JWST Spies a Potential Microlensed Massive Binary Star System

The galaxy cluster MACS J0416.1-2403, as seen by the Hubble Space Telescope and JWST

Credit: Image: NASA, ESA, CSA, STScI, Jose Diego (IFCA), Jordan D'Silva (UWA), Anton Koekemoer (STScI), Jake Summers (ASU), Rogier Windhorst (ASU), Haojing Yan (University of Missouri); Image Processing: Joseph DePasquale (STScI)

JWST image of the gravitationally lensed Cosmic Gems arc, in which multiple individual star clusters are visible. Credit: ESA/Webb, NASA & CSA, L. Bradley (STScI), A. Adamo (Stockholm University) and the Cosmic Spring collaboration; CC BY 4.0

Glimpses of Single Stars

Galaxy clusters, the largest gravitationally bound structures in the universe, create the conditions necessary for astronomers to perform an extraordinary feat: examine individual massive stars and star clusters at far greater distances than our telescopes can typically achieve. This is possible thanks to gravitational lensing, the bending of spacetime by an immense mass, which warps and magnifies the light from more distant objects.

These glimpses of single stars and star clusters offer a rare chance to study massive stars in our universe’s distant past directly. In particular, these observations allow us to probe whether factors like the multiplicity fraction — how many massive stars are in binary or multiple systems — have changed over cosmic time.

The Warhol arc is the pinkish galaxy at the center of this image. Adapted from NASA, ESA, CSA, STScI, Jose Diego (IFCA), Jordan D’Silva (UWA), Anton Koekemoer (STScI), Jake Summers (ASU), Rogier Windhorst (ASU), Haojing Yan (University of Missouri); Image Processing: Joseph DePasquale (STScI)

Peering Through a Gravitational Lens

In a recent research article, a team led by Hayley Williams (University of Minnesota) reported on their examination of an intriguing source in a gravitationally lensed galaxy called the “Warhol arc.” This galaxy, located at a redshift of z = 0.94 (when the universe was roughly 6 billion years old), is gravitationally lensed by the massive galaxy cluster MACS J0416.1−2403. The cluster is located at a redshift of z = 0.396, corresponding to when the universe was about 9.4 billion years old.

Using data from the JWST Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) program and the Canadian NIRISS Unbiased Cluster Survey (CANUCS), Williams’s team analyzed a source in the Warhol arc called W2, which previous work suggests is either a binary star system or a small star cluster.

Top row: The Warhol arc during four epochs of JWST observations. Bottom row: On the left, a magnified image of W2 during the first epoch. The remaining images show the difference in brightness between subsequent epochs and the first epoch. Click to enlarge. Credit: Williams et al. 2026

Multiplicity and Microlensing

Across four epochs spanning 126 days, the JWST observations show the source W2 within the Warhol arc. Williams and collaborators performed spectral fitting of the JWST light curves to investigate the multiplicity of the source. They found that the data are best matched by a binary system containing stars with temperatures of 3500K and 12600K.

W2 varies between observations in both brightness and color, a fact that the authors suggested is due to microlensing by a star within the lensing galaxy cluster, rather than variability within the binary system itself. Under this hypothesis, the orbital motions of the binary bring the stars across the microlensing caustic — a region in which the magnification is exceptionally high — and the brightness and color of W2 vary as the components of the binary approach and recede from the caustic.

Williams and collaborators also performed stellar population modeling to explore the binary configurations that could match the observations. They found that the stars likely have masses of 21–24 solar masses, with one being a cool red supergiant and the other a hot, main-sequence companion. Depending on the precise evolutionary stage of the binary, it’s possible that one of the stars is nearing a supernova explosion. Lending more support to the binary system hypothesis, the microlensing measurements constrain W2 to be no larger than 90 au — too small for even a compact star cluster.

The team closed by proposing further observations of W2’s position to rule out the possibility that the microlensing rate there is unusually high, an outcome that may suggest that microlensing of two unrelated stars, rather than a binary system, is responsible for these observations.

By Kerry Hensley

Citation

“JWST’s PEARLS: A Candidate Massive Binary Star System in a Lensed Galaxy at Redshift 0.94,” Hayley Williams et al 2026 ApJ 997 292. doi:10.3847/1538-4357/ae2003

Source: American Astronomical Society/AAS/Nova

---

VLITE Marks 11 Years of Capturing the Dynamic Radio Sky

VLITE 11 year sky coverage map
Credit: NRL. Hi-Res File

---

A collaboration between the U.S. Naval Research Laborato,hrry and the National Radio Astronomy Observatory celebrates over a decade of commensal observing with the VLA

The U.S. National Science Foundation National Radio Astronomy Observatory (NSF NRAO) and the U.S. Naval Research Laboratory (NRL) are celebrating the 11th anniversary of the VLA Low-band Ionosphere and Transient Experiment (VLITE), a pioneering program that has opened new windows into the low-frequency radio universe.

Launched in late 2014, VLITE operates commensally with the U.S. National Science Foundation Very Large Array (NSF VLA), continuously recording low-frequency data while the NSF VLA conducts its regular science observations. This innovative model has enabled VLITE to build an unprecedented dataset of the dynamic radio sky, without interrupting or altering the array’s primary research projects.

“VLITE was envisioned as an opportunistic experiment, but it has evolved into a powerhouse dataset for studying the ionosphere, transients, and cosmic radio emission,” said NSF VLA Director Dr. Trish Henning. “Its success demonstrates how strategic collaborations can multiply the scientific return of existing infrastructure.”

As of its 11th anniversary, VLITE has amassed a remarkable record of continuous operation and scientific impact:

Sky coverage:

98% of the sky north of –40° declination observed to 49 minutes

50% of the sky north of –40° declination observed to 190 minutes

1% of that same sky observed to 132 hours


Data production:

More than 3.8 million META files processed

66,846 hours of data collected (representing 69% of wall-clock time)

759,760 archived images


Scientific impact:

93 peer-reviewed papers using or referencing VLITE data

6,256 total citations

75,429 combined reads across those publications


Additionally, seven high-impact papers have been published in Nature, Nature Astronomy, and Science.

“The sustained productivity and science reach of VLITE highlight the value of commensal observing,” said a scientist from NRL’s Remote Sensing Division. “By listening to the low-band universe alongside the VLA, we’ve captured both expected and surprising phenomena—from ionospheric structure to astrophysical transients.”

VLITE’s success provides a crucial foundation for future low-frequency efforts at the VLA, including technology pathfinding for the next-generation VLA (ngVLA) and potential extensions of the VLITE model to expanded frequency coverage or continuous transient monitoring.

“The collaboration between NRL and NSF NRAO continues to showcase what’s possible when innovative engineering, operations, and science intersect,” said Director Trish Henning. “As we look ahead, VLITE remains a testament to what long-term vision and cooperation can achieve.”

Source: National Radio Astronomy Observatory (NRAO)/News

---

Press Contacts:

Corrina Jaramillo Feldman
Sr. Public Information Officer
cfeldman@nrao.edu | Tel: +15056408189

---

About VLITE

The VLA Low-band Ionosphere and Transient Experiment (VLITE) is a collaborative program between the U.S. Naval Research Laboratory and the U.S. National Science Foundation National Radio Astronomy Observatory. VLITE operates commensally with the NSF VLA, recording data in the 320–384 MHz frequency range during regular NSF VLA observations to study astrophysical and geophysical phenomena.

About NRAO

The National Radio Astronomy Observatory is a facility of the U.S. National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

About the U.S. Naval Research Laboratory

NRL is a scientific and engineering command dedicated to research that drives innovative advances for the U.S. Navy and Marine Corps from the seafloor to space and in the information domain. NRL, located in Washington, D.C. with major field sites in Stennis Space Center, Mississippi; Key West, Florida; Monterey, California, and employs approximately 3,000 civilian scientists, engineers and support personnel.

NRL offers several mechanisms for collaborating with the broader scientific community, within and outside of the Federal government. These include Cooperative Research and Development Agreements (CRADAs), LP-CRADAs, Educational Partnership Agreements, agreements under the authority of 10 USC 4892, licensing agreements, FAR contracts, and other applicable agreements.

---

Keck Observatory observations help constrain a long-predicted pathway for black hole formation

Birth of a black hole: These images and animation shows a shell of thick gas and dust (red) expelled from the outer layers of a star as its core collapsed into a black hole. The inner regions show a heated sphere of gas continuing to fall into the black hole that is hidden inside the hot gas. Credit: Keith Miller, Caltech/IPAC – SELab. Video

---

Maunakea, Hawaiʻi – Astronomers using W. M. Keck Observatory on Maunakea, Hawaiʻi Island contributed key observations to the identification of a rare stellar death in which a massive star appears to have collapsed directly into a black hole without first exploding as a supernova. The event occurred in the Andromeda galaxy and provides strong observational support for a long-theorized but rarely confirmed route to black hole formation.

The study, led by researchers at Columbia University, is published in today’s issue of the journal Science and combines archival space-based data with targeted ground-based follow-up observations from multiple observatories.

“This has probably been the most surprising discovery of my life,” said Kishalay De, professor of astronomy at Columbia University and lead author of the study. “The evidence of the disappearance of the star was lying in public archival data, and nobody noticed it for years until we picked it out.”

A quiet stellar death in Andromeda

The object, designated M31-2014-DS1, was a supergiant star located about 2.5 million light-years from Earth in the Andromeda galaxy. When it formed, the star was roughly 13 times the mass of the Sun. Over its lifetime, powerful stellar winds stripped away much of that mass, leaving it with about five times the mass of the Sun at the end of its life.

Archival observations from NASA’s NEOWISE mission revealed that the star gradually brightened in infrared light over several years before fading dramatically and disappearing from view. Unlike a typical supernova, the event showed no evidence of a powerful outward explosion. Instead, it left behind a shell of dust and a faint infrared glow.

“The dramatic and sustained fadig of this star is very unusual, and suggests a supernova failed to occur, leading to the collapse of the star’s core directly into a black hole,” De said.

Critical follow up from the ground

To better constrain the nature of the event, the team conducted follow-up observations using the Near-Infrared Echellette Spectrograph (NIRES) on the Keck II Telescope, with observing time awarded via the NASA-Keck partnership.

Prior to the Keck observations, there were no ground-based infrared spectra of the source at sufficient sensitivity to test whether the star had truly faded at infrared wavelengths.

NIRES is optimized for studying extremely faint infrared sources and isparticularly well suited to probing dusty stellar remnants. The data placed important limits on the temperature, composition, and evolution of the material left behind after the star disappeared, including faint emissio from material expelled by the star, helping rule out alternative explanations such as an unusual supernova or intrinsic stellar variability.

“It was only with Keck’s sensitivity in the near infrared that we could confirm the star had truly faded at all wavelengths,” De said. “Even with NIRES, the source was barely detected, which allowed us to rule out normal hints of stellar variability or dust obscuration and strengthened the case that the star had genuinely disappeared.”

The Keck observations were analyzed alongside data from space-based telescopes and other ground-based facilities as part of a coordinated, multi-wavelength campaign.

A Rare View into Direct Collapse

Astronomers have long known that black holes originate from massive stars, but direct observational evidence of that transformation has been scarce. While gravitational-wave detections have revealed black hole mergers across the universe, they do not show how those black holes initially formed.

Only one other candidate direct-collapse event has been reported previously, but it was significantly more distant and fainter, leaving its interpretation uncertain. The relative proximity of Andromeda and the quality of the available data make M31-2014-DS1 a particularly compelling case.

“We’ve known that black holes must come from stars,” said Morgan MacLeod, lecturer in astronomy at Harvard University and co-author of the study. “With events like this, we’re getting to watch it happen, and are learning a huge amount about how that process works along the way.”

Looking ahead

The findings suggest that direct collapse may be a more common outcome for massive stars than previously assumed. Future infrared surveys, combined with sensitive ground-based facilities like Keck Observatory, are expected to uncover additional examples and further clarify the physical conditions that determine how massive stars end their lives.

Source: W.M. Keck Observatory/Science News

---

Related Links:

• Columbia Press Release


• Flatiron Institute Press Release


• Science Paper

---

About NIRES

The Near-Infrared Echellette Spectrograph (NIRES) is a prism cross-dispersed near-infrared spectrograph built at the California Institute of Technology by a team led by Chief Instrument Scientist Keith Matthews and Prof. Tom Soifer. Commissioned in 2018, NIRES covers a large wavelength range at moderate spectral resolution for use on the Keck II telescope and observes extremely faint red objects found with the Spitzer and WISE infrared space telescopes, as well as brown dwarfs, high-redshift galaxies, and quasars. Support for this technology was generously provided by the Mt. Cuba Astronomical Foundation.

About W.M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaiʻi feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. For more information, visit: www.keckobservatory.org

NASA’s Hubble Captures Light Show Around Rapidly Dying Sta

Egg Nebula

NASA’s Hubble Space Telescope reveals the clearest view yet of the Egg Nebula. This structure of gas and dust was created by a dying, Sun-like star. These newest observations were taken with Hubble’s Wide Field Camera 3. Credit Image: NASA, ESA, Bruce Balick (UWashington)

Egg Nebula Compass

This image of the Egg Nebula was captured by the Hubble Space Telescope’s WFC3 (Wide Field Camera 3). The image shows a scale bar, compass arrows, and color key for reference.Credit Image: NASA, ESA, Bruce Balick (UWashington)

Exploring the Structure of the Egg Nebula

This visualization examines the Hubble Space Telescope image of the Egg Nebula and showcases the shape and development of its three-dimensional components. The dying star has repeatedly ejected thin shells of gas and dust over the last 5,000 years. During the last 400 years, bipolar lobes have burst forth. This central activity is hidden behind a dense dusty disk. The light from the star, blocked by the disk and lobes, escapes toward the poles and creates a twin searchlight appearance. Credit Visualization: NASA, ESA, STScI, Christian Nieves (STScI), Frank Summers (STScI); Narration: Frank Summers (STScI); Script Writer: Frank Summers (STScI); Audio: Danielle Kirshenblat (STScI); Music: Christian Nieves (STScI)

---

This stunning image from NASA’s Hubble Space Telescope reveals a dramatic interplay of light and shadow in the Egg Nebula, sculpted by freshly ejected stardust. Located approximately 1,000 light-years away in the constellation Cygnus, the Egg Nebula features a central star obscured by a dense cloud of dust — like a “yolk” nestled within a dark, opaque “egg white.” Only Hubble’s sharpness can unveil the intricate details that hint at the processes shaping this enigmatic structure.

It is the first, youngest, and closest pre-planetary nebula ever discovered. (A pre-planetary nebula is a precursor stage of a planetary nebula, which is a structure of gas and dust formed from the ejected layers of a dying, Sun-like star. The term is a misnomer, as planetary nebulae are not related to planets.)

The Egg Nebula offers a rare opportunity to test theories of late-stage stellar evolution. At this early phase, the nebula shines by reflecting light from its central star, which escapes through a polar “eye” in the surrounding dust. This light emerges from a dusty disk expelled from the star’s surface just a few hundred years ago.

Twin beams from the dying star illuminate fast-moving polar lobes that pierce a slower, older series of concentric arcs. Their shapes and motions suggest gravitational interactions with one or more hidden companion stars, all buried deep within the thick disk of stardust.
Stars like our Sun shed their outer layers as they exhaust their hydrogen and helium fuel. The exposed core becomes so hot that it ionizes surrounding gas, creating the glowing shells seen in planetary nebulae such as the Helix, Stingray, and Butterfly nebulae. However, the compact Egg Nebula is still in a brief transitional phase — known as the pre-planetary stage — that lasts only a few thousand years. This makes it an ideal time to study the ejection process while the forensic evidence remains fresh.

The symmetrical patterns captured by Hubble are too orderly to result from a violent explosion like a supernova. Instead, the arcs, lobes, and central dust cloud likely stem from a coordinated series of poorly understood sputtering events in the carbon-enriched core of the dying star. Aged stars like these forged and released the dust that eventually seeded future star systems, such as our own solar system, which coalesced into Earth and other rocky planets 4.5 billion years ago.

Hubble has turned its gaze towards the Egg Nebula before. A first visible-light image from the telescope's WFPC2 (Wide Field and Planetary Camera 2) was complemented in 1997 by a near-infrared NICMOS (Near Infrared Camera and Multi-Object Spectrometer) image, giving a closer look at the light given off by the nebula. In 2003, Hubble's ACS (Advanced Camera for Surveys) yielded a new view of the Egg, showing the full extent of the ripples of dust around it. A further image from WFC3 (Wide Field Camera 3) in 2012 zoomed in on the central dust cloud and dramatic gas outflows. This new image combines the data used to create the 2012 image with additional observations from the same program to deliver the clearest look yet at this intricate cosmic egg.

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 projnewsect 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.

Source: NASA's Hubble Space Telescope/News

---

'Dark matter, not a black hole, could power Milky Way's heart'

Dark matter in the Milky Way

Artistic representation of the Milky Way, where the innermost stars move at near relativistic speeds (defined as velocities that constitute a significant fraction of the speed of light, typically considered to be 10% or more) around a dense core of dark matter, with no black hole at the centre. At greater distances, the halo part of the same invisible dark matter distribution continues to shape the motions of stars in the outskirts of our galaxy, tracing the characteristic rotation curve. Credit: Valentina Crespi et al.

Licence type: Attribution (CC BY 4.0)

Our Milky Way galaxy may not have a supermassive black hole at its centre but rather an enormous clump of mysterious dark matter exerting the same gravitational influence, astronomers say.

They believe this invisible substance – which makes up most of the universe's mass – can explain both the violent dance of stars just light-hours (often used to measure distances within our own solar system) away from the galactic centre and the gentle, large-scale rotation of the entire matter in the outskirts of the Milky Way.

The new study has been published today in Monthly Notices of the Royal Astronomical Society (MNRAS)

It challenges the leading theory that Sagittarius A* (Sgr A*), a proposed black hole at the heart of our galaxy, is responsible for the observed orbits of a group of stars, known as the S-stars, which whip around at tremendous speeds of up to a few thousand kilometres per second.

The international team of researchers have instead put forward an alternative idea – that a specific type of dark matter made up of fermions, or light subatomic particles, can create a unique cosmic structure that also fits with what we know about the Milky Way's core.

It would in theory produce a super-dense, compact core surrounded by a vast, diffuse halo, which together would act as a single, unified entity.

The inner core would be so compact and massive that it could mimic the gravitational pull of a black hole and explain the orbits of S-stars that have been observed in previous studies, as well as the orbits of the dust-shrouded objects known as G-sources which also exist nearby.

Of particular importance to the new research is the latest data from the European Space Agency's GAIA DR3 mission, which has meticulously mapped the rotation curve of the Milky Way's outer halo, showing how stars and gas orbit far from the centre.

It observed a slowdown of our galaxy's rotation curve, known as the Keplerian decline, which the researchers say can be explained by their dark matter model's outer halo when combined with the traditional disc and bulge mass components of ordinary matter.

This, they add, strengthens the 'fermionic' model by highlighting a key structural difference. While traditional Cold Dark Matter halos spread out following an extended 'power law' tail, the fermionic model predicts a tighter structure, leading to more compact halo tails.

The research has been carried out by an international collaboration involving the Institute of Astrophysics La Plata in Argentina, International Centre for Relativistic Astrophysics Network and National Institute for Astrophysics in Italy, Relativity and Gravitation Research Group in Colombia and Institute of Physics University of Cologne in Germany.

"This is the first time a dark matter model has successfully bridged these vastly different scales and various object orbits, including modern rotation curve and central stars data," said study co-author Dr Carlos Argüelles, of the Institute of Astrophysics La Plata.

"We are not just replacing the black hole with a dark object; we are proposing that the supermassive central object and the galaxy's dark matter halo are two manifestations of the same, continuous substance."

Crucially, this fermionic dark matter model had already passed a significant test. A previous study by Pelle et al. (2024), also published in MNRAS, showed that when an accretion disk illuminates these dense dark matter cores, they cast a shadow-like feature strikingly similar to the one imaged by the Event Horizon Telescope (EHT) collaboration for Sgr A*.

"This is a pivotal point," said lead author Valentina Crespi, of the Institute of Astrophysics La Plata.

"Our model not only explains the orbits of stars and the galaxy's rotation but is also consistent with the famous 'black hole shadow' image. The dense dark matter core can mimic the shadow because it bends light so strongly, creating a central darkness surrounded by a bright ring."

The researchers statistically compared their fermionic dark matter model to the traditional black hole model.

They found that while current data for the inner stars cannot yet decisively distinguish between the two scenarios, the dark matter model provides a unified framework that explains the galactic centre (central stars and shadow), and the galaxy at large.

The new study paves the way for future observations. More precise data from instruments such as the GRAVITY interferometer, on the Very Large Telescope in Chile, and thesearch for the unique signature of photon rings – a key feature of black holes and absent in the dark matter core scenario – will be crucial to test the predictions of this new model, the authors say.

The outcome of these findings could potentially reshape our understanding of the fundamental nature of the cosmic behemoth at the heart of the Milky Way.

Source: Royal Astronomical Society (RAS)/News

---

Media contacts:

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

Science contacts:

Lic Valentina Crespi
Institute of Astrophysics La Plata
valentinacrespi@fcaglp.fcaglp.unlp.edu.ar

Dr Carlos R. Argüelles
Institute of Astrophysics La Plata
valentinacrespi@fcaglp.fcaglp.unlp.edu.a

---

Further information

The paper 'The dynamics of S-stars and G-sources orbiting a supermassive compact object made of fermionic dark matter'by V. Crespi et al. has been published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/staf1854.

---

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 and review 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 peer review, in which fellow experts on the editorial boards accept the paper as worth considering. 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, 05/02/2026 - 10:53

---

NASA Telescopes Spot Surprisingly Mature Cluster in Early Universe

JADES-ID1
Credit X-ray: NASA/CXC/CfA/Á Bogdán; Infrared (JWST): NASA/ESA/CSA/STScI;
Image Processing: NASA/CXC/SAO/P. Edmonds and L. Frattare

JPEG (187.8 kb) - Large JPEG (2.8 MB) - Tiff (13.4 MB) - More Images

A Tour of JADES-ID1 - More Videos

---

A galaxy cluster pulling itself together has been spotted at a much earlier time in the universe than expected.

This “protocluster” is located about 12.7 billion light-years from Earth, or only about 1 billion years after the big bang.

Astronomers needed to combine data from NASA’s Chandra and James Webb Space telescopes to find and identify this protocluster.

Galaxy clusters are some of the largest structures in the universe and understanding how and when they form is crucial.

---

This graphic represents the discovery of what may be the most distant protocluster ever found, as described in our latest press release. By using NASA’s Chandra X-ray Observatory together with the James Webb Space Telescope (JWST), astronomers have netted an important piece in the history of the universe: when galaxy clusters, the largest structures held together by gravity, begin to form.

The main panel contains an infrared image from the JWST Advanced Deep Extragalactic Survey (JADES), a deep infrared imaging project that used more than a month of the telescope’s observing time. The white box outlines X-rays (blue) seen with Chandra.

The newly-discovered protocluster, dubbed JADES-ID1, is located about 12.7 billion light-years from Earth, or just about a billion years after the big bang. It has a mass of about 20 trillion suns and two important characteristics of a protocluster: a large number of galaxies held together by gravity (Webb sees at least 66 potential members) and a huge cloud of hot gas (detected by Chandra). So that only X-rays from the protocluster are included, only X-rays inside the white box are shown. The annotated version of the image shows circles where astronomers find some of the individual galaxies in JADES-ID1.

Most models of the universe predict that there likely would not be enough time and a large enough density of galaxies for a protocluster of this size to form at this epoch in the early universe. The previous record holder for a protocluster with X-ray emission is seen much later, about three billion years after the big bang. Therefore, the discovery of JADES-ID1 will force scientists to re-examine their ideas for how galaxy clusters — gigantic collections of galaxies, hot gas, and dark matter — first appeared in the universe.

To find JADES-ID1, astronomers combined deep observations from both Chandra and Webb. By design, the JADES field overlaps with the Chandra Deep Field South, the site of the deepest X-ray observation ever conducted. This field is thus one of the few in the entire sky where a discovery such as this could be made. The researchers found five other proto-cluster candidates in the JADES field, but only in JADES-ID1 are the galaxies seen to be embedded in hot gas. Only JADES-ID1 possesses enough mass for an X-ray signal from hot gas to be expected.

A paper describing these results appears in the latest issue of the journal Nature and is available here. The authors of the study are Akos Bogdan and Gerritt Schellenberger (Center for Astrophysics | Harvard & Smithsonian) and Qiong Li and Christopher Conselice (University of Manchester in the United Kingdom).

The earlier study led by Li was published in the Monthly Notices of the Royal Astronomical Society.

NASA's Marshall Space Flight Center in Huntsville, Alabama, 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 Telescopes Spot Surprisingly Mature Cluster in Early Universe

Source: NASA’s Chandra X-ray Observatory

---

Visual Description:

This composite image features what may be the most distant protocluster ever found; a region of space where a large number of young galaxies are being held together by gravity and hot gas. The image is presented twice, once with, and once without, annotations.

The image includes scores of glowing dots and specks of light, in white and golden hues, set against the blackness of space. This layer of the composite visual is from a deep infrared imaging project undertaken by the James Webb Space Telescope. The specks range from relatively large oval galaxies with discernible spiral arms, and glowing balls with gleaming diffraction spikes, to minuscule pinpoints of distant light. Several of those pinpoints have been circled in the annotated image, as they are part of the distant protocluster.

Layered onto the center of this image is a neon blue cloud. This cloud represents hot X-ray gas discovered by Chandra in the deepest X-ray observation ever conducted. In the annotated image, a thin white square surrounds the blue cloud. This represents Chandra’s field of observation. The X-rays from the distant protocluster located within this box are included in the composite image.

The protocluster, dubbed JADES-1, has a mass of about 20 trillionsuns. It is located some 12.7 billion light-years from Earth, or just a billion years after the big bang. The discovery of a protocluster of this size, at this epoch in the early universe, will lead scientists to re-examine their ideas for how galaxy clusters first appeared in the niverse.

---

Fast Facts for JADES-ID1:

Credit: X-ray: NASA/CXC/CfA/Á Bogdán; Infrared (JWST): NASA/ESA/CSA/STScI; Image Processing: NASA/CXC/SAO/P. Edmonds and L. Frattare
Release Date: January 28, 2026
Scale: Image is about 54 arcsec (1.1 million light-years) across.
Category: Groups & Clusters of Galaxies
Coordinates (J2000): RA 3h 32m 31.75s | Dec -27° 46´ 51.5"
Constellation: Fornax
Observation Dates: 99 observations from May 2000 to Feb 2016
Observation Time: 1743 hours 36 minutes (72 days, 15 hours, 36 minutes)

Obs. ID: 441, 582, 1672, 2239, 2312, 1213, 2405, 2406, 2409, 8591-8597, 9575, 9578, 9593, 9596, 9718, 12044-12055, 12123, 12128, 12129, 12135, 12137, 12138, 12213, 12218-12223, 12227, 12230-12234, 16175-16191, 16450-16463, 16620, 16641, 16644, 17416, 17417, 17535, 17546, 17552, 17556, 17573, 17633, 17634, 17677, 18709, 18719, 18730

Instrument: ACIS
References: Bogdán, Á; et al. 2026, Nature, in press. Available here.
Color Code: X-ray: blue; Infrared: red, green, blue
Distance Estimate: About 12.7 billion light-years from Earth (z~5.7)

---

'Red Potato' galaxy discovered by astronomers

Galaxy MQN01 J004131.9-493704 "Red Potato" at z=3.25 and its surrounding cool Lyα-emitting gas reservoir.
Credit: arXiv (2026). DOI: 10.48550/arxiv.2601.20473

---

Using the James Webb Space Telescope (JWST), an international team of astronomers has discovered a new massive and quiescent red galaxy, which they dubbed "Red Potato." The discovery was reported in a research paper published January 28 on the arXiv pre-print server.

A potato in the cosmic web

A team of astronomers led by Weichen Wang of the University of Milan, Italy, has recently observed a gas-rich cosmic web node at a redshift of approximately 3.25, designated MQN01. In general, such cosmic web nodes and protoclusters at high redshifts are known to host rich reservoirs of cool and molecular gas. Therefore, these structures are expected to be sites of exceptionally efficient formation of massive galaxies via gas accretion.

By investigating MQN01 with JWST's Near Infrared Camera (NIRCam) and Near Infrared Spectrograph (NIRSpec), Wang's team has serendipitously discovered a new massive red galaxy. Due to its morphology and color, they named it "Red Potato."

"In this work, we present the discovery of a massive quiescent galaxy in a gas-rich environment of a cosmic web node or protocluster at z ∼ 3.2, identified and spectroscopically confirmed from a JWST program," the researchers write in the paper.

Massive and quiescent

The Red Potato, or MQN01 J004131.9-493704, has a half-light radius of about 3,260 light years and stellar mass of 110 billion solar masses. The molecular gas mass of the galaxy was calculated to be less than 7 billion solar masses, which yields a molecular gas fraction smaller than 0.06.

The non-detection of carbon monoxide and sodium D-lines indicate that the Red Potato is poor in molecular and neutral gas. Moreover, no gas outflows have been detected from the galaxy. In general, the Red Potato galaxy appears to be a dispersion-dominated system according to the kinematics of ionized gas.

The study found that Red Potato has a star-formation rate (SFR) at a level of 4.0 solar masses per year, which is at least one dex below the star-forming main sequence (SFMS). This is a relatively low SFR given that the galaxy is located at the center of a large reservoir of cool circumgalactic medium (CGM).

X-ray jet causing gas turbulence

The stellar velocity dispersion of Red Potato was found to be 268 km/s, suggesting elevated levels of gas turbulence in the CGM. Furthermore, deep X-ray data point to the presence of an extended X-ray jet which most likely emanates from a neighboring luminous X-ray active galactic nucleus (AGN), indicating a certain form of jet-mode feedback acting on the Red Potato's CGM.

"We argue that the jet feedback may have led to increased CGM turbulence around the Red Potato and thus have reduced the gas accretion onto the galaxy, which is indicated by the high gas velocity dispersion measured from the Lyα and Hα line profiles," the authors of the paper conclude.

Source: Phys.org/Space News

---

Written for you by our author Tomasz Nowakowski, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive.If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

---

Publication details

Weichen Wang et al, A Quiescent Galaxy in a Gas-Rich Cosmic Web Node at z~3, arXiv (2026). DOI: 10.48550/arxiv.2601.20473

Journal information: arXiv

---

Explore further

SXDF-NB1006-2 is a young starburst galaxy experiencing ionized gas outflows, observations find

---

The Winner of the Cosmic Speed-Eating Contest

Artist's impression of a luminous quasar surrounded by a swirling accretion disk.
Credit: ESA/Hubble, NASA, M. Kornmesser; CC BY 4.0

Title: X-Ray Investigation of Possible Super-Eddington Accretion in a Radio-Loud Quasar at z = 6.13
Authors: Luca Ighina et al.
First Author’s Institution: Harvard–Smithsonian Center for Astrophysics and Italian National Institute for Astrophysics
Status: Published in ApJL

Quasars are some of the most extreme objects in the entire universe. Despite being as far as tens of billions of light-years away, they nonetheless can appear as bright as some stars in our own Milky Way. To put their brightness in perspective, one just has to consider the Sun. Compared to puny human scales, our star is a truly gargantuan object. It’s a fully functional fusion reactor, churning hydrogen into helium in its core and outputting an unfathomable amount of energy in the process. This glowing furnace is so bright that it can cook us with the heat of an oven during the day, even at a distance of more than 90 million miles (about 8 light-minutes). That distance dramatically dilutes the radiation of the Sun by the time it reaches us, as we only receive a small sliver of its total output, and yet we can still feel its heat pounding down on us when we stand beneath a clear summer sky.

However, if one were to move the Sun about 30 light-years away, it would appear completely unremarkable. You’d need to be under relatively dark skies to even spot it! The vastness of space would simply crush the output of our solar engine; however, if you place a luminous quasar at that same 30 light-year distance, its searing radiation would seem to effortlessly cross the cosmic gulf looming between the stars, scorching us relentlessly with the same heat as the Sun does today. The power of a quasar simply puts our star to shame.

Still, even quasars have limits. The source of power for these objects is a supermassive black hole. The supermassive black hole that lives at the center of our Milky Way is currently dormant. However, many supermassive black holes (especially in the early universe) actively gulp down matter, releasing tremendous energy that escapes in the form of radiation across the electromagnetic spectrum. The escaping photons bump into particles on their way out, exerting an outward pressure. If enough light is unleashed by the quasar, this pressure will actually balance against the pull of gravity, cutting off the food supply for the black hole. This negative feedback loop means that a given quasar has an upper limit to its brightness, called the Eddington luminosity, and to the speed at which it accretes matter, called the Eddington rate. The authors of today’s bite examine a particularly misbehaved quasar that seems to violate even these extreme limits.

It’s a Bird! It’s a Plane! It’s a Jet?

The authors observed the quasar RACS J032021.44−352104.1 (RACS J0320−35 for short) with several radio observatories, including the Giant Metrewave Radio Telescope, the Australia Telescope Compact Array, and the Australian Large Baseline Array. Combining this data with publicly available observations, they find that the source is “radio-loud,” or bright at very long wavelengths. Typically, this kind of emission is expected to be generated by powerful jets that are ejected from the poles of a quasar. For example, the authors compare this radio-loud quasar to similar sources, which show significant variability in the X-ray part of the spectrum. This is a tell-tale sign that the X-ray emission is also generated by these jets (which might come out in fits and spurts and thus cause fluctuations in brightness over time).

However, when the authors examine X-ray data of RACS J0320−35 taken by the Chandra X-ray Observatory, they find surprising results. The quasar is extremely luminous in X-rays, making it one of the brightest in the early universe. But despite the fact that it pumps out a huge number of these energetic photons, it seems to preferentially emit only the lower-energy band of X-rays and completely lacks the highest-energy emission that characterizes similar sources. In technical terms, the X-ray spectrum of RACS J0320−35 is incredibly “soft.” Moreover, this X-ray emission seems to be constant on the timescale of months, though further observations will be required to test if it varies on longer timescales. Still, the softness of the spectrum and weak variability of this system mean that its X-ray emission is unlikely to be produced by a jet.

The authors carefully consider a particular variety of jet — one that is sharply angled towards us. Since quasar jets often travel at incredible speeds, the special theory of relativity kicks in and causes strange behaviors. In particular, an effect called relativistic beaming can cause a source to appear much brighter if traveling towards the observer at extremely high speeds. However, they find that although relativistic beaming can explain the mysterious X-ray properties of RACS J0320−35, such a scenario is incompatible with its observed radio emission. Moreover, a lack of gamma-ray emission and weak variability are further pieces of evidence against the jet origin of the X-ray emission.

Figure 1: A plot showing the observed energy spectrum of RACS J0320−35 and the theoretical spectra predicted by several models. In particular, the green circles (visible light and ultraviolet (UV) emission), blue diamonds (X-ray emission), and red squares (radio emission) representthe real observations. The shaded pink region represents the predictions of a model that simulates a black hole spinning very slowly and accreting at super-Eddington rates. The model seems to match the observed X-ray and visible/UV emission excellently. However, explaining the observed radio emission might require conditions that violate the assumptions behind this scenario. Adapted from Ighina et al. 2025.

Limits Are Meant to Be Broken

The article presents one more fascinating possibility for the origin of the X-rays in this source. Some theoretical work and simulations show that if a black hole breaks the Eddington limit and starts accreting matter at “super-Eddington rates,” the X-ray spectrum that results can be incredibly soft. The authors find excellent agreement between the observations and the predictions from a particular model that simulates a very slowly spinning black hole (see Figure 1). This scenario seems to be a promising explanation for the X-ray emission in RACS J0320−35, which is extremely exciting for several reasons.

Many astronomers are considering super-Eddington accretion to explain the masses of early quasars and their fainter counterparts, called active galactic nuclei. Because supermassive black holes are supposed to have a cap on their accretion rate (the Eddington limit), the earliest black holes in the universe should only have been able to reach large sizes after sufficient time had passed. Astonishingly, observations from JWST are finding massive active galactic nuclei everywhere in the early universe, which seems to violate this — these black holes appear astonishingly massive despite existing for only a fraction of the universe’s current age. However, if early black holes could grow faster than expected by undergoing super-Eddington accretion, this tension might be resolved.

Despite the promising initial results of this model, there are a few caveats to the results presented in today’s article. For example, the radio jets observed from this source require a rapidly spinning black hole, which conflicts with the model assumptions. The authors note that a radio jet can be very far from a black hole, tracing its past activity. In fact, this jet may have actually spun down the central supermassive black hole by extracting energy from it, a fascinating possibility that will require both further observations and simulations to explore. Today’s bite shines a brilliant light on this possibility by analyzing RACS J0320−35, a fascinating quasar in the early universe and a stunning example that cosmic limits are meant to be broken.

Original astrobite edited by Veronika Dornan

Source: American Astronomical Society/AAS-Nova

---

About the author, Ansh Gupta:

I’m an astronomy graduate student at the University of Texas at Austin working with Steven Finkelstein. I use data from JWST to study the formation and growth of the first galaxies and black holes in the universe. In my spare time, I enjoy playing piano, reading, and making YouTube videos.

---

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

---

AES Andes announces cancellation of INNA, the industrial complex planned near Paranal

PR Image eso2602a
Cerro Paranal and the Milky Way above it

---

AES Andes announced that it will step back from the megaproject INNA, planned to be located near the European Southern Observatory’s (ESO’s) Paranal Observatory. ESO welcomes this announcement and expects that the project will be withdrawn from Chile's Environmental Assessment Service (SEA) soon, which would formally confirm INNA is not going ahead.

“When the cancellation is confirmed, we’ll be relieved that the INNA industrial complex will not be built near Paranal,” said ESO Director General Xavier Barcons. “Due to its planned location, the project would pose a major threat to the darkest and clearest skies on Earth and to the performance of the most advanced astronomical facilities anywhere in the world.”

AES Andes, a subsidiary of the US company AES Corporation, announced on Friday 23 January that they had decided to discontinue INNA, a green hydrogen and green ammonia project, to focus on their renewable energy portfolio instead. A detailed technical analysis by ESO last year revealed that INNA would cause severe, irreversible damage to the dark skies of Paranal and to the capacity of its facilities to operate as designed. The most significant impacts, affecting facilities such as the Very Large Telescope (VLT), the VLT Interferometer (VLTI), the Extremely Large Telescope (ELT), and CTAO-South, would be caused by light pollution, micro-vibrations, dust, and an increase of the air turbulence in the area.

“As we have said before, ESO and its Member States are fullysupportive of energy decarbonisation and initiatives that ensure a more prosperous and sustainable future. Green-energy projects — and other industrial projects that drive national and regional development — are fully compatible with astronomical observatories, if the differentfacilities are located at sufficient distances from one another,” says Barcons.

The INNA case and its proposed location highlight the urgent need to establish clear protection measures in the areas around astronomical observatories. Such measures are essential to allow astronomical observatories to continue operating, particularly in a region widely regarded as the best in the world for optical astronomy facilities, owing to the exceptional darkness of the skies over northern Chile.

“We will continue to work in close collaboration with local, regional, and national authorities to protect the dark skies of northern Chile, an irreplaceable natural heritage that is essential for advancing our understanding of the Universe and to enable world-class astronomy for the benefit of Chile and the global scientific community,” says Itziar de Gregorio-Monsalvo, ESO’s Representative in Chile.

“It has been incredibly reassuring to see so many people in Chile and around the world care deeply about, and actively speak up for, the protection of dark and quiet skies in the context of the INNA project,” says Barcons. “We are sincerely grateful for this engagement and solidarity. It gives us confidence that, by working together, we can continue to protect dark and quiet skies in Chile and elsewhere — for astronomy research and for humankind.” Since the project was submitted to SEA in December 2024, members of the astronomy community in Chile, in ESO’s Member States and beyond, political leaders and authorities at international, national, regional and local level, as well as countless members of the public, have made their voices heard in support of this shared goal.

ESO will continue to intensify its efforts to ensure that the pristine skies of Paranal remain the world’s best window to observe the Universe, and is also committed to the broader fight against light pollution and satellite interference, helping secure the natural heritage of dark and quiet skies around the world for future generations.

Source: ESP/News

---

More information

AES Andes announced that it will step back from the megaproject INNA, planned to be located The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, Czechia, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal, ESO will host and operate the south array of the Cherenkov Telescope Array Observatory, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.

---

Links

• Executive summary of ESO technical analysis on the impact of the INNA project
• Photos of Paranal


• INNA infographics


• Previous press releases on INNA: January 2025; March 2025

---

Contacts:

Francisco Rodríguez
Head of ESO Communications Chile
Santiago, Chile
Tel: +56 2 2463 3151
Email: francisco.rodriguez@eso.org

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

Connect with ESO on social media

---

Testing Einstein’s theory of relativity with the clearest gravitational-wave signal yet

Visualization of a binary black hole ringdown consistent with the gravitational-wave event GW250114.The gravitational waves are separated into two modes of the ringing remnant black hole, identified in the observation: the fundamental mode (green) and its first overtone (red). It also shows a predicted third tone (yellow) that the data places limits on. Visualization performed at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute), based on a numerical relativity simulation of the Simulating Extreme Spacetimes (SXS) Project. Credit: H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), K. Mitman (Cornell University)

Ringing Black Hole Animation (GW250114)
Credit: H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), K. Mitman (Cornell University)

---

To the point:

• Relativity put to the test: Relativity put to the test: A LIGO-Virgo-KAGRA team has conducted some of the most precise tests of Einstein’s theory of general relativity. The results were published in Physical Review Letters today.


• Einstein holds fast: In all tests, the observations match the theory’s predictions. In some cases, the tests based on this signal alone are two to three times more stringent than those obtained by combining data from dozens of other signals.


• The clearest signal: The team used data from GW250114, the strongest gravitational-wave signal ever detected from the merger of two black holes.


• Like a bell: For the first time, detailed analyses of the complete signal and the ringdown phase, which occurs shortly after the merger, have identified or constrained three gravitational-wave tones.

---

An international team, with key contributions from AEI researchers, identified three gravitational-wave tones in GW250114 for the first time and conducted the most stringent tests of general relativity.

Relativity put to the test

A year ago, almost to the day, the LIGO-Virgo-KAGRA collaboration observed by far the clearest gravitational-wave signal seen to date. GW250114 came from a coalescence of black holes with masses between 30 to 40 times that of our Sun about 1.3 billion light-years away.

“This signal has already proven to be a great boon for a test of the nature of black holes and of Hawking’s area law,” says Alessandra Buonanno, director of the Astrophysical and Cosmological Relativity department at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) in the Potsdam Science Park. “Now we have gone one step further and published some of the most stringent limits on deviations from Einstein’s theory of general relativity using GW250114.”

Additional analysis of the GW250114 data was published today in Physical Review Letters. The writing team included several AEI members: Alessandra Buonanno, who served as chair, and Lorenzo Pompili, Elisa Maggio, and Elise Sänger, who conducted several of the analyses reported in the publication.

Because GW250114 was observed so clearly, it can be compared in much greater detail to predictions from Einstein’s theory of relativity than other signals. This makes it possible to test whether general relativity holds true in the extreme conditions of a black hole coalescence, where strong gravitational fields meet rapidly changing dynamics. Any deviations from the predictions of general relativity could hint at new physics beyond Einstein’s theory.

Like a struck bell

The international research team obtained some of the key results using a method known as black hole spectroscopy. For this, the team focused on the ringdown of the GW250114 signal – the phase when the black hole settles into its final state right after the merger – and the characteristic spectrum of gravitational-wave modes, or tones, emitted during this phase. These tones resemble the sounds a bell makes when struck: Each tone is described by two numbers: its frequency and the rate at which it is fading. Measuring the spectrum of the tones and their fading times is called black hole spectroscopy.

For the first time, a triad of gravitational-wave tones

For the first time, researchers at the AEI in Potsdam found a third tone in the signal’s ringdown phase using a new data analysis tool they developed.

“Our analysis tool, originally proposed in 2018, takes into account the complete black-hole coalescence and makes no prior assumptions about the tones emitted during the ringdown phase,” explains Elisa Maggio, a former Marie Curie Fellow in the Astrophysical and Cosmological Relativity department and now an INFN Researcher in Rome, Italy. Maggio and Pompili collaborated on developing the most recent version of the tool and conducting the analysis. “By incorporating information from the entire signal, we constrained a higher-pitched tone at approximately twice the fundamental frequency for the first time, once again matching theoretical predictions.”

Together, the two tests – one looking at the ringdown alone and the other considering the full signal – complement each other. Once again, they empirically vindicate the rotating black hole solution discovered in 1963 by Roy Kerr.

One signal beats dozens of others

The research team also examined an earlier phase of the clearly observed black hole coalescence when the two black holes were orbiting each other more slowly.

“We used a flexible, theory-independent method developed earlier at the AEI to determine how much the gravitational-wave signal deviated from the predictions of general relativity early in the coalescence,” says Elise Sänger, a PhD student in the Astrophysical and Cosmological Relativity department who conducted the analysis. “Remarkably, using data from this one clearly observed signal alone allows us to set some of the most stringent constraints on possible deviations from general relativity.”

The constraints derived using the AEI-developed model are two to three times more stringent than those obtained by combining data from dozens of signals in the latest fourth Gravitational-Wave Transient Catalogue (GWTC-4.0).

Only the beginning

“These results demonstrate the great scientific value of accurate waveform models and ophisticated data analysis techniques,” says Alessandra Buonanno. “But this is only the beginning. Future observing runs will allow us to detect signals like GW250114 more frequently and more clearly. Each one will open new avenues for testing Einstein’s theory and searching for new physics.”

Source: Max Planck Institute for Gravitational Physics/News

---

Media contact:

Dr. Elke Müller
Press Officer AEI Potsdam, Scientific Coordinator
Tel: +49 331 567-7303
elke.mueller@aei.mpg.de

Science contacts:

Prof. Dr. Alessandra Buonanno
Director | LSC
Principal Investigator
Tel: +49 331 567-7220
Fax: +49 331 567-7298
alessandra.buonanno@aei.mpg.de
Homepage of Alessandra Buonanno

Dr. Elisa Maggio
INFN Researcher
elisa.maggio@aei.mpg.de
Istituto Nazionale di Fisica Nucleare, Rome

Dr. Lorenzo Pompili
Research Fellow
Lorenzo.Pompili@nottingham.ac.uk
University of Nottingham, School of Mathematical Sciences

Elise Sänger
PhD Student
elise.saenger@aei.mpg.de

---

Publication

The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration; Abac, A.; Abouelfettouh, I.; Acernese, F.; Ackley, K.; Adhicary, S.; Adhikari, D.; Adhikari, N. et al.

Black Hole Spectroscopy and Tests of General Relativity with GW250114. Physical Review Letters 136, 041403 (2026)

MPG.PuRe - DOI - pre-print - publisher-version

---

Further information

LIGO Science Summary
of the publication “Black hole spectroscopy and tests of general relativity with GW250114”

MPG.PuRe - DOI - pre-print - publisher-version

more

Ten years of gravitational-wave astronomy and the clearest signal yet

September 10, 2025
The LIGO-Virgo-KAGRA collaboration and the Max Planck Institute for Gravitational Physics celebrate the anniversary and present new, exciting results.

more

LIGO-Virgo-KAGRA Collaboration successfully wraps up its fourth Observing Run

November 19, 2025
Further exciting results anticipated from O4’s remaining parts

more

Doubling the gravitational-wave transient catalogue

August 26, 2025

LIGO-Virgo-KAGRA researchers at the Max Planck Institute for Gravitational Physics and at Leibniz University Hannover make significant contributions to detect and analyze new gravitational-wave candidates

more

Brito, R.; Buonanno, A.; Raymond, V.
Black-hole Spectroscopy by Making Full Use of Gravitational-Wave Modeling. Physical Review D 98 (8), 084038 (2018)

MPG.PuRe - DOI - pre-print

---