'Born-again' star offers rare chance to watch stellar evolution in real time

This image captures the ancient planetary nebula ejected by Sakurai's Object when the star died for the first time. The star itself is not visible, as it was captured before it began brightening again. Credit :ESO, 2004

Licence type: Attribution (CC BY 4.0)

Astronomers have confirmed that one of the fastest-changing stars ever observed has entered a new stage of its evolution, offering a rare opportunity to watch a star's life unfold on human timescales.

Using the European Southern Observatory's Very Large Telescope (VLT) in Chile, researchers, involving scientists from The University of Manchester and The Valongo Observatory, studied Sakurai's Object, a rare 'born-again' star that unexpectedly burst back to life in 1996 after reaching the final stages of its evolution.

Their findings, published today in Monthly Notices of the Royal Astronomical Society, show that the star has entered a new phase of its evolution, developing the powerful stellar wind characteristic of Wolf-Rayet stars.

The research provides new insight into the final stages of stellar evolution and helps astronomers test theories that would otherwise take thousands or millions of years to verify.

Professor Albert Zijlstra, from Jodrell Bank Centre for Astrophysics at The University of Manchester, said: "Most stars evolve so slowly that major changes take place over timescales far longer than a human lifetime. As a result, we usually have to piece together snapshots of stellar evolution by comparing different stars at different stages of their lives.

"Sakurai's Object offers something far rarer. It is one of the very few stars known to have changed dramatically within just a few decades, giving us the opportunity to watch stellar evolution unfold in real time. Thirty years ago, the star had a temperature similar to our Sun. Now, it is five times as hot, the fastest rate of increase ever seen.

'Born-again' star animation

"With our observations, we can test theories of how stars evolve and gain new insights into one of the shortest and least understood phases in the life of a dying star."

The scientists believe the star was similar to our Sun, but had already ended nuclear burning and begun its journey towards becoming a white dwarf - the hot, dense core left behind after an ordinary star dies. It underwent a rare event known as a "very late thermal pulse", when a layer of helium deep inside the dead star suddenly reignites. The event caused the star to rapidly expand, cool and eject large amounts of material into space, temporarily returning to an earlier stage of its life, leading astronomers to describe it as a "born-again" star.

Only two stars have ever been directly observed undergoing this type of dramatic rebirth: Sakurai's Object and V605 Aquilae. Following its outburst, Sakurai's Object became hidden behind thick clouds of gas and dust released during the eruption, making it difficult to study directly.

To investigate its current state, the team analysed light collected by the VLT and compared it with sophisticated computer models that simulate the atmospheres and powerful winds of Wolf-Rayet stars.

The observations revealed distinctive signatures of carbon and helium, allowing the researchers to find its temperature, chemical composition and the characteristics of its stellar wind.

Their analysis suggests the star's surface temperature is currently between around 27,000 and 36,000 degrees Kelvin, showing that it is reheating following its dramatic eruption nearly three decades ago.

Professor Zijlstra added: "One of the key questions is how quickly Sakurai's Object should recover after its dramatic eruption.

"Our measurements show that the star is reheating more gradually than some earlier models predicted. That gives us an important way of testing which theories best describe what happens when a dying star briefly springs back to life.

"As we continue to monitor the star over the coming years, we expect to learn much more about this remarkable phase of stellar evolution."

The findings also suggest that Sakurai's Object is at an earlier stage of its evolution than V605 Aquilae, which experienced a similar event around 80 years ago.

The team will continue observing Sakurai's Object as it continues reheating and resumes its journey towards becoming a white dwarf, learning more about one of the most rapid and unusual phases of stellar evolution ever observed.

Source: Royal Astronomical Society (RAS)/Research Highlights

---

Media contacts:

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

Jessica Marsh
The University of Manchester
Mob: +44 (0)7780 281312
jessica.marsh@manchester.ac.uk

---

Science contacts:

Professor Albert Zijlstra
The University of Manchester
albert.zijlstra@manchester.ac.uk

---

Images & captions

Sakurai's Object

Caption: This image captures the ancient planetary nebula ejected by Sakurai's Object when the star died for the first time. The star itself is not visible, as it was captured before it began brightening again.

Credit: ESO, 2004

‘Born-again’ star still

Caption: A still image of the animation showing Sakurai's Object as it was captured three years ago.

Credit: Peter van Hoof

---

Further information

The paper 'The emergence of a [WC] star in Sakurai's object' by Marcolini et al. has been published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/stag1533.

---

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 internationally. Its more than 4,000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

The RAS accepts papers for its journals based on the principle of successful peer review, following 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.

Download the RAS Supermassive podcast

Submitted by Sam Tonkin on Wed, 16/09/2026 - 10:00

---

Japanese Supercomputer Explains Webb's Little Red Dots

Visualization of the simulation by ATERUI III showing a rapidly growing black hole surrounded by gas. Red indicates areas of higher temperature. (Credit: Sunmyon Chon, Takaaki Takeda, 4D2U Project, NAOJ) - Image (485KB)

---

Of all the discoveries from the James Webb Space Telescope, the multitude of Little Red Dots it has observed is one of the most enigmatic. Now, simulations using the Japanese Supercomputer ATERUI III have explained the nature of the Little Red Dots without requiring any exotic assumptions. The simulations show that the Little Red Dots are black holes growing at a rate that would be impossible today thanks to the conditions in the early Universe.

In this study, a research team led by Sunmyon Chon at the Max Planck Institute for Astrophysics used the ATERUI III supercomputer at the National Astronomical Observatory of Japan to conduct the most detailed cosmological simulations to date of conditions in the early Universe. The team's simulation started with the conditions surrounding a galaxy in the early Universe, then zoomed-in to individual gas clouds. These computationally intense simulations were made possible by ATERUI III's high-resolution computing power.

The simulations show that in the early Universe, intense far-ultraviolet (FUV) radiation from nearby galaxies suppresses star formation in gas clouds, so that rather than forming many little stars the gas can form a single, supermassive star, which then collapses into a black hole seed. The simulations show that, once formed, these black hole seeds are surrounded by dense gas disks. This environment traps radiation, enabling the black holes to grow at rates dozens of times faster than would be possible in the modern Universe. The simulated properties of these rapidly growing black holes provide a good match to the Little Red Dots (LRDs) observed by the James Webb Space Telescope (JWST).

A long-standing mystery in Astronomy has been how the super-massive black holes, with masses millions or even billions of times that of the Sun, observed in the early Universe appeared so quickly, in less than 600 million years after the Big Bang. JWST was expected to answer this question by allowing us to see fainter, more distant galaxies. Because light travels at a finite speed, looking at more distant objects is like looking back in time. When we observe a galaxy 11 billion light-years away, that light has had to travel 11 billion years to reach us. That light shows us what the galaxy looked like when the light left 11 billion years ago. Likewise, the light from a galaxy 12 billion light-years away is 12 billion years old.

JWST allows us to look back farther in time than ever before, but instead of finding the answer to the rapid growth of black holes, it revealed a population of small enigmatic extremely red objects which were dubbed Little Red Dots (LRDs). These new simulations show that the LRDs are the answer to the black hole growth mystery, and a deceptively simple answer at that. In the simulation, these results happened as a natural consequence of the conditions in the early Universe, without requiring any exotic assumptions or chance accidents. This is important for explaining the ubiquity of LRDs. As JWST continues to reveal more LRDs and future telescopes probe deeper into the early Universe, this new model provides a powerful roadmap for understanding how the cosmos evolved.

Visualization video of the simulation by ATERUI III showing the evolution of the Universe up to the appearance of supermassive black holes. (Credit: Sunmyon Chon, Takaaki Takeda, 4D2U Project, NAOJ) - The video and more details are available at: YouTube

Source: National Astronomical Observatory of Japan (NAOJ)/News

---

Detailed Article(s)

Japanese Supercomputer Explains Webb's Little Red Dots
Center for Computational Astrophysics

Release Information

Researcher(s) Involved in this Release

Sunmyon Chon (Max Planck Institute for Astrophysics)
Shingo Hirano (Kanagawa University)
Tomoaki Ishiyama (Chiba University)
Seok-Jun Chang (Max Planck Institute for Astrophysics)
Volker Springel (Max Planck Institute for Astrophysics)
Coordinated Release Organization(s)
Max Planck Institute for Astrophysics
National Astronomical Observatory of Japan, NINS
Kanagawa University
Chiba University

---

Paper(s)

Sunmyon Chon et al. “Overmassive black holes and little red dots naturally form in simulations” in Nature, DOI: 10.1038/s41586-026-10985-8

---

Related Link(s)

• Japanese Supercomputer Explains Webb's Little Red Dots (Chiba University)


• How the Universe’s First Supermassive Black Holes Were Born (Max Planck Institute for Astrophysics)


• Radiative Transfer Shapes Hydrogen Lines in Little Red Dots (Max Planck Institute for Astrophysics)
  (May 1, 2026)

---

STScI Scientists Part of Collaboration Receiving 2027 Berkeley Prize

Pandora's Cluster

Astronomers estimate 50,000 sources of near-infrared light are represented in this image from NASA’s James Webb Space Telescope. Their light has travelled through varying distances to reach the telescope’s detectors, representing the vastness of space in a single image. A foreground star in our own galaxy, to the right of the image center, displays Webb’s distinctive diffraction spikes. Bright white sources surrounded by a hazy glow are the galaxies of Pandora’s Cluster, a conglomeration of already-massive clusters of galaxies coming together to form a megacluster. The concentration of mass is so great that the fabric of spacetime is warped by gravity, creating an effect that makes the region of special interest to astronomers: a natural, super-magnifying glass called a “gravitational lens” that they can use to see very distant sources of light beyond the cluster that would otherwise be undetectable, even to Webb.

These lensed sources appear red in the image, and often as elongated arcs distorted by the gravitational lens. Many of these are galaxies from the early universe, with their contents magnified and stretched out for astronomers to study. Other red sources in the image have yet to be confirmed by follow-up observations with Webb’s Near-Infrared Spectrograph (NIRSpec) instrument to determine their true nature. One intriguing example is an extremely compact source that appears as a tiny red dot, despite the magnifying effect of the gravitational lens. One possibility is that the dot is a supermassive black hole in the early universe. NIRSpec data will provide both distance measurements and compositional details of selected sources, providing a wealth of previously-inaccessible information about the universe and how it has evolved over time. This image was taken as part of the UNCOVER Cycle 1 Treasury program. Image Processing: Alyssa Pagan (STScI)

---

Scientists from the Space Telescope Science Institute (STScI) are members of the collaboration that has been awarded the 2027 Lancelot M. Berkeley–New York Community Trust Prize for Meritorious Work in Astronomy as part of their work with the UNCOVER project. The Berkeley prize is awarded annually for highly meritorious work in advancing the science of astronomy during the previous year.

According to the prize citation, the UNCOVER collaboration is being honored with the 2027 Berkeley prize for “combining the power of telescopes and gravitational lenses to reveal the contents of the distant universe. Through spectroscopic studies, the team has discovered galaxies at cosmic dawn, including large populations of luminous galaxies and supermassive black holes in the early universe.”

UNCOVER is a Cycle 1 Treasury program on NASA’s James Webb Space Telescope. UNCOVER — which stands for Ultradeep NIRSpec and NIRCam Observations before the Epoch of Reionization — conducted ultradeep imaging and spectroscopy of and around Abell 2744, a massive group of galaxies also known as “Pandora's Cluster.” The large mass of this cluster causes it to act as a powerful magnifying glass, bending the light from faraway background galaxies in a phenomenon known as gravitational lensing.

The primary science goals of the UNCOVER program are to constrain the physical properties of the first galaxies that formed in the universe; to explore how and when galaxies irradiated their environment and reionized the surrounding neutral gas; to discover dust-obscured galaxies out to a high redshift to probe star formation early in the universe; and to build a fuller picture of star formation quenching in galaxies over cosmic time.

Awarded annually since 2011 by the American Astronomical Society (AAS) and supported by a grant from The New York Community Trust, the Berkeley prize includes a monetary award and an invitation to give the closing plenary lecture at the AAS winter meeting. The 249th AAS meeting will be held in Salt Lake City, Utah, from 10 to 14 January 2027.

Each year the three AAS Vice Presidents, in consultation with the Editor in Chief of the AAS journals, select the Berkeley prize winner for meritorious research published within the preceding 12 months. This year’s prize recognizes the UNCOVER team for three recent articles published in The Astrophysical Journal. The first and the second present an overview of the UNCOVER project, summarize its science goals, and characterize the initial imaging and final spectroscopy from the project. The third introduces a key result from the project: evidence that the population of faint, compact “little red dots” seen by JWST in the early universe is dominated by reddened, actively accreting black holes rather than simply dusty star-forming galaxies. The team showed that these reddened active galactic nuclei are far more numerous at high redshifts than previously recognized.

The UNCOVER team consists of more than 50 people located across the globe co-led by Sedona Price at STScI, and including STScI astronomers Dan Coe and Susan Kassin, along with Camilla Pacifici, formerly at STScI. The Berkeley prize will be accepted on behalf of the collaboration by Ivo Labbé (Swinburne University of Technology) who, along with Rachel Bezanson, is the co-principal investigator of UNCOVER.

The Space Telescope Science Institute is expanding the frontiers of space astronomy by hosting the science operations center of the Hubble Space Telescope, the science and mission operations centers for the James Webb Space Telescope, and the science operations center for the Nancy Grace Roman Space Telescope. STScI also houses the Barbara A. Mikulski Archive for Space Telescopes (MAST) which is a NASA-funded project to support and provide to the astronomical community a variety of astronomical data archives, and is the data repository for the Hubble, Webb, Roman, Kepler, K2, TESS missions and more. STScI is operated by the Association of Universities for Research in Astronomy in Washington, D.C.

Source: Space Telescope Science Institute (STScI)/Press Releases

---

About This Release

Credits:

Media Contact

Christine Pulliam
Space Telescope Science Institute, Baltimore

Susanna Kohler
American Astronomical Society, Washington

Permissions: Content Use Policy

Contact Us: Direct inquiries to the News Team.

Related Links and Documents

American Astronomical Society Press Release

---

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

---

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!

---

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)

---

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

---

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

---

'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)

---

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

---

Media contacts:

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

---

Science contacts:

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

---

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)

---

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.

---

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.

Download the RAS Supermassive podcast

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

---

Smithsonian Astrophysical Observatory Receives $3.6M from Gordon and Betty Moore Foundation to Advance Next-Generation Event Horizon Telescop

A still image simulation of the kinds of imagery and video that the ngEHT will make possible.
Credit: Smithsonian Astrophysical Observatory/S. Doeleman & N. Conroy

---

The funding will support expansions to the telescope collaboration that will enable the first full-color, high-definition movies of black holes

Cambridge, MA (September 17, 2026) — The Smithsonian Astrophysical Observatory (SAO), part of the Center for Astrophysics, has been awarded $3,597,771 from the Gordon and Betty Moore Foundation (GBMF) to enable the first full-color, high-definition movies of black holes.

The three-year award will advance the next-generation Event Horizon Telescope (ngEHT) by supporting construction of the new Tenerife Event-horizon Antenna, site preparation at three additional locations, and the design of a pathfinder telescope for Mount Kilimanjaro.

“This award marks an exciting turning point for the ngEHT,” said Sheperd Doeleman, astrophysicist at SAO and the project’s principal investigator. “We’re moving from successful prototypes and designs to building the instruments and sites that will make high-definition, full-color movies of black holes possible.”

By tracking the motion of matter and light near the edge of the black hole in our neighboring M87 galaxy , the project will help scientists investigate some of the most fundamental questions in physics, including: Does Einstein’s theory of gravity hold under the black hole’s extreme conditions? How do they accrete matter and grow over cosmic time? How do spinning black holes power jets that can pierce entire galaxies?

<

Diagram of the dish structure for construction of new radio dishes for the Next Generation Event Horizon Telescope.
Credit: ngEHT

“This Gordon and Betty Moore Foundation funding continues their generous commitment to the cutting edge of astronomy,” said Lisa Kewley, director of the Center for Astrophysics | Harvard & Smithsonian and the Smithsonian Astrophysical Observatory. “We are proud to receive their support, which will help advance the ngEHT and bring its quest to understand black holes closer to reality.”

Completing the Tenerife Event-horizon Antenna: A major focus of the award is the completion of the Tenerife Event-horizon Antenna, or TEA, in the Canary Islands. The project team will develop and engineer a new digital system at the TEA capable of processing the unprecedented data output of the ngEHT. The upgrade will increase the antenna’s bandwidth and frequency coverage, as well as improving its ability to compensate for atmospheric turbulence. It will also establish a model for future ngEHT telescope sites.

Preparing the Global Array for Expansion: The grant will also fund the development of three future ngEHT telescope sites. It will support assessments to evaluate both engineering design plans and environmental and cultural impact of telescope sites in San Pedro Mártir, Mexico; Las Campanas, Chile; and Mt. Jelm, Wyoming. This work will include infrastructure planning, site assessments, architectural layouts, and environmental reviews.

Designing a Kilimanjaro Pathfinder Telescope: The award will further support a collaboration of SAO with the Open University of Tanzania to design a mobile, transportable pathfinder dish for near Mt. Kilimanjaro in Tanzania.This small, mobile radio telescope will test whether the Kilimanjaro Saddle area is suitable for a full-scale ngEHT facility. This design will contribute to a broad international feasibility study, and any future development would proceed through close engagement with local communities, educational institutions, government agencies, environmental organizations, and local cultural groups.

Earlier support from the Gordon and Betty Moore Foundation helped advance the ngEHT’s key telescope systems, including its state-of-the-art digital backend, its high-frequency data receivers, and a new 13-meter antenna. The project’s international partners are working toward a distributed array capable of producing increasingly detailed and dynamic images of black holes in the early 2030s.

“This support brings us closer to seeing how black holes change in real time and to answering some of the biggest questions in modern physics,” said Doeleman.

The award, titled “The Next-Generation Event Horizon Telescope: Site Development Phase II,” supports work from July 1, 2026, through June 30, 2029.

This project is funded by the Gordon and Betty Moore Foundation, Grant GBMF14361.

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

---

About the Gordon and Betty Moore Foundation:

Gordon and Betty Moore established the foundation to create positive outcomes for future generations. In pursuit of that vision, we advance scientific discovery, environmental conservation, and the special character of the San Francisco Bay Area. Visit Moore.org and follow @MooreFound.

About the Next Generation Event Horizon Telescope:

The next generation Event Horizon Telescope (ngEHT) will capture the sharpest images and videos of black holes. Building on the success of the original Event Horizon Telescope (EHT) and its release in 2019 of the first black hole picture, the ngEHT develops state-of-the-art technology to modernize existing instrumentation and realize new capabilities while expanding the geographical footprint of the array with new dishes at optimized locations around the world. By achieving the highest angular resolution possible from the surface of the Earth, the ngEHT will produce full-color, high-definition black hole “cinema” to test Einstein’s theory of gravity, and the fundamental nature of supermassive black holes.

About the Smithsonian Astrophysical Observatory:

The Smithsonian Astrophysical Observatory is a research center of the Smithsonian Institution and part of the Center for Astrophysics, the largest astrophysics research center in the world. The Observatory has been a pioneer in space exploration and discovery since its founding in 1890. Today, in addition to performing groundbreaking astronomical research, SAO operates multiple satellites, including NASA's Chandra X-ray Observatory, and runs the Minor Planet Center that tracks all known asteroids in the solar system.

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.

---

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

Image of galaxy NGC 1386, taken with Legacy Surveys
DR10

---

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

---

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.

---

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

---

• 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.

---

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

---

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

---

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

---

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)

---

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

---

Contact:

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

---

Authors:

Kritti Sharma (Lead author and a graduate student)

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

---

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)

---

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.

---

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

---

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

---

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

---

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.

---