New Webb and Hubble data not only confirm the existence of two distinct populations of stars in the ancient stellar system Terzan 5, once classified as a globular cluster, but also provides evidence for two more recent rounds of star formation.
The post Astronomers Find Four Separate Generations of Stars in ‘Globular Cluster’ Terzan 5 appeared first on Sci.News: Breaking Science News.
JCMT0402-0424, a dusty starburst galaxy around 11 billion light-years away, is the strongest candidate yet for the source of the high-energy neutrino event IC 210922A, according to a team of astronomer led by Yuji Urata of MITOS Science Co.
The post Astronomers Trace Elusive High-Energy Neutrino to Star-Forming Galaxy in Early Universe appeared first on Sci.News: Breaking Science News.
The James Webb Space Telescope (JWST) has revealed a cosmic catastrophe, as winds extinguished a star-forming galaxy in the early universe, offering new insight into earlier strange observations.
Cosmic winds may destroy entire galaxies, according to new JWST research exploring the lingering mystery of why certain parts of the universe are unexpectedly devoid of growth.
The findings were published in a recent paper in the Monthly Notices of the Royal Astronomical Society, revealing galactic-scale death in a universe just one billion years old, and potentially answering questions about previous troubling JWST observations.
Observations made by the JWST revealed cold gas, an essential star-forming material, blowing out of the CRISTAL-2 galaxy in a massive plume, severely degrading its ability to produce new stars. According to the researchers, it would take less than 50 million years for the galaxy to be completely dead if this activity keeps up, a mere blink in the scheme of a 13.8 billion-year-old universe.
Astronomers consider galaxies to be “dead” if they are no longer capable of producing fresh stars. Traditionally, astronomers expected that it would take billions of years for an old galaxy to slowly run out of fuel and burn out. However, JWST observations have continually captured events in the early universe that were not expected to occur until much later.
One of these was finding a host of dead galaxies in the early universe shortly after it first became operational in 2022. How galaxies could die so close to the beginning of the universe, without sufficient time to burn through their cold gas supplies, has long perplexed scientists.
As researchers began considering various explanations for the phenomenon, they initially settled on dark energy, essentially explaining one unknown with another. Dark energy is a theoretical substance that scientists believe drives the expansion of the universe and was once a stronger force than it is now. While the Dark Energy Spectroscopic Instrument survey revealed last year that dark energy appears to be weakening over time, an exotic galaxy-killer is not required, according to this latest research.
Instead, researchers offer a much simpler explanation of powerful cosmic winds in the remote past. Conventional thinking has it that such powerful winds could only be generated by a supermassive black hole, yet these new observations challenge that assumption.
CRISTAL-02 is a galaxy still in the making, composed of several smaller galaxies in the final stages of merging into a single system. Because the early universe was far denser than it is today, such collisions were much more common. During these mergers, gravitational forces funnel vast amounts of gas toward the galactic centers, triggering intense bursts of star formation.
Observations of CRISTAL-02 by the James Webb Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA) revealed a star formation rate roughly twice that of similar galaxies. Ironically, this extraordinary burst of stellar activity is also generating a powerful cosmic wind that is stripping away the very gas needed to form new stars.
Compounding the effect, many of the newly formed stars rapidly exhaust their fuel and end their lives as supernovae, producing additional outflows that further deplete the galaxy’s star-forming material.
Together, these processes appear capable of shutting down star formation far more quickly than astronomers previously believed possible. Going forward, ongoing JWST observations are likely to continue challenging astronomers’ assumptions, as more evidence indicates that nearly half of the early universe’s massive galaxies were interacting—a finding which also suggests early “galactic deaths” like these may not be all that rare, after all.
The paper, “Multiphase Images of a Powerful Supernova-Driven Wind in the Early Universe,” appeared in Monthly Notices of the Royal Astronomical Society on June 10, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.
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: Metal-Poor Star-Forming Clumps in Cosmic Noon Galaxies: Evidence for Gas Inflow and Chemical Dilution Using JWST NIRISS
Authors: Vicente Estrada-Carpenter et al.
First Author’s Institution: Arizona State University
Status: Published in ApJ
If you want to reconstruct a galaxy’s life story, one of the best “fossil records” is its metallicity. In astronomy this refers to the abundance of elements heavier than helium, which are made in stars and returned to a galaxy’s gas through winds and supernovae. Over time, more star formation usually means more metals mixed into the gas.
Now zoom to Cosmic Noon (roughly when the universe was most actively forming stars). Many galaxies in this epoch look “clumpy”; their star formation is concentrated in several bright knots scattered across the disk. The big question is where those clumps come from. Do they form from the galaxy’s own gas via internal disk instabilities, or do they light up when fresh, metal-poor gas flows in and both fuels star formation and dilutes the local metallicity?
The authors try to answer that question with JWST by measuring the metallicity of each clump relative to its immediate surroundings, rather than comparing clumps to a single galaxy-wide number (which can be misleading if the galaxy has a metallicity gradient).
They use JWST/Near Infrared Imager and Slitless Spectrograph (NIRISS) slitless grism spectroscopy from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS) to study 20 lensed galaxies at redshift 0.6 < z < 1.35. (Lensing effectively acts like a zoom lens, helping to resolve smaller structures.) They focus on emission lines that trace star-forming gas, especially Hα (a star formation tracer) and sulfur lines [SII] and [SIII] (needed for their metallicity method).
Slitless spectra come with a headache: because there is no slit, different parts of a galaxy can overlap in the dispersed image. To make reliable emission-line maps from slitless data, the authors use a forward-modeling code called Sleuth, which allows the continuum to vary across the galaxy.
The authors identify clumps using the Hα map together with rest-frame ultraviolet imaging because these tracers are sensitive to star formation on different timescales: Hα highlights gas ionized by the youngest massive stars, while ultraviolet light traces young stellar light over longer periods. As a result a clump can be bright in one and not the other, especially if dust is involved.
To estimate gas-phase metallicity, they use the “strong-line” method, which infers metallicity from ratios of bright emission lines calibrated using models and empirical samples. Their main diagnostic is S23 = ([SIII] + [SII]) / Hα. Because some line ratios also depend on the ionization state (how strongly the gas is being ionized by young stars), they also use the sulfur ratio S32 = [SIII]/[SII] as a check and iterate to a self-consistent solution.
For each clump, the authors measure the metallicity inside the clump and compare it to an annulus just outside the clump (masking neighboring clumps to avoid mixing). When they plot “clump metallicity” versus “local disk metallicity,” most points fall below the 1-to-1 line, meaning the clumps are more metal poor than their surroundings (Figure 1). The mean offset is about 0.1 dex, which corresponds to roughly 20% dilution in the clump gas.
Figure 1: Each point compares a star-forming clump’s gas-phase metallicity to the metallicity of the nearby disk region immediately surrounding it. If clumps and disks had the same metallicity, they would lie on the dashed 1-to-1 line. Instead, most clumps sit below it, showing a typical ∼0.1 dex metallicity deficit, consistent with local chemical dilution. (The solid red line shows a best-fit linear trend to the clump measurement.) [Adapted from Estrada-Carpenter et al. 2025]
If inflow is really the driver, you should expect a link: the more strongly a clump is forming stars relative to its surroundings, the more diluted its metallicity should be. That is exactly what the authors find. The clumps that are most boosted in star formation are also the most metal diluted.
The article also emphasizes that clumps are not chemically uniform blobs. In at least one detailed example, the peaks in Hα (highest star formation) coincide with local minima in metallicity along a cut through the galaxy (Figure 2), suggesting internal star formation rate and metallicity gradients that reinforce the same story, intense star formation goes hand in hand with lower metallicity in the clump regions.
Figure 2: Example galaxy from this study illustrating the clump-scale link between star formation and metallicity. The color image shows the galaxy with a rectangular strip marking the region used for a 1D cut. In the bottom panel, the turquoise line shows the Hα flux (a tracer of recent star formation), while the white line shows the metallicity along the same cut. Peaks in Hα flux line up with local dips in metallicity, showing that the brightest star-forming clumps are also the most chemically diluted compared to nearby regions. [Adapted from Estrada-Carpenter et al. 2025]
A reasonable alternative is that some clumps are actually small companion galaxies projected onto the disk. These could also look metal poor, because low-mass galaxies tend to be low metallicity. The authors look for evidence using face-on systems and find that more massive clumps tend to sit closer to galaxy centers, which is consistent with in-situ clumps that form in the disk and migrate inward, though it does not rule out satellites. They argue that kinematics from JWST/NIRSpec IFU will be needed for a definitive separation.
Gas inflow, star formation, and feedback, together known as the baryon cycle, are key drivers of how galaxies grow. What this article adds is a spatially resolved view that compares each clump to its local environment, showing that regions of elevated star formation also tend to be locally metal poor. That pairing is hard to explain as a simple metallicity gradient or a galaxy-wide averaging effect, and it is exactly what you would expect if at least some clumps are being fueled by relatively metal-poor inflows. In short, these clumps may be snapshots of galaxies refueling in real time.
Original astrobite edited by Ryan White.
About the author, Niloofar Sharei:
I’m an astronomy PhD candidate at UC Riverside studying how galaxies grow through star-forming clumps. I track how these clumps emerge, evolve, and sometimes survive long enough to reshape their galaxies. When I’m not thinking about cosmic blobs, I’m reading, hiking, or listening to Bach.
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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: Searching Within Galaxies for the Earliest Signs of Quenching With Spatially Resolved Star Formation Histories in UVCANDELS
Authors: Charlotte Olsen et al.
First Author’s Institution: New York City College of Technology
Status: Published in ApJ
Galaxies serve as important laboratories for many subfields of astrophysics. As such, astrophysicists are interested in the full galactic life cycle, from how galaxies are born to the end of their formation. Whereas young galaxies in the distant universe are actively forming stars, many nearby galaxies are much quieter, with little or no ongoing star formation. Astronomers like to describe these galaxies as “red and dead” because their stars are older and therefore appear redder in color. The process by which galaxies shut down their star formation is known as quenching, and it causes galaxies to become quiescent. Understanding the origin of quiescent galaxies is a fundamental question in galaxy evolution. Studying this process is challenging, however, because star formation is intertwined with many other factors that shape galaxies, including their environments and supermassive black holes.
Star formation occurs on scales that are much smaller and over timescales much shorter than the global properties and overall lifetime of a galaxy. By observing star formation on these smaller scales over time, astronomers can gain a clearer picture of how star formation ceases in a galaxy, and they can determine whether this process is driven from the inside out — starting with the supermassive black hole in the galactic center — or from the outside in, influenced by environmental effects. In today’s article, the authors use the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey with high-resolution ultraviolet coverage (UVCANDELS) to examine eight “golden” galaxies, shown in Figure 1. They then reconstruct the star formation histories within small regions of each galaxy to detect the “earliest signs of quenching.”
Figure 1: Images of the eight galaxies in the “Golden Sample” of galaxies studied in this work (right). These galaxies were chosen because of their clear detection, and they show a range of edge-on to face-on views as well as shapes. The authors divided each galaxy into small, resolved regions in which they measured the star formation (example shown on left). [Adapted from Olsen et al. 2026]
To trace a galaxy’s star formation over cosmic time, today’s authors model its integrated light — which encodes the many episodes of past star formation — using spectral energy distribution (SED) fitting. By comparing a galaxy’s light across many wavelengths to computer models, SED fitting can estimate the ages of its stars and when they formed. This approach allows astronomers to study how a galaxy’s star formation rate evolves as a function of its stellar mass, known as the SFR – Mstellar relation. Note that the article considers the star formation rate and stellar mass in individual regions of each galaxy, so it analyzes these properties as surface densities, ΣSFR and ΣMstellar, instead of the total values.
Using SED fitting, the authors determine the expected star formation rate and stellar mass of the regions from 250 million to 1 billion years before the time of observation. Figure 2 shows the line of best fit for the SFR – Mstellar relation of the regions for each galaxy, before and at the time of observation. The SFR – Mstellar relations are very similar across the sample 1 billion years before the observations; however, by the time of observation, the overall star formation rates have decreased slightly, indicating that the galaxies are beginning to quench. They also exhibit increased variation suggesting that each galaxy is quenching in a different way.
Figure 2: The best-fit SFR – Mstellar relation of the regions for each galaxy, represented by the different colored lines, 1 billion years (1 Gyr) before and at the time of observation (left and right panels, respectively). At 1 billion years before the observation, the galaxies appear to have the same relation, but their variation at the time of observation suggests that the galaxies have begun quenching in different ways. [Olsen et al. 2026]
Figure 3: The specific star formation rate of the regions as a function of their distance from the center for three of the galaxies in the sample. Overall, the star formation rate decreases from 1 billion years before the observation (red) to the time of observation (blue). However, the regions where the star formation decreases most significantly (indicated with the yellow boxes) vary from galaxy to galaxy. [Olsen et al. 2026]
It should be noted that all of the galaxies in this study are still forming stars. However, they are on the verge of having their star formation suppressed, offering valuable insight into how quenching begins and how diverse the process can be. New telescopes are pushing the boundaries of what we can observe. On one hand, JWST can capture galaxies at exceptionally high resolution; on the other, the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope will deliver vast datasets containing billions of galaxies. Future investigations leveraging these facilities could reveal more about the physical processes that quench galaxies on small scales, shedding light on the mechanisms that drive galaxy evolution.
Original astrobite edited by Catherine Slaughter.
About the author, Shalini Kurinchi-Vendhan:
After studying astrophysics and literature at Caltech, I moved onto a Fulbright Fellowship in Heidelberg, Germany. I’m passionate about using computer simulations to explore supermassive black holes and galaxy evolution — but I also love poetry and traveling.
The post Observing the End of Star Formation in Galaxies appeared first on AAS Nova.
The full view of the study region, showing the NIRCam and MIRI footprints. [Yoo et al. 2026]
“A JWST NIRCam/MIRI View of the W51A High-Mass Star-Forming Region,” Taehwa Yoo et al 2026 AJ 171 208. doi:10.3847/1538-3881/ae40b7
The post Featured Image: Massive Stars in the Making appeared first on AAS Nova.
Editor’s Note: For the remainder of 2025, we’ll be looking at a few selections that we haven’t yet discussed on AAS Nova from among the most-downloaded articles published in AAS journals this year. The usual posting schedule will resume January 2nd.
A team led by Zoie Telkamp (University of Virginia) used the Stratospheric Observatory for Infrared Astronomy, SOFIA, to study massive protostars and test theories of high-mass star formation. Contrary to the predictions of some star-formation models, the team found no evidence that massive protostars require a certain surface mass density to form. Formation in a cluster environment, however, may limit the formation of the most massive protostars.
Massive stars are rare, short-lived, and luminous. They influence their environments across a vast range of spatial and temporal scales, from advancing the epoch of reionization in the early universe to impacting the formation of individual planetary systems in the present-day universe. The fundamental question of how high-mass stars form is still unsettled. Theories of high-mass star formation range from scaled-up versions of low-mass star formation to scenarios involving collisions between protostars.
SOFIA FORCAST and Herschel Space Observatory images of protostars in the G18.67+0.03 star-forming region. Click to enlarge. [Telkamp et al. 2025]
Zoie Telkamp et al 2025 ApJ 986 15. doi:10.3847/1538-4357/adcd79
The post Selections from 2025: The Formation of Massive Stars appeared first on AAS Nova.
Editor’s Note: Shortly after the publication of this article, we became aware that the disk described in this work was previously discovered by Wei-Hao Wang, as reported in the Astronomer’s Telegram in July 2024.
On 23 June 2025, the public got its first look at images from the NSF–DOE Vera C. Rubin Observatory — and the discoveries are already starting to roll in.
A closeup of the Trifid Nebula from one of the Rubin Observatory first-look images. [Adapted from NSF–DOE Vera C. Rubin Observatory; CC BY 4.0]
The Trifid and Lagoon nebulae are both HII regions, making them ideal places to search for circumstellar and protoplanetary disks, as well as proplyds — protoplanetary disks that are in the process of being evaporated by the intense radiation from nearby massive stars. The glowing gas of an HII region provides the background illumination needed to pick out the silhouettes of dark and dusty disks.
The Trifid Nebula disk candidate identified in this work. [Adapted from Zamani & Rector 2025]
Published today in the Research Notes of the AAS, Mahdi Zamani (Zamani Scientific Visualizations & Imaging) and Travis Rector (University of Alaska Anchorage) reported the results of their search for proplyds in the Rubin image of the Trifid and Lagoon nebulae. The team detected one candidate circumstellar or protoplanetary disk on the edge of the Trifid Nebula, surrounded by tenuous, filamentary clouds of gas and dust.
The Rubin data don’t show evidence for ionized gas surrounding the disk, so it’s not yet clear if the object should be classified as a proplyd. The disk has a projected distance of 7.5 light-years from HD 164492A, the O-type star whose intense radiation is responsible for energizing the surrounding nebula, and may also be capable of ionizing the disk studied here.
The Orion molecular cloud complex is among the most active star-forming regions in the Milky Way, home to hundreds of protostars and thousands of pre-main-sequence stars. [ESO/H. Drass et al.; CC BY 4.0]
Researchers have searched the Trifid Nebula previously for signs of protoplanetary disks, but while those searches found evidence for disks around hot stars near the center of the cluster, this particular disk candidate went undetected. Previous searches likely didn’t cover a large enough area of the nebula, or perhaps lacked the resolution needed to differentiate between the dusty disk and the nearby filamentary gas clouds. With Rubin’s broad field of view and precise resolution, the observatory was well-positioned to spot this disk candidate.
“The Potential Discovery of a Circumstellar Disk in M20 from Rubin First Look,” Mahdi Zamani and T. A. Rector 2025 Res. Notes AAS 9 172. doi:10.3847/2515-5172/ade982
The post Astronomers Spot Possible Disk in Rubin Observatory First-Look Image appeared first on AAS Nova.
The glowing green nebula in this JWST image surrounds the star cluster IC 348, which is the subject of a recent study by Kevin Luhman (Penn State University) and Catarina Alves de Oliveira (European Space Agency). Using JWST’s Near-Infrared Camera, Luhman and Alves de Oliveira searched the cluster’s young stellar population for free-floating brown dwarfs — objects that are less massive than stars but more massive than most planets — and discovered multiple candidates with masses down to just twice the mass of Jupiter. Follow-up JWST spectroscopy confirmed the masses of these objects, making them the lowest-mass brown dwarfs known to date. In addition to their mass, these newly discovered brown dwarfs are remarkable because their spectra show evidence of hydrocarbon molecules, the exact identities of which are not yet known. Luhman and Alves de Oliveira proposed that low-mass brown dwarfs bearing this chemical signature be inducted into a new spectral class called “H” for “hydrocarbon.” To add to the intrigue of these objects, the authors also discovered signs of circumstellar disks around two of them, suggesting that they may be capable of forming and harboring planets. To learn more about the low-mass brown dwarfs in IC 348, be sure to check out the full research article linked below.
“A New Spectral Class of Brown Dwarfs at the Bottom of the IMF in IC 348,” K. L. Luhman and C. Alves de Oliveira 2025 ApJL 986 L14. doi:10.3847/2041-8213/addc55
The post Featured Image: Low-Mass Brown Dwarfs in a Class of Their Own? appeared first on AAS Nova.
JWST observations have begun uncovering some of the oldest star clusters in the universe, but their formation mechanisms are still uncertain. A recent study uses high-resolution simulations to understand early star formation and how local globular clusters may have originated.
Our leading cosmological model of the universe suggests that stars and galaxies coalesce within dark matter halos, eventually forming the larger structures we see today. However, some of the oldest astronomical objects in the universe — massive collections of stars called globular clusters — contain little to no dark matter, making their formation mechanisms somewhat mysterious. How do large clusters with thousands of stars form outside of dark matter halos?
Visualizations of the gas density in the simulated star-forming regions in this study. Click to enlarge. [Lake et al 2025]
Over the past decade, simulations and theory have shown that supersonically induced gas objects can form star clusters, which may be the origin story of many of the local globular clusters seen today. However, these simulations have been limited by their resolution. Unable to resolve individual star formation and not including key aspects like feedback, these simulations have left open questions about these dark-matter-free objects.
Seeking to more deeply understand supersonically induced gas objects, William Lake (University of California, Los Angeles; Dartmouth College) and collaborators perform high-resolution simulations that include detailed physics and can track the formation of individual stars. The simulations varied the metallicity and presence of protostellar jets, properties that are both known to impact the star formation process in gas clouds.
Mass distribution for the stars formed in the simulated supersonically induced gas objects. The simulated clusters form more high-mass stars than what is seen in local star-forming regions. Click to enlarge. [Lake et al 2025]
Given that these objects likely form very high-mass stars, these primordial star clusters will have extremely high stellar mass surface densities and brightnesses compared to what is observed locally. With such enhanced brightness, these objects may be bright enough for JWST to observe them. Further high-redshift observations of star clusters will allow for further constraints on the formation of the universe’s first stars and will yield more information about the possible origins of the globular clusters we see in the local universe.
“The Stellar Initial Mass Function of Early Dark Matter–Free Gas Objects,” William Lake et al 2025 ApJL 985 L6. doi:10.3847/2041-8213/add347
The post From Gas to Cluster: Simulating Star Formation in the Early Universe appeared first on AAS Nova.
A supermassive black hole 6 billion times the mass of the Sun lurks in MRG-M0138, a gravitationally lensed quiescent galaxy seen when the Universe was just 3 billion years old, according to an analysis of data collected by the NIRSpec Integral Field Spectrograph onboard the NASA/ESA/CSA James Webb Space Telescope.
The post Webb Weighs Most Distant Inactive Black Hole Ever Found appeared first on Sci.News: Breaking Science News.
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