Extragalactic Planetary Nebula with Massive Progenitor Sheds Light on Stellar Evolution

This Hubble Space Telescope image shows planetary nebula NGC 2022 glowing bright in visible light. The pink and purple rings are made up of material that was once the outer layers of the central star. Credit: ESA/Hubble & NASA, R. Wade; CC BY 4.0

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.

Open cluster AP 210 and planetary nebula M279 in the Andromeda Galaxy, as seen in archival Hubble observations.
Credit: Chen et al. 2026

Striking Gold

Numerous planetary nebula–open cluster pairs have been found in the Milky Way, but among those with well-constrained progenitor masses, very few push into the higher-mass regime where things get really interesting. Outside our home galaxy, the search has proven even more challenging due to data sparsity. Despite the odds, Pinjian Chen (Chinese Academy of Sciences) and collaborators have found a planetary nebula with one of the highest known progenitor masses in an open cluster in the Andromeda Galaxy.

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. Credit: 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.

By AAS Nova Staff

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

Source: American Astronomical Society/AAS-Nova

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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!

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NASA’s Webb Reveals Dynamic Panorama of Star Formation

IC 348 (NIRCam Image)

NASA’s James Webb Space Telescope recently observed IC 348, a star-forming region just 1,000 light-years away from Earth. Webb’s sharp vision revealed tiny brown dwarfs, some just twice Jupiter’s mass, and young stars ejecting powerful jets crashing into surrounding gas and dust.Credit Image: NASA, ESA, CSA, Kevin Luhman (PSU), Catarina Alves de Oliveira (ESA), Mahdi Zamani (ESA/Webb)

IC 348 Collage

This collage features a collection of insets from NASA’s James Webb Space Telescope’s image of star-forming region IC 348: embedded stars, a central star cluster, faint outflows, Herbig-Haro objects, gravitational lensing, and spiral galaxies. Credit Image: NASA, ESA, CSA, Kevin Luhman (PSU), Catarina Alves de Oliveira (ESA), Mahdi Zamani (ESA/Webb)

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This starry view of the nearby star-forming region IC 348 is one of the largest images released to date from NASA’s James Webb Space Telescope. Using Webb, astronomers searched IC 348 for brown dwarfs, which are less massive than the smallest stars. The researchers discovered brown dwarfs just twice the mass of Jupiter, bringing the study of these curious objects into a new mass range and revealing new insights about the star formation process.

The star-forming region IC 348 is located just 1,000 light-years away in the constellation Perseus. In regions like IC 348, cold clouds of molecular hydrogen gas collapse to form new stars, creating glowing, sculpted scenes like this one. The star-formation process can create widely varied objects, from massive stars that expire after only a few million years in core-collapse supernova explosions to the smallest and most common stars, which are long lived and produce powerful stellar storms.

The smallest stars weigh in at around 8 percent of the Sun’s mass. Below this mass lies a strange class of objects called brown dwarfs. Brown dwarfs form in the same way stars do, through the collapse of molecular clouds. However, unlike stars, the cores of brown dwarfs never become hot enough to fuse ordinary hydrogen into helium (though many briefly fuse deuterium, or heavy hydrogen, early in their lives).

What’s still not clear, and what researchers hoped to learn by using Webb’s sensitive instruments to study IC 348, is how small the smallest objects created by the star-formation process are. In other words, how small is the smallest brown dwarf?

Researchers seeking to answer this question first used Webb to study IC 348 in 2022, when they discovered brown dwarfs with masses as low as three to four times the mass of Jupiter. Now, the same research team has used Webb to probe even deeper into this region in search of even smaller brown dwarfs. The team used Webb’s NIRCam (Near-Infrared Camera) in 2024 to capture the warm glow of young brown dwarfs and newborn stars seen in this new image of IC 348. After selecting candidate brown dwarfs based on their colors and brightness, they followed up with Webb’s NIRSpec (Near-Infrared Spectrograph) in 2025 to conduct spectroscopic observations to study the masses of the brown dwarfs.

These deep Webb observations revealed something remarkable to the researchers: brown dwarfs with masses as low as just twice the mass of Jupiter or only 0.19 percent of the Sun’s mass — far smaller than theory predicts brown dwarfs should be. These are the least massive brown dwarfs known and their existence poses a challenge to models of how stars form.

In addition to the discovery of these unexpectedly lightweight brown dwarfs, the Webb observations contained even more surprises. One of the lightest newfound brown dwarfs showed signs of a disk, suggesting that small planets could be forming around an object that is itself only the mass of a planet.

While inspecting the spectra of IC 348’s brown dwarfs, the research team also found a feature they attributed to an unidentified hydrocarbon — molecules made only of hydrogen and carbon atoms. This specific feature has only been seen in the atmospheres of the lowest-mass brown dwarfs, suggesting that these extreme objects might exist in a spectral class of their own.

The stars and brown dwarfs of IC 348 aren’t the only attractions in this image. A brilliantly detailed collection of protostars occupies the upper right corner. Several of these protostars are accompanied by Herbig-Haro objects, which are luminous regions that form when jets from growing newborn stars crash into the gas and dust around the star.

The long, narrow feature that is oriented horizontally in this corner is the Herbig-Haro object HH 797. Upon close inspection, this source is revealed to be two protostars with nearly parallel outflows. Just to the right of HH 797 is the propeller-shaped source HH 211, which features both narrow jets and broader outflows.

The data used to create this image comes from the Webb General Observer Program 4866. In addition to studying the lowest-mass objects created through the star-formation process, this program also seeks to understand how the populations of planetary-mass objects like brown dwarfs vary between star-forming regions, as well as the origins of the hydrocarbon feature in the lowest-mass brown dwarfs.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

Source: NASA's James Webb Space Telescope/News

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Details:

Last Updated: Sep 15, 2026
Location: NASA Goddard Space Flight Center

Contact Media:

Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov

Bethany Downer
ESA/Webb
Baltimore, Maryland

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'Fingerprints' inside the Sun could reveal if it once swallowed a planet

An artist’s impression of a star engulfing a planet. The blue line traces the path of the planet as it spirals toward the star and ultimately collides with it. Credit: NASA, ESA, CSA, Ralf Crawford (STScI)

Licence type: Attribution (CC BY 4.0)

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It is thought the Sun may have engulfed a super-Earth-sized planet early in its history.

Now a new study has gone a step further by suggesting that such an event may have left behind detectable clues inside our star which could still be visible today.

This idea of a measurable signature or 'fingerprints' in the present-day solar interior was explored by research published today in Monthly Notices of the Royal Astronomical Society.

Professor Mutlu Yildiz, of Ege University in Turkey, said: "Our new study suggests that a planet several times more massive than Earth may have fallen into the young Sun and left a lasting chemical imprint deep inside it.

"By modelling the Sun's evolution and comparing the results with precise observations of its interior, we find that the ingestion of a super-Earth could help explain long-standing differences between standard solar models and observations, including subtle changes in the Sun's internal structure and its depleted lithium abundance."

Researchers also found that such a world could survive its passage through the Sun's outer layers while losing very little mass, which suggests that planets may leave detectable fingerprints inside their host stars long after they have disappeared.

For many years, solar models based on the standard physics of stellar evolution have had difficulty reproducing some helioseismic observations simultaneously, particularly the sound-speed structure just below the convection zone and the depth of the solar convection zone.

At the same time, the Sun shows a strong and well-known depletion of lithium at its surface.

"We were interested whether these problems might have a common origin in the early chemical history of the Sun," Professor Yildiz explained.

"Young stars are surrounded by protoplanetary discs, where substantial amounts of material can move between the disc and the star.

"Since planets are made of material that is chemically different from the gas in the disc, we wondered whether the early engulfment of a planet could have left a chemical signature inside the young Sun."

The researchers used the MESA stellar-evolution code to test their idea. They explored different accretion histories and compared the resulting solar models with helioseismic constraints and surface abundances, while also testing alternative explanations involving the equation of state, opacity, and different prescriptions for turbulent and convective mixing.

Their results favour a scenario in which the young Sun engulfed a super-Earth around 5–10 times the mass of Earth.

Importantly, their modelling also does not explain just one puzzle. It simultaneously matches several independent measurements of the Sun, including observations of its interior and its unusually low lithium abundance.

"We thought planetary engulfment might affect the solar structure but did not expect the calculations to converge on such a specific super-Earth mass range," said Professor Yildiz. "That was one of the most interesting outcomes of the study."

He added that while it may not be possible to definitively prove the Sun swallowed a planet, if the predicted structural and chemical signature could be independently identified through helioseismic or other observations, it would provide strong evidence for such an event happening billions of years ago.

Astronomers have long wondered why many other star systems appear to have large super-Earths, while ours has none.

The new study cites previous research from a decade ago by Martin & Livio (2016), which suggested that one or more super-Earths could have formed inside the orbit of Mercury and migrated inward through the gas disc, potentially falling into the young Sun.

However, although this research provided a theoretical pathway for an engulfment event, it did not require that such a planet was ultimately swallowed by our star.

"The earlier work proposed that a super-Earth could have formed and migrated into the young Sun. Our paper asks whether the Sun itself could still carry observable evidence that such an engulfment actually happened, and we believe it could," Professor Yildiz concluded.

"The next step is to see if these fingerprints can be independently detected."

Source: Royal Astronomical Society (RAS)/Research Highlights

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Media contacts:

Sam Tonkin
Royal Astronomical Society
Mob: +44 (0)7802 877 700
press@ras.ac.uk

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Science contacts:

Professor Mutlu Yildiz
Ege University
mutlu.yildiz@ege.edu.tr

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Images & captions

Swallowed by the Sun

Caption: An artist's impression of a star engulfing a planet. The blue line traces the path of the planet as it spirals toward the star and ultimately collides with it.

Credit: NASA, ESA, CSA, Ralf Crawford (STScI)

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Further information

The paper 'Planetary engulfment as a solution to solar-model discrepancies and its implications for planetary systems' by M. Yildiz has been published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/stag1527.

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Notes for editors

About the Royal Astronomical Society

The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

The RAS organises scientific meetings, publishes international research journals, recognises outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internation which experts on the Editorial Boards accept the papers for publication. The Society issues press releases based on a similar principle, but the organisations and scientists concerned have overall responsibility for their content.

Keep up with the RAS on Instagram,Bluesky,LinkedIn,Facebook and YouTube.

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Submitted by Sam Tonkin on Thu, 10/09/2026 - 08:30

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New study reveals common pattern of black hole activity shaping nearby galaxies

Image of galaxy NGC 1386, taken with Legacy Surveys
DR10

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Observations of nine nearby galaxies show how active supermassive black holes influence star formation and shock waves across their host galaxies.

Cambridge, MA (September 14, 2026) —A new study of nine nearby galaxies has shown that actively growing supermassive black holes may contribute to star formation, instead preventing star formation, in their host galaxies.

The research, based on observations from the VLT/MUSE instrument, shows that active galactic nuclei (AGN), or bright regions powered by material falling into a supermassive black hole, are associated with star-forming rings or arcs, cone-shaped regions of energized gas, and fast “shocks,” which occur when energy outflows interact with surrounding gas.

The findings, published today in The Astrophysical Journal, give a new perspective on how AGN feedback could influence the growth and evolution of galaxies.

“Once we resolved them, we could see that they not only accrete things, but they also eject things,” said Peixin Zhu, graduate student and astronomer at the Center for Astrophysics. “The injection and accretion are linked with each other.”

The study focused on galaxies whose central black holes are actively accreting, or pulling in, nearby material.

“We’re seeing that black holes are not just consuming material at the centers of galaxies, but they’re actively reshaping their surroundings,” said Lisa Kewley, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian, director of the Center, and Zhu’s advisor. “This work helps us understand a complex feedback cycle that plays an important role in galaxy evolution.”

The team used a new three-dimensional diagnostic technique to distinguish among three sources: star formation, radiation from the active black hole and excitation by shocks. Shock excitation occurs when high-speed outflows from the central black hole collide with the interstellar medium.

The galaxy NGC 1386, shown in grayscale on the left and zoomed in to the central region on the right. The colors represent star formation in red, black-hole radiation in blue, and shocks in yellow. Image courtesy Peixin Zhu.

Across the sample, the researchers found that star-forming rings or arcs appeared at distances of about 0.8 to 6 kiloparsecs from the galactic center. Ionized cones of black-hole radiation extended outward from the galaxies’ discs, while central regions dominated by fast shocks often extended perpendicular to those bicones.

The researchers also found evidence for shocks in directions perpendicular to the AGN bicones. Zhu notes that these shocks are broadly consistent with interactions between AGN jets and the interstellar medium, although winds from the active black hole may also contribute, particularly in galaxies with lower-power jets.

“The most interesting phenomena about shocks is that they always go perpendicular to where the black hole’s injected outflows go,” Peixin said. “It is very common, and we see it consistently appearing across the whole nine galaxies.”

The study’s results combined high-resolution observations and detailed theoretical models. The MUSE instrument provided spatially-resolved optical data, while the state-of-the-art theoretical models built by Zhu and her colleagues, astrophysicists Lisa Kewley of the Center for Astrophysics and Ralph Sutherland of the Australian National University, allowed them to compare observations with predictions for black hole activity, star formation and shocks. Chandra X-ray observations also independently supported the researchers’ interpretation.

The results demonstrate that actively growing black holes have a complex cycle of accretion, outflow and interaction with their surrounding galaxies. By separating the effects of black hole radiation, star formation and shocks, the study provides a clearer view of that cycle and its relationship to star formation.

Source: Harvard-Smithsonian Center for Astrophysics (CfA)/News

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About the Center for Astrophysics | Harvard & Smithsonian

The Center for Astrophysics | Harvard & Smithsonian is a collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory designed to ask, and ultimately answer, humanity’s greatest unresolved questions about the universe.

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NASA's Chandra Unveils Mysterious X-ray Objects

Fast Facts for M101 The Pinwheel Galaxy)
Credit: X-ray: NASA/CXC/Univ. of Alabama/M. Muhibullah et al.; Optical: NASA/ESA/STScI;
Image Processing: NASA/CXC/SAO/N. Wolk

JPEG (713.5 kb) - Large JPEG (61.4 MB) - Tiff (352.8 MB) - More Images

A Tour of NASA's Chandra Unveils Mysterious X-ray Objects - More Videos

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• Astronomers found a new class of objects using NASA’s Chandra X-ray Observatory.


• They dubbed these “hypersoft X-ray sources” (HSS) because they give off very low-energy X-rays that are difficult to detect.


• Despite their stealth output, HSS may be emitting large amounts of ultraviolet radiation.


• This discovery may help scientists unravel mysteries around Type Ia supernovas and the intergalactic medium.

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Astronomers have discovered a new class of objects in multiple galaxies. This result, made possible by NASA’s Chandra X-ray Observatory and outlined in our latest press release, may help scientists solve two outstanding mysteries in astrophysics.

The face-on spiral galaxy M101, also known as the Pinwheel, is one of the galaxies where the new type of object was found. This new M101 composite image contains X-ray data from Chandra (purple) that have been combined with an optical image from the Hubble Space Telescope (red, green, and blue). Circles in an annotated version of the image show the location of the seven newly-discovered objects in M101.

M101 with illustrated circles calling out seven of the newly-discovered objects. (Labeked)
Credit: X-ray: NASA/CXC/Univ. of Alabama/M. Muhibullah et al.; Optical: NASA/ESA/STScI;
Image Processing: NASA/CXC/SAO/N. Wolk

Researchers found a total of 84 of these mysterious objects in M101, Messier 31, and four elliptical galaxies. The objects were named “hypersoft X-ray sources” because they give off very low-energy X-rays that Chandra was only able to detect after long exposures. Because low-energy X-rays border energetic ultraviolet radiation on the electromagnetic spectrum, the team determined that these sources are likely producing large amounts of energetic ultraviolet radiation.

Astronomers are trying to determine what type — or types — of objects are responsible for these low-energy X-rays and intense ultraviolet radiation outputs. The most likely explanation, according to the team, is that these systems involve a black hole, neutron star or white dwarf pulling material from a companion star. The material pulled from the companion star is heated up to produce X-rays before falling onto the white dwarf or neutron star, or into the black hole. While scientists have discovered many binary systems over the years, astronomers have never seen any behaving like this before.

The discovery of this new class of sources suggests that astronomers have missed large populations of binary systems with energetic ultraviolet radiation until now. One idea is that these binary systems are the precursors to Type Ia supernova explosions, which astronomers used to discover the acceleration of the universe’s expansion.

Another open question that these hypersoft X-ray sources could help answer involves the stripping of electrons from gas in between galaxies. Scientists know this phenomenon plays an important role in the lifecycle of the stars, but they still need to accurately account for all of the energy sources that contribute to this process. This newly-discovered class of objects may play a significant role in this stripping.

These hypersoft X-ray sources were not found until now because in addition to the low-energy X-ray output that requires large amounts of observing time from a telescope like Chandra, the high-energy ultraviolet radiation is readily absorbed by helium and hydrogen gas that fills the space in between the stars. This creates a “nearly impenetrable barrier” to look through.

A paper describing this result appears in the most recent issue of Nature Astronomy and is available here. The authors of this paper are Mustafa Muhibullah (University of Alabama), Jimmy Irwin (University of Alabama), and Rosanne DiStefano (Center for Astrophysics | Harvard & Smithsonian).

NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.

Quick Look: NASA's Chandra Unveils Mysterious X-ray Objects

Source: NASA’s Chandra X-ray Observatory

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Fast Facts for M101, The Pinwheel Galaxy

Credit: X-ray: NASA/CXC/Univ. of Alabama/M. Muhibullah et al.; Optical: NASA/ESA/STScI; Image Processing: NASA/CXC/SAO/N. Wolk

Release Date: September 9, 2026
Scale: Image is about 14 arcmin (86,000 light-years) across.
Category: Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 14h 03m 12.5s | Dec +54° 20´ 56.2"
Constellation: Ursa Major
Observation Dates: 25 observations from March 2000 to January 2005
Observation Time: 274 hours (11 days 10 hours)
Obs. ID: 934, 3095, 4731-4737, 5296, 5297, 5300, 5309, 5322, 5323, 5337-5340, 6114, 6115, 6118, 6152, 6169, 6170, 6175
Instrument: ACIS
Also Known As: NGC 5457, The Pinwheel Galaxy
References: Muhibullah, M., Irwin, J.A., and Di Stefano, R., 2026, Nature Astronomy (available here)
Color Code: X-ray: purple; Optical: red, green, and blue
Distance Estimate: About 21 million light-years from Earth

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NuSTAR as a fast X-ray transient detector

This artist’s illustration shows a high-speed jet of material being launched from a gamma-ray burst source embedded in a very dusty galaxy—the sort of powerful explosion that may cause high-energy fast X-ray transients. Image credit: NOIRLab/NSF/AURA/M. Garlick. Download Image

On August 28th, NuSTAR detected a fast X-ray transient (FXT) in the field of view of an observation of a distant quasar. FXTs are flashes of X-rays that last for seconds to hours that may be related to Gamma-ray bursts and the collapse of massive stars. FXTs were first serendipitously found in Chandra observations, and the field is currently being revolutionized by the Einstein Probe. Recently, staff scientist Murray Brightman, a member of the NuSTAR Science Operations Center, implemented a program to search for these transients in NuSTAR data in near real time, soon after the data are downloaded and processed at the SOC. Since NuSTAR detects higher energy X-rays than Chandra or Einstein Probe, FXTs detected by NuSTAR may be a distinctly different type of source than FXTs detected by lower-energy instruments. Finding these sources in real time allows for follow-up with other telescopes. Murray alerted the community about the event on August 28th, named NuSTAR 260828, by submitting a GCN (https://gcn.nasa.gov/circulars/45478). Two teams followed up the event by observing with optical telescopes to search for a counterpart (https://gcn.nasa.gov/circulars/45488 and https://gcn.nasa.gov/circulars/45507). None has been found so far, but the search continues.

Source: NASA's Nuclear Spectroscopic Telescope Array (NuSTAR)/Weekly Highlights

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Fast Radio Bursts Poised to Help with Biggest Cosmic Mysteries

This illustration shows a fast radio burst (FRB) arriving at a radio telescope array on Earth. The FRB originates during an energetic event in a distant galaxy, but as it passes through intervening clouds of gas, a process known as optical refraction spreads the colors of the burst out much like a prism turns sunlight into a rainbow. This causes the shorter, bluer wavelengths to arrive before the longer, redder wavelengths. This illustration was made by artists in collaboration with researchers to ensure technical accuracy. Credit: Caltech/Robert Hurt & Keith Miller (IPAC - SELab)

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The future Deep Synoptic Array will catch tens of thousands of FRBs, enhancing the power of this cosmology tool

Intense, brief flashes of radio light called fast radio bursts (FRBs) travel across billions of light-years to reach Earth, passing through a fog of matter along the way. The bursts' origins are unclear but are thought to possibly come from highly magnetized dead stars called magnetars. The denser the fog the FRBs travel through, the more their signals will become dispersed—similar to the way a prism splits white light into a rainbow of colors.

Thanks to this dispersing trait, FRBs make excellent tracers of how ordinary matter is distributed in the universe; ordinary matter is the same stuff that makes up people, planets, stars, and anything made of subatomic particles called baryons. As the FRB radio beams pass through this matter in our universe, they can essentially map out how much is present and how clumpy it is.

Using Fast Radio Burstos to Map Matter in the Universe

Professor of Astronomy Vikram Ravi talks about fast radio bursts, or FRBs, and how these intense flashes of radio waves can be used to map out the distribution of ordinary matter in our universe.

The new study, which analyzed a sample of about 100 FRBs, is the first to directly measure the impact of feedback on clumpy matter in the large-scale regions around and between galaxies. The results show that galactic feedback does indeed smooth surrounding material, making it less clumpy. However, it does so less than what has been measured previously by state-of-the-art surveys, including the eROSITA X-ray telescope, and the former microwave-based Atacama Cosmology Telescope in Chile, which ended in 2022.

"Our analysis of FRBs reveals how gas ejected by astrophysical feedback suppresses cosmic structure, delivering constraints competitive with X-ray and microwave surveys," says coauthor Elisabeth Krause (PhD '12), a professor of astronomy and physics at The University of Arizona. "This is amazing considering we only had about 100 FRBs in our sample. It's only the beginning."

Caltech's Deep Synoptic Array (DSA), a powerful radio telescope scheduled to be built by 2029 in a remote valley in Nevada, is expected to find tens of thousands of FRBs, vastly enhancing the cosmic events' power to improve cosmology measurements. Data from the DSA, which is funded by Schmidt Sciences, will work synergistically with several cosmology experiments, including the European Euclid mission, in which NASA's Jet Propulsion Laboratory and Caltech's IPAC astronomy center play key roles (Caltech manages JPL for NASA); the Dark Energy Spectroscopic Instrument (DESI) in Arizona; the Vera Rubin Observatory in Chile; and NASA's newly launched Nancy Grace Roman Telescope, in which JPL and Caltech's IPAC also play roles.

"The DSA will be a game changer for the field," says Ravi, who is the co-principal investigator on the DSA project.

The Nature Astronomy paper is titled "Signatures of Suppressed Matter Clustering revealed by Fast Radio Bursts." This work builds on a series of related studies from the team, including "Baryons in the Darkest Sites of the Universe," "Backlighting the Cosmic Web with Fast Radio Bursts: An Anthology of Dispersion Measure Cross-Correlations with Large-Scale Structure and Baryon Tracers," "Quantifying the Impact of Selection Effects on FRB DM–z Relation Cosmological Inference," "Probing Baryonic Feedback and Cosmology with the 3×2-point Statistic of FRBs and Galaxies," and "A Hydrodynamical Simulations-based Model that Connects the FRB DM-Redshift Relation to Suppression of the Matter Power Spectrum via Feedback."

Fast Radio Burst (FRB) Dispersion

This animation shows how the signals from fast radio bursts (FRBs) become dispersed as they travel through clouds of gas around and between galaxies. Animation credit: Caltech/Robert Hurt (IPAC - SELab)

In a new Nature Astronomy study, researchers show how these FRB measurements can help to solve some of the biggest questions in cosmology.

"We've established that FRBs are a leading probe of the distribution of matter in the universe," says Kritti Sharma (MS '24), lead author of the new study and a graduate student working with Vikram Ravi, a professor of astronomy at Caltech and a coauthor of the paper. "These FRB data can be used to enhance cosmology experiments that are trying to answer questions about dark matter, dark energy, and the mass of neutrinos."

Many questions persist about the nature of dark energy, a repulsive force or substance that is causing our universe to fly apart at increasing speeds, and about dark matter, a substance that far outweighs matter in our universe but cannot be seen. Mysteries about neutrinos, ghostly particles that pass freely through ordinary matter, also endure—including the particles' mass, a measurement that could help reveal how large-scale galactic structures in the universe formed.

Dark energy, dark matter, and neutrinos are all predicted to influence how matter clumps together, so scientists use sky surveys to map this clumping and gain clues to the nature of these cosmological phenomena. The problem is that feedback processes inside galaxies can also affect how smooth or clumpy matter is, muddying the researchers' ability to precisely measure the cosmological effects.

All galaxies harbor supermassive black holes at the centers, which voraciously feed on nearby matter while also ejecting winds of hot, ionized—or charged—gas into their surroundings. Exploding stars can also expel energy into the galactic neighborhoods. This feedback has a role in smoothing out the material outside the galaxies, making it less clumpy.

"The feedback process thins the gas around the galaxies, redistributing matter across vast distances. It smooths out clumps of matter in a way that looks astonishingly similar to what massive neutrinos do, or what dark energy or dark matter theories predict," Ravi says. "Unless scientists can independently measure this contribution from feedback, they can't tell these effects apart."

Coauthors on the study include Pranjal R. S. (University of Arizona); Dhayaa Anbajagane (University of Chicago); and Liam Connor (Harvard and Smithsonian Center for Astrophysics). Coauthors on related studies include Assistant Professor Kimmy Wu and staff scientist Casey Law (Caltech); Simone Ferraro (UC Berkeley); Sebastian Grandis (University of Innsbruck); David Alonso and William Coulton (University of Oxford); Yi-Kuan Chiang (Academia Sinica Institute of Astronomy and Astrophysics); Samuel McCarty (Harvard and Smithsonian Center for Astrophysics); Nico Schuster (Aix-Marseille University); Alice Pisani (Princeton University); Shivam Pandey (University of Arizona); Nico Hamaus (University Observatory Munich); and Robert Reischke (University of Bonn).

This research was supported by Schmidt Sciences; the National Science Foundation; the Kavli Institute for Theoretical Physics; the David and Lucile Packard Foundation; the European Research Council; Aix-Marseille University's French Initiative of Excellence; the Austrian Research Promotion Agency; Austria's Federal Ministry of Innovation, Mobility, and Infrastructure; and the Austrian Space Applications Program.; and the Austrian Space Applications Program.

Written by Whitney Clavin

Source: Caltech/News

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Contact:

Whitney Clavin
(626) 395‑1944
Email: wclavin@caltech.edu

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Authors:

Kritti Sharma (Lead author and a graduate student)

Vikram Ravi (Professor of Astronomy at Caltech and a Coauthor of the paper)

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Black holes outgrow their galaxies

This is how researchers envision the center of an active galaxy, where matter swirls around a supermassive black hole before falling into its center of mass. In the process, the incoming matter heats up to such an extent that, when viewed from Earth, it is primarily the brightly glowing core that is visible. © Animation: Johannes Buchner (MPE), 3D visualisation: Angel Ruiz, Maria Chira, Antonis Georgakakis (NOA, 4MOVE-U)

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To the Point:

• Black Holes and Galaxies: Eight black holes that were studied are extremely massive compared to their host galaxies and grew disproportional to the galaxies themselves.


• Unusual Mass Ratios: The ratio of black hole mass to stellar mass in the galaxies is at least 1 to 20, which is significantly higher than the typical value of about 1 to 200.


• Black Hole Growth Phase: The black holes are currently accreting matter at a rate that could double their mass within about one billion years.


• Future Research: Additional eROSITA data and high-resolution observations will help determine how common these systems are and how the host galaxies evolve.

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eROSITA identifies active black holes with unusually high mass fractions

An international team of astronomers has identified eight active black holes whose masses account for at least five per cent of the total stellar mass of their host galaxies. In the nearby Universe, the corresponding fraction is typically about half a per cent. The result challenges the widely held view that galaxies and the black holes at their centres always grow in close step.

The study, led by the Max Planck Institute for Extraterrestrial Physics (MPE), is based primarily on data from the eROSITA X-ray telescope and observations at ultraviolet, optical and infrared wavelengths.

The team searched a 140-square-degree region of the sky containing 22,079 quasars. Quasars are active galactic nuclei in which matter falls towards a supermassive black hole and releases large amounts of radiation. The intense X-ray emission detected by eROSITA reveals that the black holes in the eight selected systems are actively accreting matter.

“Astronomers assumed that central black holes always grow closely coupled to their host galaxies. Our results show that this is not always the case,” says Johannes Buchner, Postdoc at MPE, who led the study with international collaborators.

An extreme mass ratio

In the eight systems, the mass ratio between the black hole and the total stellar mass of the host galaxy is at least about 1:20. The black hole therefore accounts for at least roughly five per cent of the host galaxy’s stellar mass – more than ten times the typical value in the nearby Universe.

For a statistically well-defined subsample, the researchers also examined the 200 brightest quasars in a particularly deep part of the survey field. Three of the eight extreme objects were among the 200 brightest quasars in the survey. Simulations that account for the selection procedure and measurement uncertainties indicate that the systems are not simply isolated outliers, but represent a distinct population at the extreme end of the distribution.

The black holes have masses between approximately 800 million and four billion solar masses. They are therefore roughly a thousand times more massive than Sagittarius A*, the black hole at the centre of the Milky Way.

"Think of it like finding a Great Dane living in a studio apartment. The black hole has simply grown too large for its home.", says Prof. Kirpal Nandra.

Measuring the black holes

The researchers estimated the black-hole masses from optical spectra obtained by the Sloan Digital Sky Survey. The analysis relied in particular on the broad H-beta emission line, produced by ionised gas moving in the vicinity of the black hole.

The width of the line provides information about velocity, indicating that gas is circling the black hole with 40,000,000 km/h. Combined with an estimate of its luminosity, this allowed doctoral students Catarina Aydar and Qiaoya Wu to infer the black-hole mass. The method is calibrated for the mass range and cosmic epoch covered by the study. The uncertainty for individual black-hole masses is nevertheless approximately a factor of three. The conclusion therefore rests not on the exact mass of any one object, but on the statistical evidence for the population as a whole.

“The spectra reveal black holes with masses of roughly one to four billion Suns. What is particularly unusual, however, is their mass relative to the stellar mass of their host galaxies,” says Qiaoya Wu, a doctoral researcher at the University of Illinois Urbana-Champaign.

Animation of a black hole in a galaxy, growing in mass as matter falls in, glowing bright as a quasar. The growth of the black hole causes the mass ratio between black hole and stars to change, finally becoming "overmassive", like the found objects. Download video

Faint host galaxies

The black holes are clearly detected as active quasars through their X-ray emission. Their host galaxies, by contrast, are very faint or not unambiguously detected in the available images.

The team analysed observations across several wavelength ranges, including ultraviolet data from the GALEX satellite, optical images from the DESI Legacy Imaging Survey, near-infrared data from the VISTA Hemisphere Survey and infrared observations from the WISE satellite. The researchers modelled the quasar and galaxy light separately.

If the host galaxies had stellar masses comparable to that of the Milky Way, they would be substantially brighter in the available images. The observations therefore indicate that the galaxies contain considerably fewer stars. They do not yet establish whether the galaxies are small, compact or largely inactive, nor whether they are still forming stars.

“The faintness of the host galaxies shows that they cannot contain a stellar population comparable to that of a Milky-Way-sized galaxy. If they did, they would be much more clearly visible,” says Johannes Buchner.

Higher-resolution observations will be needed to determine the morphology and stellar populations of the host galaxies.

The black holes are still growing

The X-ray emission shows that the black holes are currently accreting matter. The team estimates an average growth rate of approximately 40 million solar masses per billion years. At that rate, their masses could double on a timescale of roughly one billion years.

If accretion continues, the mass ratio between the black hole and the stellar component of the host galaxy will become even more extreme.

“These black holes are already unusually massive compared with their host galaxies, yet they are still growing,” says Catarina Aydar, a doctoral researcher at MPE.

Results of measurements of stellar mass (from ultraviolet to infrared images) and black hole mass (from spectra). Optical galaxy image cutouts are positioned at the measured values. Most galaxies lie close to the orange line, with a mass ratio of 0.5%. The largest ratios of black hole to stellar mass are found in the upper left, above the dashed line marking 5%. Left-pointing triangles indicate cases where only an upper limit on the stellar mass could be determined, meaning the true ratio could be much higher than 5%. © Buchner et al., 2026

A challenge for galaxy-evolution models.

The observations point to a possible growth channel in which black holes temporarily gain mass faster than the stellar populations of their host galaxies. Current cosmological simulations do not produce systems with such extreme mass ratios.

The researchers compared their results to the Illustris, TNG, Horizon-AGN, EAGLE, Simba, Magneticum and ASTRID computer simulations. These models predominantly produce stellar to black hole mass ratios near the local value of 1 to 200. Systems as extreme as the ones observed are not produced.

The results therefore expose a limitation in existing models of the co-evolution of galaxies and their central black holes. They also provide a possible link to the overmassive black holes observed in the early Universe, where similarly extreme systems have raised questions about how rapidly black holes can grow. An important open question is: How could the black hole grow to be so massive, without the galaxy forming stars proportionally?

“These results are exciting and unexpected. We had assumed that galaxies and their central black holes grow closely connected to one another. These observations indicate that black holes can become extremely massive relative to their galaxies, apparently to a large extent independently of the evolution of the stellar population. This challenges us to rethink how black holes grow over cosmic history,” says Roberto Maiolino, a professor at the University of Cambridge, who was not involved in the study.

The eight quasars are likely to represent only the active, observable part of a larger population. Inactive or heavily obscured black holes cannot be identified as easily using the method applied here. Further eROSITA data and spectroscopic surveys will help determine how common these systems are.

The key open question is how the black holes gained so much mass without a corresponding increase in the stellar mass of their host galaxies. High-resolution observations will show whether the galaxies are still forming stars, how they are structured and how gas reached their central black holes over extended periods.

Source: Max Planck Institute for Extraterrestrial Physics/News

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Contacts:

Dr. Johannes Buchner
Postdoc High-Energy Astrophysics
Tel: +49 89 30000-3558
Email: jbuchner@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

Prof. Dr. Kirpal Nandra
Director of the High-Energy Astrophysics
Tel: +49 89 30000-3401
Email: knandra@mpe.mpg.de
Max-P.lanck-Institut für extraterrestrische Physik, Garching

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Original Publication

Buchn.er, J., I. Gauger, Q. Wu et al.
A lar,brge population of overmassive black hole quasars at z=0.3-0.8 revealed by eROSITA
A&A

Source | DOI

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Further Information

eROSITA delivers the most comprehensive census of the high-energy Universe to date

July 31, 2026
Second data release nearly doubles the previously known eROSITA X-ray sources to two million

An appetizer to the all-sky banquet

June 28, 2021
First eROSITA X-ray data release to the public

The X-ray sky opens to the world

With about 900 000 distinct sources, the first eROSITA All-Sky Survey (eRASS1) has yielded the largest X-ray catalogue ever published. Based on just the first six months of observations, eROSITA has already detected more sources than had previously been known in the 60-year history of X-ray astronomy.

Baryons at the Edge: SRG/eROSITA Survey Detects “Missing” Cosmic Gas at the Outskirts of Galaxy Clusters

May 05, 2026
Missing baryons found in galaxy cluster outskirts.
Research uncovers 90% of missing baryonic matter in galaxy cluster outskirts, enhancing cosmic structure understanding.

eROSITA sees changes in the most powerful quasar

May 19, 2023

Researchers have observed the X-ray emission of the most luminous quasar seen in the last 9 billion years of cosmic history. Significant changes in the quasar’s emission give a new perspective on the inner workings of quasars and how they interact with their environment.

Space Telescope Studies Solar System X-ray Glow

April 16, 2026
SRG/eROSITA reveals how our Solar System modifies the appearance of the X-ray sky

eROSITA witnesses the awakening of massive black holes

April 29, 2021

Using the SRG/eROSITA all-sky survey data, scientists at the MPE have found two previously quiescent galaxies that now show quasi-periodic eruptions.

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ALMA Watches a Massive Binary Assemble in Real Time

T 

The inset circle shows an ALMA 0.9 mm continuum image of the central binary system of IRAS 07299−1651 with the reconstructed orbital trajectories overlaid. The red- and blue-shifted hydrogen recombination line emission traces the rotation of the ionized circumstellar disks around the two forming stars, while the arrows indicate the directions of the bipolar jets. Background: Mid-infrared image of the region obtained with JWST (red = F470N, green = F405N, blue = F360M). Credit: NASA, ESA, CSA, STScI, J. DePasquale (STScI), ALMA (ESO/NAOJ/NRAO), Y. Zhang

 

An artist’s impression of the formation of a close massive binary system, showing misaligned disks around two young stars.
Credit: Y. Zhangdiv

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Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have captured one of the most detailed three-dimensional views yet of a massive binary star system while it is still being born. By tracking the motions of two young, massive stars over nearly eight years, the team found that the pair follows a highly stretched-out orbit and is surrounded by strongly tilted gas disks, both relative to each other and to the stars' orbit. The findings suggest the two stars didn't form together from a single spinning disk of material, as is often assumed, but instead formed independently and later came together in a close gravitational encounter, revealing a new way close massive binary star systems may form.

Most massive stars are born with stellar companions, and at least 90% are thought to exist in binary or higher-order multiple systems. These massive binaries go on to shape their surroundings dramatically, through supernova explosions and the production of heavy elements. But because most known massive binaries are only studied long after they've finished forming, astronomers have had few opportunities to catch the actual moment of assembly.

An international team led by Yichen Zhang of Shanghai Jiao Tong University set out to change that by studying IRAS 07299−1651, a system containing two massive protostars, stars still growing by pulling in surrounding gas and dust. The team had studied this system before, in 2019, when ALMA observations first provided direct dynamical constraints on the pair. At the time, the results seemed broadly consistent with the standard picture: two stars forming together from the fragmentation of one large disk. But one detail didn't quite fit: the disks around the two stars already looked oddly misaligned.

To dig deeper, the researchers spent nearly eight years measuring extremely subtle shifts in the two stars' positions on the sky, a technique that requires exceptional precision and is well within ALMA's capabilities. "For the first time, we were able to watch two massive stars move around one another while they were still being born," said Yichen Zhang, corresponding author of the study.

The team combined this long-term ALMA monitoring with data from the U.S. National Science Foundation's Very Large Array (VLA), as well as infrared images from the James Webb Space Telescope (JWST) and ESO's Very Large Telescope (VLT), which traced jets of material streaming away from the young stars. Together, these observations let the team reconstruct, for the first time, the system's full three-dimensional architecture, how the stars orbit each other, how their disks are tilted, and how their jets point into space.

"Each telescope revealed a different piece of the puzzle," said Rubén Fedriani, a co-author of the study. "The combination of radio and infrared observations provides the most exquisite detail on the formation of this massive protobinary system."

What they found surprised them. Instead of a neat, roughly circular orbit, the stars are following a highly eccentric trajectory, with the preferred orbital solutions lying close to a parabolic path. And rather than being aligned, as would be expected if the stars formed from the same disk, their surrounding disks are tilted at a sharp angle to each other and to the orbit itself. "It felt like solving a three-dimensional puzzle," said Yao Wang, the study's first author. "Each new observation added another piece, and eventually the orbit, disks, and jets all came together into a single, coherent picture."

This mismatched, chaotic-looking architecture is hard to explain if the two stars grew up together in the same disk — in that scenario, they'd be expected to inherit similar, well-aligned spins. Instead, the evidence points to a different origin story: the two stars likely began forming separately, in their own individual pockets of gas, before a chance close encounter brought them into their present configuration while they were still wrapped in their birth cloud. In representative orbital solutions, the stars passed closest to each other only about 60 years before the observations, practically an instant on cosmic timescales. The compact disks seen today appear to have survived the encounter, retaining well-defined rotational structures.

"This study demonstrates that the early lives of stars can be quite chaotic, with a chance encounter leading to this gravitational dance and stellar coupling," said Jonathan C. Tan, a co-author of the study. It's still not certain whether the two stars will stay gravitationally bound to each other for good — their current motion sits close to the dividing line between a bound orbit and one that could eventually fly apart, and interactions with the surrounding gas may still nudge their fate one way or the other. Future observations will help pin that down.

More broadly, the study opens a new way of investigating how massive binary stars come together. By applying the same long-term monitoring approach to other young massive binaries, astronomers hope to learn how often close encounters like this one—rather than shared birth in a single disk—build the massive binary systems seen across our galaxy.

Source: ALMA (Atacama Large Millimeter/submillimeter Array)/Press Releases

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Additional Information

The results of this research appear in Nature Astronomy as "An eccentric massive protobinary assembled via a core-merger parabolic encounter" by Y. Wang et al.

This article is based on the original press release by the National Astronomical Observatory of Japan (NAOJ), an ALMA partner on behalf of East Asia.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF), and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan, and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning, and operation of ALMA.

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Contacts:

Nicolás Lira
Education and Public Outreach Officer
Joint ALMA Observatory, Santiago - Chile
Phone: +56 2 2467 6519
Cel: +56 9 9445 7726
Email: nicolas.lira@alma.cl

Seiichiro Naito
NAOJ EPO Lead
Email: naito.seiichiro@nao.ac.jp

Jill Malusky
Public Information Officer
NRAO
Email: jmalusky@nrao.edu

Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Phone: +49 89 3200 6670
Email: press@eso.org

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NASA’s Hubble, Webb Find Far-out Solar System Objects ‘Remember’ Past

Trans-Neptunian Object Illustration

This artist’s concept depicts a Trans-Neptunian Object, a small, faint, icy body orbiting the Sun beyond the orbit of Neptune. These objects are so small that even with NASA’s Hubble and Webb space telescopes, they appear only as tiny points of light. Credit Artwork: NASA, ESA, Leah Hustak (STScI)

Tiny Worlds Discovered by Hubble and Webb

This video explains how Hubble and Webb are giving scientists a new look at some of the solar system’s oldest survivors and revealing new clues about how the building blocks of planets, including Earth, first formed. Credit: NASA's Goddard Space Flight Center.

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For the first time, scientists used the joint power of NASA’s Hubble and James Webb Space Telescopes to study some of the most far-flung bodies in our solar system, Trans-Neptunian Objects (TNOs). Some of these are the smallest and faintest ever directly seen. The researchers unexpectedly found fewer small TNOs than they expected, and that the colors of these bodies followed the same relationships as their larger family members

. These objects are typically small, faint, icy bodies orbiting the Sun beyond the orbit of Neptune. Most are more than 100 million times dimmer than objects visible to the unaided eye. In two complementary papers published Tuesday in The Astronomical Journal, teams analyzed the color, composition, and size distribution of 27 newly discovered tiny, dim TNOs.

This class of small bodies offers the best view into an early stage of planet-building, when a disk of dust and pebbles in orbit around the Sun coalesced into city-sized “planetesimals” — the solid building blocks that clump together to form planets — but had not yet merged into full-sized worlds. Beyond Neptune, this second stage never happened, leaving behind a frozen population of planetesimals.

In the deepest TNO survey to date, teams led by PhD candidates from the University of Victoria in Canada, under the guidance of the National Research Council of Canada, and Northern Arizona University in Flagstaff examined a patch of sky simultaneously with Hubble, observing the TNOs’ visible light, and Webb, observing their infrared light. The team of researchers measured the objects' colors, which are like a fingerprint of the surface composition, as well as their sizes and determined their orbits.

In the coordinated observations, the teams studied two different types of TNOs. The first, dynamically “cold” TNOs, are on their original, relatively circular orbits around the Sun in the plane of the solar system. The second type, dynamically “hot” TNOs, formed between the current locations of Uranus and Neptune but were pushed outward where they are today when the outer gas giants migrated early in the solar system’s history. Today they reside in highly elliptical orbits and move in and out of the plane of our solar system.

Prior to these observations, astronomers thought that small TNOs from both hot and cold populations would have undergone many collisions, changing their surfaces compared to larger TNOs. But that's not what the observations showed. Instead, the small bodies look like their larger counterparts. This implies that collisions are not changing the surfaces significantly—perhaps because there are fewer collisions than expected, or because the TNOs somehow retain their primordial, pre-collision compositions. The teams are still trying to unravel this mystery.

“You could imagine a scenario where getting knocked around and fragmented would change the surface composition, and then you would see a different surface color for tiny TNOs compared to their larger siblings. So it's really fascinating to see that the smallest objects are somehow 'remembering' and preserving the history of how they were made,” said Northern Arizona University PhD candidate Anastasia Morgan, who led the study of color and composition.

“These dynamically ‘hot’ TNOs retain a signature of where they were born, even though they’ve been orbitally scrambled since then,” said co-author David Trilling of Northern Arizona University.

Both the “hot” and “cold” populations seem to keep the same colors as when they were formed, with little change since the birth of the solar system.

The Webb data also allowed researchers to measure the number of objects of each size. They found that the overall size distributions for both populations were surprisingly similar.

“It's very interesting that the process of planetesimal formation ends up producing the same distribution of sizes for both cold and hot populations, despite forming in different regions of the early solar system. The process seems to be insensitive to disk conditions, producing similar planetesimal sizes whether the disk is hot or cold, and dense or fluffy,” said University of Victoria PhD candidate Marielle Eduardo, who led the study on size distribution.

Researchers also found fewer of these very small bodies than they expected based on some planet formation models. Webb discovered 27 new, remarkably dim TNOs, one so faint it is equivalent to standing on Earth and seeing a small swarm of fireflies on the Moon. The smallest one they observed has a diameter of about 3 miles (5 kilometers), which is about five times smaller than what is possible to detect with the most sensitive ground-based telescopes.

This project would not have been possible without Hubble and Webb working together to detect and characterize these TNOs. With Hubble’s sensitivity in visible light and Webb’s in infrared, the space telescopes provide more insights than either can on its own.

The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

Source: NASA's Hubble Space Telescope/News

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A superbubble scene

LHA 120-N44

TA dense field of stars fills the image, surrounded by wispy clouds of gas and dust. Pale blue and grey nebulosity forms an intricate web across the scene, with darker clouds of dust concentrated towards the lower right. Numerous bright stars appear in shades of blue, white and orange. Credit: ESA/Hubble & NASA, D. Gouliermis.

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This sprawling cosmic vista and subject of today’s ESA/Hubble Picture of the Month comes from the Large Magellanic Cloud, or LMC. The LMC is the largest of the small galaxies that orbit our Milky Way galaxy. At just 160 000 light-years away, the LMC offers a close look at highly active stellar birthsites like the nebula shown here. This nebula is named LHA 120-N44, or N44 for short, and it’s located in the constellation Dorado.

The appearance of this photogenic nebula is dominated by two features: a vast central void and a shell of dense, dusty gas. The central void is a ‘superbubble’ spanning roughly 210 by 140 light-years. The glittering stars at the centre of the void are responsible for its creation; through their powerful stellar winds and explosive supernovae, these stars have expelled much of the gas from which they were born.

When the stars of N44’s central star cluster swept away this gas, the expelled gas formed a shell around the superbubble. New stars are forming in this compressed gas shell, making N44 an interesting target for researchers studying the process of star formation. In particular, astronomers have turned to this nebula as an ideal place to time this process from start to finish. Their goal is to understand how long it takes from the collapse of cold gas clouds into dense knots to the moment nuclear fusion ignites in the heart of a newborn star.

Researchers used Hubble to survey N44 and take a census of its stars, cataloguing nearly half a million stars within the cluster as well as interlopers drifting in front of it. Of the stars surveyed, nearly 30 000 are what astronomers call pre-main-sequence stars, which have yet to begin fusing hydrogen into helium in their cores. This treasure trove of baby stars was discoverable thanks to the high sensitivity and fine spatial resolution of Hubble’s instruments that can pick out faint objects in crowded clusters.

The gas shell surrounding the superbubble is energised by ultraviolet radiation from massive stars, causing it to glow and highlighting several distinct features. Each feature within the broader N44 star-forming complex was catalogued by astronomer Karl Henize in the 1950s. One feature is a smaller bubble, catalogued as N44F, that is located near the upper-right corner of this image. N44F is an interstellar bubble blown by the intense stellar winds of a single hot and massive star. As this previously released Hubble closeup shows, the star’s furious winds and radiation have sculpted the surrounding bubble and created pillars of dusty gas.

The data used to create this image come from an observing programme (#14689; PI: Gouliermis) that aimed to probe stars in the N44 complex that have not yet begun fusing hydrogen into heavier elements in their cores. These data help to determine how long the process of star formation takes, as well as what masses newborn stars typically have. Hubble's sensitive observations of the lowest-mass stars in this region open a new window onto star formation in regions that, like the LMC or the galaxies of the early Universe, are poor in elements heavier than helium.

Source: ESA/Hubble/potm

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Links

• Image on ESA website
• Video: Space Sparks episode 28
• Video: Pan of LHA 120-N44
• Video: Zoom into LHA 120-N44

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