysics at Penn State (with a physics minor, so I get to use my semester spent in QFT for something!). I study active galactic nuclei (in the radio!), and I’m currently looking for baby synchrotron jets in active galactic nuclei.

The post Thermal Electrons Can Explain the Mysterious Radio Behavior of a Tidal Disruption Event appeared first on AAS Nova.

A planned flagship spacecraft to Uranus was aiming to use Jupiter for a gravitational boost to shorten its journey to the outer solar system. Now that the mission’s launch date has been pushed back, it’ll need to find another way to its target.

Redesigning the Route

Uranus and Neptune, the ice giants of our solar system, have been comparatively neglected by humanity’s fleet of interplanetary probes. While all of the other major bodies have been visited by at least an orbiter or even a lander, the most detailed exploration we’ve done of these two planets happened when the Voyager 2 spacecraft went screaming past on its way toward interstellar space.

Schematics of different trajectories within the solar system. Left: The path the Galileo spacecraft took to Jupiter. This path arrived nearly parallel to the planet’s motion. Right: One of the proposed paths to Uranus. This path will intersect the planet’s orbit at a much steeper angle to shorten the flight time. Click to enlarge. [Simon et al. 2026]

Getting these spacecraft to their destination will be a challenge The thriftiest path to get to Uranus, a trajectory called a Hohmann transfer that’s been used for other missions aimed elsewhere in the solar system, would take 16–17 years. Rather than accept the long wait, the original authors suggested that the mission instead fly toward Jupiter, using the giant planet’s massive gravitational tug to slingshot the spacecraft toward Uranus.

However, this plan relied on Jupiter being in just the right place when the spacecraft approached. This in turn relied on the mission launching sometime in 2031 or 2032: any earlier or later, the slingshot would be aimed in the wrong direction. Now that timelines and budgets have slipped for this flagship mission, hitting this launch window seems unlikely. And, without the boost from Jupiter, the mission will have to cross 20 au of open interplanetary space on its own.

Solar Electric Propulsion to the Rescue

Several proof-of-concept designs for the mission’s SEP components. How these designs would be packaged into a rocket fairing for launch is shown at right. Click to enlarge. [Simon et al. 2026]

The power levels would likely get too low just a few astronomical units into their journey, but that would be enough: after discarding the SEP stage, the mission could coast to Uranus on a journey that would take only 13 years. Even better, this technology has a proven flight history and would require little maturation or development. The BepiColombo mission to Mercury is currently using SEP, and similar techniques are used on satellites in Earth orbit today.

Simon and collaborators also took on a number of other challenges that have cropped up since the mission was proposed, including fewer available plutonium power sources and a re-assessment of Uranus’s rings that revealed hazards in the original flight path. Their work brings the mission closer to the launch pad and illustrates how much iteration goes into the spacecraft that finally takes to the stars.

Citation

“Uranus Orbiter and Probe: Mission Challenges and Concept Updates Since the Origins, Worlds, and Life Decadal Survey,” Amy A. Simon et al 2026 Planet Sci. J. 7 143. doi:10.3847/PSJ/ae680c

The post Who Needs Jupiter? appeared first on AAS Nova.

While previous investigations of planet formation across the universe’s history suggest that planets trickled into the picture, a recent study has found that primordial planetesimals could have formed much earlier from the insides of the first stars in the universe.

First Stars, First Planets?

When the first stars flickered on, the universe was filled with pristine gas, containing only hydrogen, helium, and a little lithium. This gas, though great at making massive stars known as Population III (Pop III) stars, was not yet enriched with the heavy elements necessary for planet formation and, of course, life. Past studies have suggested that planet formation in the universe was gradual, taking several billion years to peak after billions of stars created and spilled the needed metals into the universe. However, local pockets of enriched gas from Pop III stars could have created the right conditions for planet formation earlier in the universe’s history.

Pop III stars burned bright and fast, exploding violently in pair-instability supernovae that completely shredded the progenitor, ejecting over 100 solar masses of metals into their previously pristine surroundings. Cosmological simulations suggest that oxygen from these supernovae could have produced significant water fractions within the dense cores of the supernova remnant. This may have set the stage for planet formation in water-rich disks around subsequent generations of stars as early as 150–200 million years after the Big Bang — does numerical modeling support this planet formation hypothesis?

Simulation snapshots showing the formation and evolution of the protoplanetary disk for 13, 21, 30, 40, 50, and 60 thousands of years after protostellar birth. Click to enlarge. [Modified from Vorobyov et al 2026]

Primordial Planetesimals in Simulated Water-Rich Disks

To test if these water-rich dense cores within Pop III supernova remnants could form planetesimals, the building blocks of terrestrial planets, Eduard I. Vorobyov (University of Innsbruck; Southern Federal University) and collaborators performed numerical simulations tracing the collapse of one such gas core into a protoplanetary disk around a protostar. The simulations begin from the gravitational collapse of a 1-solar-mass gas cloud core, with a protostar emerging 24 thousand years after the initial cloud collapse. As the protostar’s gravity pulled in material from its surroundings, a rotating disk formed around the growing star.

Simulation snapshot 40 thousand years after the formation of the protostar showing the gas, dust, and planetesimal surface densities and the dust-to-gas ratio. Click to enlarge. [Modified from Vorobyov et al 2026]

Citation

“Planet Formation at Cosmic Dawn: Planetesimals in H₂O-rich Disks around Low-mass Stars,” Eduard I. Vorobyov et al 2026 ApJL 1007 L51. doi:10.3847/2041-8213/ae907c

The post Primordial Planetesimals from the Guts of Population III Stars appeared first on AAS Nova.

Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

Title: JWST Discovery of Warm Dust in the Circumgalactic Medium of the Makani Galaxy
Authors: Sylvain Veilleux et al.
First Author’s Institution: University of Maryland
Status: Published in ApJ

The Windy Galaxy

Billions of light-years away lies Makani, a record-breaking galaxy discovered in 2019 by researchers at the Keck Observatory atop Maunakea, Hawaiʻi. The galaxy shows evidence of a large merger event, where two galaxies collided to form a larger galaxy. This event triggered starburst activity, or several waves of intense star formation, that changed the makeup of not just Makani, but the region around it.

There are several processes that can create galactic winds. An active supermassive black hole at the center of the galaxy can slingshot particles out of the galaxy at close to the speed of light, or supernovae leftover from previous starburst activity can help to expel material from the galaxy. Makani, whose name in Hawaiian just so happens to mean “wind,” has both factors contributing to its galactic winds: massive amounts of star formation and a very active black hole in its center.

This contributes to some of the strongest galactic winds discovered to date, stretching approximately 100 kiloparsecs (330,000 light-years) beyond the galaxy, roughly ten times the extent of a typical galactic wind. These galactic winds remove gas from the galaxy and help to enrich the circumgalactic medium around the galaxy. There is still much to discover about how galactic winds change the makeup of such galaxies, and what exactly they take with them on their way out.

Earth’s Favorite Carcinogen: Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs, pronounced P-A-Hs or “paws”) are small flat dust grains scattered into every corner of the universe, from the atmosphere of Earth in the form of exhaust and wildfire smoke to the circumgalactic medium (the mostly empty space between galaxies). These PAHs contribute to regulating the temperature of the interstellar medium, but astronomers have long wondered how they migrate across galaxies.

Even though they are smaller than a human hair, PAHs are still easily observable even in very distant galaxies.  These dust grains emit infrared light, and if there are enough PAHs in a region, they are bright enough to be observed with modern telescopes, such as JWST. By combining multiple observations across multiple filters, astronomers can calculate ratios that reveal information about the PAHs’ size, temperature, and charge, allowing reserachers to further discern properties about the regions in which these PAHs reside.

With redshifted galaxies like Makani, the light from PAHs is stretched beyond its usual wavelength, but fortunately for today’s authors, the light was stretched just enough to land known PAH features well within JWST filters, as seen in Figure 1. The authors were then able to use this information to track the distribution of these PAHs across Makani.

Figure 1: Makani’s spectrum overlaid on top of the JWST filters. The peaks in the spectrum are PAH features that neatly overlap with JWST’s observing bands. [Veilleux et al. 2025]

PAHs Gone Extragalactic

Using JWST, the authors scrutinized Makani for any signs of PAHs. They found that not only did PAHs exist within the galaxy, these molecules were found up to 30 kpc (~100,000 light-years) outside the galaxy. Makani’s strong galactic winds were ejecting the dust grains from the galaxy over an estimated timescale of a billion years.

Previously, astronomers had not expected to find high quantities of dust grains outside the protection of a galaxy. The journey across a galaxy is long and hot, with temperatures in the millions of degrees. A dust grain would likely not survive the trip, as it would be destroyed by high-energy photons. This suggests that the PAHs were somehow shielded from the hotter parts of the interstellar medium and circumgalactic medium in large enough volumes to make it beyond the edge of Makani.

This answered questions about how galaxies enrich the circumgalactic medium, but it also added several more. Since today’s authors were limited by the sensitivity and range of their instruments, they were unable to confirm if there were PAHs along Makani’s entire wind structure, or just the first 35 kpc (114,000 light-years) of it. They also would like to turn their sights towards the intergalactic medium to see if PAHs could make it even farther beyond the reach of their host galaxy.

Original astrobite edited by Chloe Klare.

About the author, Natalie Price:

As a first-year master’s student at Wesleyan University, I study how stellar winds interact with the local interstellar medium. Outside of the observatory, you can find me dancing, with my nose in a book, or running at non-relativistic speeds.

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When a massive star collapses, the subsequent supernova can leave behind the star’s condensed core in the form of a neutron star. Some neutron stars are also pulsars, which rotate at incredible speeds, emit beamed radio emission, and expel winds of charged particles. A pulsar’s relativistic charged-particle winds billow around the pulsar as it travels through space — often at a few hundreds of kilometers per second or faster, having received a “kick” when its progenitor star exploded. When these winds interact with the surrounding supernova ejecta or the interstellar medium, the interaction creates a detectable pulsar wind nebula. The image above combines data from the Australian Square Kilometre Array Pathfinder (orange) and Wide-field Infrared Survey Explorer (cyan) to show a pulsar wind nebula, indicated with a white rectangle, within a larger supernova remnant. Sanja Lazarević (Western Sydney University) and collaborators discovered this pulsar wind nebula, which they’ve named “Thunder” in a nod to the supernova remnant’s moniker, “Nimbus.” The cometary shape of the pulsar wind nebula suggests that the pulsar is moving quickly, traveling outward from the center of the explosion that occurred some 30,000–45,000 years ago. To learn more about the discovery and characterization of this pulsar wind nebula, check out the article linked below.

Citation

“EMU Discovery of Thunder: A Bow-Shock PWN Powered by PSR J1631–4722 Escaping the Nimbus SNR (G336.7+0.5),” S. Lazarević et al 2026 ApJ 1007 159. doi:10.3847/1538-4357/ae7f11

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Astronomers have been measuring comets for centuries. But in December of last year, researchers collected a unique set of comet observations: they recorded some of the highest-quality data of one of the weirdest known comets while it was far from the Sun.

Simultaneous Spectra and Images

A few months after the famous interstellar comet 3I/ATLAS rounded the Sun and began its journey back into the space between the stars, a group of astronomers led by Nathan Roth (NASA Goddard Space Flight Center) aimed JWST in the direction of its retreat to watch it fade away. Using a special observing mode that leveraged the Integral Field Unit (IFU) in JWST’s Near Infrared Spectrometer, these observations didn’t result in just a single image of the comet, but a full stack of images, each corresponding to a different wavelength of light.

Using the IFU allowed the observers to combine the best of both regular imaging, which reveals spatial structure, and standard spectroscopy, which reveals wavelength dependencies. As a result, they could make spatially resolved maps of how the emission from the comet’s fuzzy atmosphere of gas and dust, or coma, changed with distance from the comet’s icy nucleus and angle to the Sun. Since different molecules radiate at different wavelengths, these maps in turn reveal the composition and geometry of 3I/ATLAS’s coma.

Mapping the Coma

The spectrum of the coma of 3I/ATLAS. Note that this is a real spectrum, not a simulation. The contributions of various molecules are labeled alongside their most prominent emission lines. Click to enlarge. [Roth et al. 2026]

First, in contrast with normal solar system comets where water is the most abundant molecule, water was actually a secondary player here: there was significantly more carbon monoxide, or CO, than water in 3I/ATLAS’s coma. The researchers note that this might not be representative of the true distribution of the two species, but instead be the result of the timing of these observations. When observing a standard solar system comet, astronomers usually examine their targets when the object in question is within 2 au of the Sun. At these close distances, solar radiation is strong enough that water ice dominates the outgassing and activity in a coma.

However, these IFU measurements were taken when 3I/ATLAS was about 2.4 au from the Sun, or right in the transition region where water doesn’t sublimate as easily as CO or carbon dioxide (CO₂). It’s likely that as the comet approaches the so-called “ice line” where water will naturally freeze out, CO will only increase its domination of the coma.

Top row: Maps of the distribution of various molecules in the coma. The white arrow shows the direction toward the Sun. Bottom row: The spatial distribution of the temperature of each species. Click to enlarge. [Roth et al. 2026]

Every Molecule for Itself

Second, each molecule seemed to be outgassing in its own unique direction from the coma. CO is leaving the nucleus in two different jets, one aimed directly back at the Sun and one perpendicular to it; CO₂ and methane (CH₄) are both leaking away in the anti-Sun direction; and water and methanol (CH₃OH) are sublimating in nearly spherically symmetric shells. The authors speculate that these geometries may be caused by different “active sites” on the comet, and that had they observed the comet for one full rotational period, they might have seen these jets pointing in different directions.

Although 3I/ATLAS is now too far and faint for observations like these, this study reveals just how much we can learn in the brief time interstellar visitors spend in our solar system. When the fourth interstellar comet inevitably wanders through the inner solar system, astronomers will doubtless be ready to use this observing mode again.

Citation

The post An Interstellar Comet’s Coma Composition appeared first on AAS Nova.

New research suggests that the circumplanetary disk surrounding the exoplanet PDS 70c contains a ring of dense dust, and the conditions within this ring may allow baby moons to form.

A Disk Within a Disk

A closeup of PDS 70c’s circumplanetary disk within PDS 70’s protoplanetary disk. [ALMA (ESO/NAOJ/NRAO)/Benisty et al.; CC BY 4.0]

There’s still debate over the exact source of the emission detected by ALMA. Does this emission come from dust, and if so, how is the dust distributed? Is the disk optically thick or optically thin? Does the emission even come from dust, or could it instead be free–free emission from unbound electrons navigating a charged-particle maze?

Dust Diagnosis

Yuhito Shibaike (Kagoshima University) and collaborators recently examined the hypothesis that the emission from PDS 70c’s circumplanetary disk arises from dust distributed in an optically thick ring. To test this hypothesis, the team explored two possible dust distributions, which they call “drift” and “ring.” In the drift model, dust grains within the circumplanetary disk migrate inward toward the planet, leaving much of the disk optically thin. Modeling suggests that this migration is typical in protoplanetary disks, and it might be common in circumplanetary disks as well.

Dust and gas surface density for the modeled disks in the drift (orange) and ring (blue) models. Click to enlarge. [Adapted from Shibaike et al. 2026]

Shibaike and coauthors found that the ring model naturally reproduced the observed spectral energy distribution for a range of reasonable parameters. The drift model, on the other hand, required an unrealistically high dust-to-gas ratio for the material accreted onto the circumplanetary disk from the parent protoplanetary disk to reproduce the observed spectral index.

Future Prospects and Moon-Making Possibilities

Comparison of ALMA observations (colored symbols) and model predictions (colored lines) from the drift (orange) and ring (blue) models. Click to enlarge. [Adapted from Shibaike et al. 2026]

Luckily, this likely won’t remain a mystery forever: the next-generation Very Large Array, which is anticipated to begin full science operations in the mid-2030s, should be able to resolve the location of the dust within the circumplanetary disk and illuminate the source of emission.

Finally, if the dust surrounding PDS 70c is concentrated within a ring, what does that mean for the possibility of moons forming within the disk? Shibaike and collaborators found that the conditions within the ring likely satisfy the requirements of both the streaming instability and the gravitational instability, which are required for dust grains to clump together and form the rocky building blocks of baby moons. Perhaps the PDS 70 system will one day be the site of not only a circumplanetary disk, but an exomoon as well!

Citation

“Interpreting ALMA Multiwavelength Continuum Observations of PDS 70 c: An Optically Thick Dust Ring in the Circumplanetary Disk,” Yuhito Shibaike et al 2026 ApJL 1006 L26. doi:10.3847/2041-8213/ae86f5

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Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

Title: Unbreaking the Universe: MINERVA Measurements of Color Gradients in Massive Quiescent Galaxies Can Help Ease Too-Early Star Formation Tensions
Authors: Sam E. Cutler et al.
First Author’s Institution: Tufts University
Status: Published in ApJL

Universe Breakers

JWST launched in 2021, and one of its key goals was to observe the first galaxies as they formed. Early results from JWST found something surprising: extremely massive galaxies in the early universe that had “quenched,” or stopped making new stars, much faster than was expected. These early results led some to believe that our understanding of how quickly massive galaxies can form and quench was fundamentally wrong.

Before concluding that our understanding of the universe is broken, it’s important to find other reasons why we might see very massive galaxies in the early universe. One theory is that these galaxies are actually less massive than we think. To “weigh” a galaxy, astronomers first measure the amount of light being emitted by that galaxy. If all the light in a galaxy comes from stars (which should be true in the early universe, though active black holes can contribute a lot of light in some galaxies), you can infer the total number of stars by accounting for the average amount of light emitted per star of a certain mass; this is called the “mass-to-light ratio.” Since massive stars emit a lot more light than low-mass stars, and high-mass stars die out faster than low-mass stars, the mass-to-light ratio is higher for older stellar populations. To accurately “weigh” a galaxy, scientists therefore need both a good measurement of the total amount of light in the galaxy and how old its stellar population is. The authors of today’s article suggest that the uncertainty in these measurements might be leading to overestimates of galaxy masses and underestimates of galaxy star formation rates, possibly explaining the existence of the earliest massive quiescent (non-star-forming) galaxies.

The Impact of Color Gradients

Previous works about the massive quiescent galaxies in this study used spectroscopy to determine the galaxies’ masses and star formation rates. These spectra were taken with a “slit,” which introduces a source of error: if the slit is smaller than the image of the galaxy, some of the galaxy’s light will be missed in the spectrum. Astronomers usually correct for this by checking how much of the total light of a galaxy image is covered by the slit and scaling up the spectrum to account for the missing light, but this correction assumes that the spectrum is basically the same across the entire galaxy.

However, this assumption is rarely correct. In the local universe, star-forming spiral galaxies like the Milky Way tend to be made of a central “bulge” surrounded by a “disk” (see Figure 1). The bulge is no longer actively forming new stars, leading to a red-to-blue color gradient as you move out from the center of the galaxy. In astronomy, this is considered a “negative” color gradient. A slit that only covers the galaxy center would lead to an overall overestimate of the stellar mass and underestimate of the star formation rate. If the galaxies instead had a positive color gradient, with more star formation in the center of the galaxy, the mass would be underestimated and the star formation rate would be overestimated. Galaxies with both positive and negative color gradients have been found in the distant universe. By measuring the color gradient for each individual galaxy in their sample, the authors can correct the mass and star formation rate calculations from spectra taken with a slit spectrograph.

Figure 1: The spiral galaxy NGC 2683 with its bulge and disk labeled. The inner part of the galaxy (“bulge”) contains older, redder stars; the outer part of the galaxy (“disk”) contains bright blue stars that indicate that star formation is ongoing. Here, the slit spectrograph only covers the galaxy’s bulge, leading to incorrect mass and star formation rate measurements. [ESA/Hubble & NASA (CC BY 4.0) with annotations by Margaret Verrico]

Results

Instead of using spectra, the authors of today’s article use imaging in different filters to measure color gradients for a sample of four galaxies in the early universe that had previously been found to be extremely massive and no longer forming stars. They use medium-band filters, or filters that let in only a small part of a galaxy’s spectrum, to produce a spectral energy distribution at each radius. This spectral energy distribution is less informative than a spectrum (think a handprint versus a fingerprint), but it’s detailed enough to model the likely stellar population at each radius to determine whether the galaxies have positive, negative, or no color gradients, allowing for better corrections to the properties measured from the galaxies’ centers. They also model the stellar population from the central part of the galaxy that would normally be covered by a slit, as well as from the actual spectrum, to test whether any differences in their results come from their choice of modeling techniques.

The authors find that three of the four galaxies have a negative color gradient in at least some areas. The fourth galaxy has a relatively flat color gradient, though this measurement is less certain due to the object’s redshift. When the authors plot the galaxies’ colors on a diagnostic diagram that separates red and old galaxies from young and blue galaxies, they find that three of the four galaxies have centers that appear red and old but outskirts that appear young and blue (Figure 2). This means previous measurements of the mass may have been overestimated, and previous measurements of the star formation rate may have been underestimated.

Figure 2: The location of each of the four galaxies on a color–color diagram that separates red galaxies (above/to the left of the dashed lines) from blue galaxies (below/to the right of the dashed lines). The open markers indicate the galaxy color as measured from the center of the galaxy; the filled-in markers show the color at different radii from the galaxy center. For all but one galaxy, the color at several radii is bluer than at the center, indicating that the galaxy might have younger stars at least at some radii. [Adapted from Cutler et al. 2026]

Is the Universe Broken?

To determine whether these galaxies still count as “universe breakers,” the authors use a cosmological model to predict the largest expected galaxy mass in the observed area at different periods in cosmic time. The previous results had less than a 0.3% chance of occurring under current cosmological models; with their updated numbers and stellar population models, the authors find that the observed galaxies sometimes have more than a 5% chance of occurring, though there is still tension. They point out that their analysis ignores processes that could help galaxies grow and quench in the early universe, like galaxy mergers; still, the existence of these massive galaxies with such low star formation rates remains a puzzle.

Original astrobite edited by Ansh Gupta.

About the author, Margaret Verrico:

I am a fourth-year graduate student at the University of Illinois Urbana-Champaign. I study the connection between supermassive black hole transients and their host galaxies. I am also an avid knitter and reader, and I am passionate about opening up STEM opportunities for people of all backgrounds.

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The supernova remnant W50 — nicknamed “the Manatee” because its blobby radio emission resembles an aquatic mammal floating through starry waters — harbors an extreme system at its heart. Near the center of the remnant, the microquasar SS 433 exhibits an immense pair of relativistic jets, likely powered by a stellar-mass black hole accreting material from a companion star. In the image of W50/SS 433 above, radio emission is in red, optical light is in yellow, and soft, medium, and hard X-ray emission are in green, cyan, and magenta, respectively. Brydyn Mac Intyre (University of Manitoba) and collaborators focused on the region circled above, using NuSTAR and XMM-Newton to understand the source of the X-ray emission in that region and the potential for SS 433 to accelerate particles to relativistic velocities. These observations suggest that W50/SS 433 accelerates electrons up to energies of more than 100 teraelectronvolts, and it may launch other particles into the highly sought-after petaelectronvolt range. To learn more about the particle-acceleration possibilities in this remarkable region, be sure to check out the full research article linked below.

Citation

“The Western Jet of SS 433/W50: Hard X-Ray Emission, Spectral Evolution, and Comparison to the Eastern Jet,” Brydyn Mac Intyre et al 2026 ApJ 1006 69. doi:10.3847/1538-4357/ae7a47

The post Featured Image: The Microquasar and the Manatee appeared first on AAS Nova.

Exactly how the universe became reionized after cooling to form stars and galaxies remains an open question. A recent study investigates how a merging set of galaxies may have spurred an onslaught of ionizing photons into the intergalactic medium.

Lyman Continuum Leakers and Merging Galaxies

After its chaotic and blistering beginning, the universe cooled and began to coalesce, stars and galaxies flickering on to set the universe alight. From a few hundred million to about a billion years after the Big Bang, galaxies pumped high-energy ionizing Lyman continuum (LyC) photons into the intergalactic medium during what is known as the epoch of reionization. The exact mechanisms that produced and allowed LyC emission to escape galaxies during this era remain elusive.

Hubble Space Telescope image of the interacting galaxy group Arp 194. The blue stream connecting the galaxies is where tidally stripped gas formed millions of new stars. [NASA, ESA, and the Hubble Heritage Team (STScI/AURA)]

While observational studies have increasingly pointed to galaxy mergers as considerable drivers of LyC escape, only a small number have explicitly considered the role of mergers in the epoch of reionization due to spectral and spatial resolution limitations. Leveraging the high-resolution capabilities of JWST, Shengzhe Wang (University of Chinese Academy of Sciences; National Astronomical Observatories, Chinese Academy of Sciences) and collaborators performed detailed analyses of two LyC-leaker candidates to better understand the role of galaxy mergers in heating up the universe.

Confirming (and Refuting) Merger-Driven Leaks with JWST

Using candidate LyC leakers first identified in the LymAn Continuum Escape Survey (LACES) carried out with the Hubble Space Telescope, Wang and team obtained high-resolution JWST spectroscopy for two galaxies at redshift z = 3.1 (about 2 billion years after the Big Bang), LACES94460 and LACES104037. After carefully identifying and measuring emission lines in each candidate, the authors confirmed LACES104037 as a merger-driven LyC leaker. However, the apparent LyC emission from LACES94460 was determined to be contamination from a low-redshift object.

Hubble and JWST observations of LACES104037. The top panels show the Hubble images (first two panels) and the JWST spectral observations (last three panels). The bottom panel shows a composite three-color image marking the location of two primary interacting galaxies and the LyC emission along with the associated spectra. Click to enlarge. [Wang et al 2026]

LACES104037-LyC represents the first confirmed LyC leaker of its kind: an external clump of star formation in a tidal tail. This discovery aids in our understanding of how mergers can drive high-energy photon emission, and highlights the critical role galaxy mergers may play in the epoch of reionization. Future high-resolution observations will hopefully reveal more knots of LyC-leaking stars within merging galaxies and provide a deeper understanding of this important evolutionary phase of the universe.

Citation

“Confirmation and Refutation of Lyman Continuum Leakers at z ~ 3 with JWST NIRSpec IFU,” Shengzhe Wang et al 2026 ApJL 1006 L17. doi:10.3847/2041-8213/ae8523

The post A Lyman-Leaking Galaxy Merger Confirmed with JWST appeared first on AAS Nova.

Ultra-hot Jupiter WASP-121b is once again puzzling astronomers. New JWST observations have revealed aspects of this superheated planet’s atmosphere that models cannot yet explain.

An Extreme Planet

Among the more than 6,000 known exoplanets, there are many types of worlds that aren’t represented in our solar system. The most exotic and unfamiliar planets might be the ultra-hot Jupiters: giant planets nestled so close to their host stars that they are tidally locked, with temperatures on their permanently starlit sides climbing to thousands of degrees.

WASP-121b, which circles its F-dwarf host star every 30.5 hours, is one of the best-studied ultra-hot Jupiters. Previous work has started to reveal the complexity of its atmosphere, and now, data from JWST have opened a new window onto WASP-121b’s behavior.

New View from JWST

A representation of an exoplanet’s phase curve. Click to enlarge. [ESA]

The team used two 3D general circulation models to predict the planet’s atmospheric structure and extract synthetic spectra and phase curves to compare against the JWST observations. Using nine model configurations in total, the team varied several inputs, including sources of atmospheric opacity, sources of atmospheric drag, and assumptions about whether clouds are able to form on the planet’s cooler nightside.

Left with a Mystery

Frazier and collaborators found two aspects of WASP-121b’s phase curve that their models couldn’t explain: the planet emits less light overall than predicted, and the location of its phase-curve offset changes with wavelength.

Modeled phase curves, shown as the flux of the planet divided by the flux of the star, for WASP-121b (colored solid and dotted lines) compared to the best fit to the JWST observations (black line). Click to enlarge. [Frazier et al. 2026]

The phase-curve offset is the difference between a planet’s sub-stellar point (where the star is directly overhead) and the brightest point in the planet’s atmosphere. In general, some degree of offset is expected because planetary winds tend to whisk heat away from the sub-stellar point, placing the brightest point somewhere to the east (usually). For WASP-121b, the offset is unexpectedly small — suggesting a source of drag in the atmosphere that prevents winds from transporting heat away from the sub-stellar point — and it’s larger at shorter wavelengths. This wavelength dependence isn’t predicted by any of the models, and it’s not clear what causes it.

These results demonstrate something remarkable: that our observations of a planet nearly 900 light-years away have become so precise that they’re pushing our already complex models to include more physics — an exceptionally exciting motivation for model improvement!

Citation

“The Days Drag On on WASP-121 b: Interpreting Its NIRISS Spectroscopic Phase Curve with General Circulation Models,” Robert C. Frazier et al 2026 ApJ 1004 102. doi:10.3847/1538-4357/ae69ca

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In 2010, the supernova SN 2010jl illuminated a corner of a small, irregular galaxy 150 million light-years away. More than a decade later, researchers have found evidence that this collapsing massive star has created a significant amount of cosmic dust.

Superluminous Supernova

This X-ray and optical image shows SN 2010jl in its host galaxy. The supernova is the brightest X-ray source, near the top of the galaxy. [X-ray: NASA/CXC/Royal Military College of Canada/P.Chandra et al); Optical: NASA/STScI]

SN 2010jl offers an excellent chance to study the dust-forming potential of core-collapse supernovae. This supernova was unusually luminous because of intense interactions between the expanding supernova shock and the dense material surrounding the exploding star, and it’s possible that these types of interactions spur the creation of dust. In the first few years after the supernova was discovered, researchers found evidence that it had produced new dust. What has it been up to since?

SN 2010jl’s inferred dust mass over time (black stars) compared to other supernovae. Click to enlarge. [Smith et al. 2026]

Checking Back In

Thirteen years after SN 2010jl was discovered, Nathan Smith (Steward Observatory) and collaborators checked in on its dust production. The team collected new ground-based optical spectra from the Keck I telescope and the MMT Observatory and mid-infrared spectra from JWST. The optical spectra — among the latest collected for any superluminous supernova — show numerous narrow emission lines that indicate that the expanding supernova continues to interact with its surroundings.

In the JWST observations, SN 2010jl is the brightest mid-infrared point source in its host galaxy. Through spectral energy distribution modeling, Smith and coauthors found that the brilliant infrared emission is likely due to a shroud of warm dust totaling roughly 20% of the mass of the Sun. This is about 80 times more dust than inferred from observations made a decade earlier.

Where’s the Dust?

Diagram showing the outward-moving forward shock and inward-moving reverse shock of a supernova that is interacting with the interstellar medium (ISM). The post-shock region is located between the two shocks and contains shocked ejecta as well as shocked interstellar material. Click to enlarge. [AAS Nova/Kerry Hensley]

While it’s not possible to rule out the other options entirely, Smith and collaborators argue that at least some of the dust can be traced to new growth in the post-shock region. Because post-shock dust grains are likely to reach the interstellar medium, this suggests that superluminous, strongly interacting supernovae like SN 2010jl are a viable source of dust in the present-day universe and in high-redshift galaxies alike.

Citation

“JWST Spectra Indicate a Large Mass of Postshock Dust Formed by SN 2010jl,” Nathan Smith et al 2026 ApJ 1006 224. doi:10.3847/1538-4357/ae74c5

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Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

Title: Geometry, Not Calorimetry, Drives the Radio–Infrared–γ Ray Correlation
Authors: T. A. Porter, I. V. Moskalenko, and G. Jóhannesson
First Author’s Institution: Stanford University
Status: Published in ApJ

Galaxies emit light not only in the visible band, but also across other wavelengths via different physical mechanisms. Finding correlations between emissions at different wavelengths is a powerful tool for astrophysicists to explore the underlying mechanisms of galaxy formation. One of the most famous examples is the infrared–radio continuum correlation, which holds across several orders of magnitude in luminosity.

The typical explanation for this correlation is that both infrared light and radio synchrotron emission share the same energetic origin: star formation. Young stars emit ultraviolet radiation, which is absorbed by interstellar dust and re-radiated in the infrared. When these stars end their lives in core-collapse supernovae, the resulting shock waves accelerate cosmic-ray electrons, which then interact with the magnetic field to produce synchrotron emission.

For this correlation to hold, cosmic-ray electrons must radiate away all their energy within the galaxy, unable to escape and carry away some of their energy. Otherwise, the amount of radio emission would depend on how quickly cosmic rays escape and would no longer correlate with the infrared emission. This assumption is called the “electron calorimeter” model, which assumes that electrons lose all their energy due to radiation without escaping the galaxy. However, observations show that the infrared–radio correlation persists even in low-density galaxies where cosmic rays can easily escape, suggesting that the calorimeter model may not be the full story. To reconcile this, previous studies proposed “conspiracy-like” scenarios in which cosmic-ray injection, transport, magnetic-field amplification, and gas density are all coupled in a finely self-regulating way to maintain the correlation across diverse galactic environments — a somewhat awkward explanation that requires multiple unrelated physical processes to conveniently work together.

With the increased sensitivity of the Fermi Large Area Telescope, high-energy gamma-ray (or γ-ray) detections add new information to this picture. A galaxy’s γ-ray emission is produced by two different sources: cosmic-ray protons interacting with the interstellar medium gas, and cosmic-ray electrons inverse-Compton scattering off of nearby starlight or photons from the cosmic microwave background. Since both processes involve cosmic rays, the total γ-ray emission should also reflect the amount of star formation and therefore correlate with infrared and radio emission.

Because all three wavelengths trace different pieces of the same cosmic-ray population, studying them together reveals how the galaxy’s total cosmic-ray energy budget is distributed across its multi-wavelength emission.

The infrared–radio correlation has been established not only at the scale of entire galaxies, but also locally, down to patches roughly 100 parsecs across. Think of it like the relationship between a city’s electricity consumption and its population: we have long known they track each other city-wide, but it turns out the same relationship holds block by block. The infrared–radio correlation works the same way: zoom into any 100-pc region within a galaxy, and the correlation is still there. Unfortunately, the resolution of γ-ray observations is still stuck at around the kiloparsec scale. It is therefore unclear whether the local infrared–radio correlation reflects a genuine local physical coupling, one that would extend to γ-rays if we had sufficient resolution, or whether it is simply a spatial average of the emission, smoothed out by insufficient resolution. The answer determines whether radio and γ-ray emission can be used as reliable tracers of star formation, or whether they are just smeared out by cosmic-ray propagation over kiloparsec scales.

In this study, the authors numerically model galactic cosmic-ray transport, building a suite of physically motivated three-dimensional models of the Milky Way. They consider two variants for each of the four key inputs: 1) the cosmic-ray source distribution, 2) the interstellar gas, 3) the amount of starlight within the galaxy (the interstellar radiation field), and 4) the galactic magnetic field. Crucially, every model is normalized to reproduce the locally observed cosmic-ray data to within 5%, so that any differences in the predicted emission come purely from the large-scale geometry of each input, rather than from variations in the total cosmic-ray budget.

After evolving cosmic-ray transport for these realistic models, the authors then compute synthetic observations at radio, infrared, and γ-ray bands from various viewing inclinations to investigate how the underlying galactic model and the viewing angle affect the correlations between these emissions.

Surprisingly, inclination plays the most important role — more so than the cosmic-ray source distribution, the radiation field, or the magnetic field. Figure 1 shows the correlation plots between the radio and γ-ray emission (left two columns) and between infrared and γ-ray emission (right two columns) when viewing the galaxy face-on (i.e., viewing the galaxy from directly above the disk). Different colors represent γ-ray emission components from different physical mechanisms, with orange showing the total γ-ray emission. For both sets of correlation plots, starting from the upper-left panel, each panel modifies one physical input and recomputes the emission. Although there is some variation, one can see that the γ-ray emission correlates with both the radio and the infrared emission over several orders of magnitude, regardless of the underlying input model.

Figure 1: Radio (left two columns) and infrared (right two columns) vs. γ-ray correlation plots for a galaxy viewed face-on from 50 kpc. Each panel modifies one input — the cosmic-ray source distribution, gas, radiation field within the galaxy, or magnetic field — relative to a baseline model. Colors indicate γ-ray production mechanisms (green: proton–gas; black: inverse-Compton; orange: total). Across all variations, both the radio–γ-ray and infrared–γ-ray correlations remain quasi-linear over several orders of magnitude, showing that the correlations are robust to the choice of underlying galactic model. [Adapted from Porter et al. 2026]

In contrast, Figure 2 shows the correlation plot between radio and γ-ray emission (upper panels) and between infrared and γ-ray emission (lower panels) when viewing the galaxy edge-on (viewing the disk from the side). The radio–γ-ray correlation is preserved, while the infrared–γ-ray correlation is no longer observed. This is because, at this inclination, geometric projection separates the emission components. Infrared-emitting dust and γ-ray emission from cosmic ray–interstellar medium interactions are confined to the disk, while synchrotron radio emission and γ-ray emission from inverse-Compton scattering extend to larger distances above and below the disk. As a result, in an edge-on view, a sight line passing through the disk sees strong infrared emission, while a sight line that misses the disk sees zero infrared but still some γ-ray emission, breaking the infrared–γ-ray correlation. On the other hand, because radio emission is more extended than infrared emission, sight lines that miss the disk can still see both radio and γ-ray emission together, preserving the radio–γ-ray correlation.

Figure 2: Correlation plots for two galaxy models viewed edge-on from 50 kpc — simple axisymmetric (left) and complex with spiral arms (right). Top: radio vs. γ-ray; bottom: infrared vs. γ-ray. Colors indicate γ-ray production mechanisms (green: proton–gas; black: inverse-Compton; orange: total). The infrared–γ-ray correlation breaks down, while the radio–γ-ray correlation is broadened but partially preserved. [Porter et al. 2026]

However, there is one situation where the edge-on correlation comes back: when the observer is far enough away that the image becomes too blurry to resolve the galaxy’s internal structure. Figure 3 shows the same galaxy model viewed from 500 kpc, roughly the distance to Messier 31, our nearest large neighbor. At this distance, a single pixel in the image covers about 1 kpc, large enough for everything along the line of sight. The messy, broken-up pattern seen in the closer 50 kpc edge-on view (lower-right panel of Fig. 2) disappears, and a tight, nearly linear correlation comes back. This explains why nearly all distant, unresolved galaxies show tight radio–infrared–γ-ray correlations: the tightness is simply what you get when you blur everything together, not evidence that cosmic rays are actually losing all their energy locally inside those galaxies.

Figure 3: Correlation plots from a complex galaxy model viewed from 500 kpc, at three different inclinations (face-on, 45°, edge-on). Top row: radio vs. γ-ray; bottom row: infrared vs. γ-ray. Colors indicate different γ-ray production mechanisms (green: proton–gas; black: inverse-Compton; orange: total). At this distance, the blurring effect of large pixels restores a tight correlation even in the edge-on view. [Porter et al. 2026]

Now we have a consistent picture of the radio–infrared–γ-ray correlation: the authors conclude that this correlation is not a direct signature of cosmic-ray calorimetry, but a geometric projection effect. In face-on systems, a single sight line integrates emission from both the disk and off-disk regions, naturally producing a linear correlation, even when cosmic rays do not lose all their energy locally to radiation (i.e., local calorimetry is absent). In edge-on systems, the correlation breaks down because geometric stratification separates the different emission components. The practical implication is significant: for unresolved galaxies, the tightness of the global correlation alone cannot be used as evidence for cosmic-ray calorimetry, and the physically meaningful information about cosmic-ray transport and escape efficiency is encoded in the scatter around the mean trend, not in the correlation itself.

Original astrobite edited by Kelsie Taylor.

About the author, Sandy Chiu:

I’m a PhD candidate at the University of Michigan, Ann Arbor. I’m interested in numerical simulations of cosmic rays feedback in galaxies and their comparison with observation.

The post Do Galaxies Really Glow in Sync — or Are We Just Tilting Our Heads? appeared first on AAS Nova.

Only one white dwarf star has ever been caught eating an asteroid. Recently, however, astronomers may have found another that just finished its meal.

Eating Asteroids

Although stars like our Sun don’t explode in violent supernovae like their massive counterparts, they don’t slink quietly into a peaceful old age either. When a solar-mass star reaches the end of its main sequence life, it first swells dramatically (the Sun may eventually grow so large that it consumes Earth and the device you’re reading this on), then shrinks down to a tiny but incredibly hot ember known as a white dwarf.

An artist’s impression of an asteroid breaking up near a white dwarf star. [NASA, ESA, M.A. Garlick (space-art.co.uk), University of Warwick, and University of Cambridge]

However, although researchers have found these stains in over a quarter of white dwarfs and consequently have reasoned that asteroid snacking must be common, they’ve only ever caught one star mid-meal. Recently, Ben Zuckerman (University of California, Los Angeles) and a team of collaborators may have found another, though it may have just finished dining.

Leftover Crumbs

The light curve of WD J0234-0406 measured by the Zwicky Transient Facility. Unlike WD 1145+017, which frequently changes brightness, this white dwarf appears remarkably steady despite the high-velocity gas surrounding it. [B. Zuckerman et al. 2026]

The researchers suggest that this relative quiet is a matter of timing. While asteroids are actively breaking up around WD 1145+017, the parent bodies that supplied the gas and dust around WD J0234-0406 may have shattered long ago and have already been either vaporized or ground down into smaller particles. All that is left over are the crumbs slowly spiraling toward the star.

Although WD J0234-0406’s meal may not be as dramatic as WD 1145+017’s feast, it’s still exciting to expand the sample of known white dwarf-asteroid interactions. And, with the upcoming release of data from the DESI survey poised to reveal the spectra of tens of thousands of white dwarfs, the sample is likely to grow again soon.

Citation

“High-velocity Circumstellar Gas Orbiting a White Dwarf Star,” B. Zuckerman et al 2026 ApJ 1004 254. doi:10.3847/1538-4357/ae23c4

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Even the darkest corners of the universe are not completely empty. A recent study has used fast radio bursts to provide the first estimate of the baryon content in cosmic voids.

What’s in a Void?

Cosmological studies have revealed the large-scale filamentary structure of the universe known as the cosmic web. Chains of galaxies and galaxy clusters fall into spindly strands (or filaments) of matter overdensities, opening up cavernous cosmic voids that comprise the darkest corners of the universe. These seemingly vacant voids serve as critical test beds for cosmology, allowing researchers to constrain things like the nature of dark energy and the matter density of the universe.

Despite their name, voids are not completely empty but are instead underdensities with considerably less matter compared to the bustling filaments they border. The baryon (normal matter) content of cosmic voids has important implications for cosmological models and large-scale galactic feedback processes, but assessing how many baryons actually occupy voids has only recently become observationally accessible.

Sky maps centered on the north celestial pole showing the CHIME fast radio burst sample (top) and the SDSS void catalog (bottom). [Sharma et al 2026]

Chiming In on the Baryon Search

In concept, directly stacking fast radio burst sight lines that coincide with the positions of known cosmic voids provides a direct measurement of the baryon underdensity inside voids. With no previous observational exploration of this quantity, Kritti Sharma (California Institute of Technology) and collaborators leveraged the second catalog of the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Bursts (CHIME/FRB) sample in conjunction with the Sloan Digital Sky Survey (SDSS) Baryon Oscillation Spectroscopic Survey (BOSS) void catalog to provide the first observational assessment of the baryon underdensity in cosmic voids.

Anticorrelations between fast radio burst dispersion measures and void positions. There is a clear dispersion measure deficit closer to voids centers. [Sharma et al 2026]

This study provides a unique approach to baryon mapping and opens up the door for future investigation of cosmic voids. While not physically containing much, voids hold vast astrophysical and cosmological significance. With the astronomical stage primed with galaxy-mapping powerhouses like the Dark Energy Spectroscopic Instrument, Vera Rubin Observatory, Nancy Grace Roman Space Telescope, and Euclid Space Telescope, cosmic voids will become a cornerstone of cosmological studies.

Citation

“Baryons in the Darkest Sites of the Universe,” Kritti Sharma et al 2026 ApJL 1006 L3. doi:10.3847/2041-8213/ae81ac

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