Hubble sees asteroids colliding at nearby star for first time

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Fomalhaut cs1 and cs2 (annotated)

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Fomalhaut cs1 and cs2 (clean image)

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Fomalhaut cs2 (artist’s concept)

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Videos


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Fomalhaut cs2 (artist’s concept animation)


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Space Sparks episode 21: Hubble sees asteroids colliding at nearby star for first time

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In a historical milestone, catastrophic collisions in a nearby planetary system were witnessed for the first time by astronomers using the NASA/ESA Hubble Space Telescope. As they observed the bright star Fomalhaut, the scientists saw the impact of massive objects around the star. The Fomalhaut system appears to be in a dynamical upheaval, similar to what our solar system experienced in its first few hundred million years after formation.

“This is certainly the first time I’ve ever seen a point of light appear out of nowhere in an exoplanetary system,” said principal investigator Paul Kalas of the University of California, Berkeley. “It’s absent in all of our previous Hubble images, which means that we just witnessed a violent collision between two massive objects and a huge debris cloud unlike anything in our own solar system today. Amazing!"

Just 25 light-years from Earth, Fomalhaut is one of the brightest stars in the night sky. Located in the constellation Piscis Austrinus, also known as the Southern Fish, it is more massive and brighter than the Sun and is encircled by several belts of dusty debris.

In 2008, scientists used Hubble to discover a candidate planet around Fomalhaut, making it the first stellar system with a possible planet found using visible light. That object, called Fomalhaut b, now appears to be a dust cloud masquerading as a planet – the result of colliding planetesimals. While searching for Fomalhaut b in recent Hubble observations, scientists were surprised to find a second point of light at a similar location around the star. They call this object “circumstellar source 2” or “cs2” while the first object is now known as “cs1.”

Tackling mysteries of colliding planetesimals

Why astronomers are seeing both of these debris clouds so physically close to each other is a mystery. If the collisions between asteroids and planetesimals were random, cs1 and cs2 should appear by chance at unrelated locations. Yet, they are positioned intriguingly near each other along the inner portion of Fomalhaut’s outer debris disk.

Another mystery is why scientists have witnessed these two events within such a short timeframe. “Previous theory suggested that there should be one collision every 100,000 years, or longer. Here, in 20 years, we've seen two,” explained Kalas. “If you had a movie of the last 3,000 years, and it was sped up so that every year was a fraction of a second, imagine how many flashes you'd see over that time. Fomalhaut’s planetary system would be sparkling with these collisions.”

Collisions are fundamental to the evolution of planetary systems, but they are rare and difficult to study.

“The exciting aspect of this observation is that it allows researchers to estimate both the size of the colliding bodies and how many of them there are in the disk, information which is almost impossible to get by any other means,” said co-author Mark Wyatt at the University of Cambridge in England. “Our estimates put the planetesimals that were destroyed to create cs1 and cs2 at just 30 kilometres in size, and we infer that there are 300 million such objects orbiting in the Fomalhaut system.”

“The system is a natural laboratory to probe how planetesimals behave when undergoing collisions, which in turn tells us about what they are made of and how they formed,” explained Wyatt.

Cautionary tale

The transient nature of Fomalhaut cs1 and cs2 poses challenges for future space missions aiming to directly image exoplanets. Such telescopes may mistake dust clouds like cs1 and cs2 for actual planets.

“Fomalhaut cs2 looks exactly like an extrasolar planet reflecting starlight,” said Kalas. “What we learned from studying cs1 is that a large dust cloud can masquerade as a planet for many years. This is a cautionary note for future missions that aim to detect extrasolar planets in reflected light."

Looking to the future

Kalas and his team have been granted Hubble time to monitor cs2 over the next three years. They want to see how it evolves -- does it fade, or does it get brighter? Being closer to the dust belt than cs1, the expanding cs2 cloud is more likely to start encountering other material in the belt. This could lead to a sudden avalanche of more dust in the system, which could cause the whole surrounding area to get brighter.

“We will be tracing cs2 for any changes in its shape, brightness, and orbit over time,” said Kalas, “It’s possible that cs2 will start becoming more oval or cometary in shape as the dust grains are pushed outward by the pressure of starlight.” The team also will use the NIRCam (Near-Infrared Camera) instrument on the NASA/ESA/CSA James Webb Space Telescope to observe cs2. Webb’s NIRCam has the ability to provide color information that can reveal the size of the cloud’s dust grains and their composition. It can even determine if the cloud contains water ice.

Hubble and Webb are the only observatories capable of this kind of imaging. While Hubble primarily sees in visible wavelengths, Webb could view cs2 in the infrared. These different, complementary wavelengths are needed to provide a broad multi-spectral investigation and a more complete picture of the mysterious Fomalhaut system and its rapid evolution.

This research appears today in the December 18 issue of Science.

Source: ESA/Hubble/News

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More information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Image Credit: NASA, ESA, P. Kalas (UC Berkeley), J. DePasquale (STScI)

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Links

• Release on ESA website
• Release on NASA website
• Science paper

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Contacts:

Bethany Downer
ESA/Hubble Chief Science Communications Officer
Email: Bethany.Downer@esahubble.org

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A neighbouring vista of stellar birth

LMC N159

A field filled with stars and covered by clouds of gas and dust. In the centre, a thick column of dark black dust blocks light from stars that light it up from behind. More clouds behind those stars are illuminated in pale colours. Complex, layered filaments of red dust lie to the left and right. Blue, white and gold stars in various sizes can be seen around, within and through the colourful layers of dust. Credit: ESA/Hubble & NASA, R. Indebetouw

Today’s ESA/Hubble Picture of the Week highlights another view of a distant stellar birthplace. Captured in a parallel field to a recently released image, this scene reveals a neighbouring region of the N159 star-forming complex in the Large Magellanic Cloud, approximately 160 000 light-years away.

Thick clouds of cold hydrogen gas dominate the scene, forming a complex network of ridges, cavities, and glowing filaments. Embedded within these dense clouds, newly formed stars begin to shine, their intense radiation causing the surrounding hydrogen to glow in deep red tones.

The brightest regions mark the presence of hot, massive young stars whose powerful stellar winds and energetic light reshape their environment. These forces carve out bubble-like structures and hollowed cavities in the gas, clear signatures of stellar feedback in action. Dark clouds in the foreground are lit from behind by new stars. Together, the glowing clouds and sculpted bubbles reveal a dynamic interplay between star formation and the material from which stars are born, capturing the ongoing cycle of creation and transformation within this neighbouring galactic system.

N159 is one of the most massive star-forming clouds in the Large Magellanic Cloud, a dwarf galaxy that is the largest of the small galaxies that orbit the Milky Way. This image shows just a portion of this expansive star-forming complex, as the entire complex stretches over 150 light-years across.

Links

• Pan: N159

Source: ESA/Hubble/potw

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NASA IXPE’s Longest Observation Solves Black Hole Jets Mystery

Two composite images show side-by-side observations of the Perseus Cluster from NASA’s IXPE (Imaging X-Ray Polarimetry Explorer) and Chandra X-ray Observatory. Scientists used data from both observatories, along with data from Nuclear Spectroscopic Telescope Array (NuSTAR), and Neil Gehrels Swift Observatory, to confirm measurements of the galaxy cluster.Credit: X-ray: (Chandra) NASA/CXC/SAO, (IXPE) NASA/MSFC; Image Processing: NASA/CXC/SAO/N. Wolk and K. Arcand

Chandra & IXPE composite image of the Perseus Cluster.
X-ray: (Chandra) NASA/CXC/SAO, (IXPE) NASA/MSFC; Image Processing: NASA/CXC/SAO/N. Wolk and K. Arcand

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An international team of astronomers using NASA’s IXPE (Imaging X-ray Polarimetry Explorer) has identified the origin of X-rays in a supermassive black hole’s jet, answering a question that has been unresolved since the earliest days of X-ray astronomy. Their findings are described in a paper published in The Astrophysical Journal Letters, by the American Astronomical Society, Nov. 11.

The IXPE mission observed the Perseus Cluster, the brightest galaxy cluster observable in X-rays, for more than 600 hours over a 60-day period between January and March. Not only is this IXPE’s longest observation of a single target to date, it also marks IXPE’s first time observing a galaxy cluster.

Specifically, the team of scientists studied the polarization properties of 3C 84, the massive active galaxy located at the very center of the Perseus Cluster. This active galaxy is a well-known X-ray source and a common target for X-ray astronomers because of its proximity and brightness.

Because the Perseus Cluster is so massive, it hosts an enormous reservoir of X-ray emitting gas as hot as the core of the Sun. The use of multiple X-ray telescopes, particularly the high-resolution imaging power of NASA’s Chandra X-ray Observatory was essential to disentangle the signals in the IXPE data. Scientists combined these X-ray measurements with data from the agency’s Nuclear Spectroscopic Telescope Array (NuSTAR) mission and Neil Gehrels Swift Observatory.

Fast facts:

• Polarization measurements from IXPE carry information about the orientation and alignment of emitted X-ray light waves. The more X-ray waves traveling in sync, the higher the degree of polarization.


• X-rays from an active galaxy like 3C 84 are thought to originate from a process known as inverse Compton scattering, where light bounces off particles and gains energy. The polarization measurements from IXPE allow us to identify the presence of either inverse Compton scattering or other scenarios.


• “Seed photons” is the term for the lower-energy radiation undergoing the energizing process of inverse Compton scattering.


• You may remember the Perseus Cluster from this sonification replicating what a Black Hole sounds like from May 2022.

“While measuring the polarization of 3C 84 was one of the key science goals, we are still searching for additional polarization signals in this galaxy cluster that could be signatures of more exotic physics,” said Steven Ehlert, project scientist for IXPE and astronomer at NASA’s Marshall Space Flight Center in Huntsville.

“We’ve already determined that for sources like 3C 84, the X-rays originated from inverse Compton scattering,” said Ioannis Liodakis, a researcher at the Institute of Astrophysics – FORTH in Heraklion, Greece, and lead author on the paper. “With IXPE observations of 3C 84 we had a unique chance to determine the properties of the seed photons.”

The first possible origin scenario for the seed photons is known as synchrotron self-Compton, where lower-energy radiation originates from the same jet that produces the highly energetic particles.

In the alternative scenario known as external Compton, seed photons originate from background radiation sources unrelated to the jet.

“The synchrotron self-Compton and external Compton scenarios have very different predictions for their X-ray polarization,” said Frederic Marin, an astrophysicist at the Strasbourg Astronomical Observatory in France and co-author of the study. “Any detection of X-ray polarization from 3C 84 almost decisively rules out the possibility of external Compton as the emission mechanism.”

Throughout the 60-day observation campaign, optical and radio telescopes around the world turned their attention to 3C 84 to further test between the two scenarios.

NASA’s IXPE measured a net polarization of 4% in the X-rays spectrum, with comparable values measured in the optical and radio data. These results strongly favor the synchrotron self-Compton model for the seed photons, where they come from the same jet as the higher-energy particles.

“Separating these two components was essential to this measurement and could not be done by any single X-ray telescope, but by combining the IXPE polarization data with Chandra, NuSTAR, and Swift, we were able to confirm this polarization measurement was associated specifically with 3C 84,” said Sudip Chakraborty, a researcher at the Science and Technology Institute of the Universities Space Research Association in Huntsville, Alabama, and co-author on the paper.

Scientists will continue to analyze IXPE’s data from different locations in the Perseus Cluster for different signals.

Written by Michael Allen

Source: NASA/Mission Ipex

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More about IXPE

NASA’s IXPE, which continues to provide unprecedented data enabling groundbreaking discoveries about celestial objects across the universe, is a joint NASA and Italian Space Agency mission with partners and science collaborators in 12 countries. The IXPE mission is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. BAE Systems, Inc., headquartered in Falls Church, Virginia, manages spacecraft operations together with the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder.

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Holiday Collection: Cosmic Holiday Greetings From NASA's Chandra X-ray Observatory

NGC 4782/NGC 4783,NGC 2264, The Christmas Tree Nebula,NGC 6357/Pismis 24 and M78
Four images with Chandra data that are connected to the winter season, labeled.
Credit: NASA/CXC/SAO

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A Quick Look: Cosmic Holiday Greetings From NASA's Chandra X-ray Observatory - More Videos

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NASA’s Chandra X-ray Observatory is sending out a holiday card with four new images of cosmic wonders. Each of the quartet of objects evokes the winter season or one of its celebratory days either in its name or shape.

Chandra’s seasonal greetings begin with NGC 4782 and NGC 4783, a pair of colliding galaxies when oriented in a certain way resembles a snowman. The top and bottom of the snowman are each elliptical galaxies, separated by a distance of about 170 million light-years. The galaxies, seen in an image from NASA’s Hubble Space Telescope (gray), are bound together through gravity. X-rays from Chandra (purple) show a bridge of hot gas between the two galaxies, like a winter scarf.

Four images with Chandra data that are connected to the winter season, labeled.

Credit: NASA/CXC/SAOTo the right of the cosmic snowman is one of the most iconic symbols of the season, a Christmas tree. This celestial version takes an optical light image (red, gold, blue, and white) from an astrophotographer that shows the “branches” of NGC 2264, a relatively young nebula where new stars are forming. Within this cloud of gas and dust, baby stars appear as high-energy baubles in X-ray light from Chandra (red, green, and blue) plus some additional X-ray data from ESA’s XMM-Newton.

To the right of the cosmic snowman is one of the most iconic symbols of the season, a Christmas tree. This celestial version takes an optical light image (red, gold, blue, and white) from an astrophotographer that shows the “branches” of NGC 2264, a relatively young nebula where new stars are forming. Within this cloud of gas and dust, baby stars appear as high-energy baubles in X-ray light from Chandra (red, green, and blue) plus some additional X-ray data from ESA’s XMM-Newton.

NGC 2264, The Christmas Tree Nebula, in "twinkling" light.

Credit: X-ray: NASA/CXC/SAO and ESA/XMM-Newton; Optical: B. Vuk;

Image Processing: NASA/CXC/SAO/L. Frattare and K. Arcand

 

On the bottom left is the nebula NGC 6357 that contains Pismis 24, a young cluster of stars about 5,500 light-years from Earth. This stellar landscape is reminiscent of a winter vista in a view from NASA’s James Webb Space Telescope (red, green, and blue). Chandra data (red, green and blue) punctuate the scene with bursts of colored lights representing high-energy activity from the active stars.

The final image in this holiday card display is M78, a striking nebula in the Orion constellation that may also bring a partridge in the proverbial pear tree to mind. M78 is a reflection nebula, which is cloud interstellar dust that glows from the scattered light embedded within it. The bird-like structure is seen in infrared and optical light by Euclid (red, green and blue) while Chandra data provide speckled lights across the nebula (red, green, and blue).

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.

Source: NASA’s Chandra X-ray Observatory

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Visual Description:

This release features four colorful composite images presented in an irregular grid, each evoking an aspect of winter and the holiday season.

The first image, at our upper left, features a pair of colliding galaxies that resembles a snowman in optical light from Hubble when oriented vertically. The two galaxies, NGC 4782 and NGC 4783, appear as hazy white balls with solid white cores, one stacked above the other. Linking the two galaxies is a bridge of hot gas in X-ray light from Chandra depicted here as a string of fuzzy neon purple balls. The string of gas loosely zigzags back and forth between the two galaxies, like a cozy scarf worn by a snowman.

The second holiday image, at the upper right of the irregular grid, strongly resembles a golden Christmas tree bedecked with twinkling lights. The tree is actually NGC 2264, a relatively young nebula where new stars are forming. The tree's branches, which sweep back and forth in a roughly conical shape, are golden clouds of dust and gas, all from optical light captured by an astrophotographer. Tucked into these branches are colorful lights and glowing baubles in X-rays from Chandra and XMM-Newton, colored in green, blue, purple, and orange; baby stars growing inside the nebula.

At the lower lefthand corner of the grid is a winter scene fit for a holiday greeting card. Above what appears to be a fantastical snowy mountainscape, is a brilliant blue sky packed with colorful lights. The golden mountainscape is in fact part of the nebula NGC 6357, as captured by NASA's James Webb Space Telescope. The green, red, and golden lights in the blue sky above are bursts of high-energy X-rays from active stars, detected by Chandra.

The final holiday image, at the lower right of the grid, is a nebula which calls to mind the first gift in the Christmas carol 'The Twelve Days of Christmas'. Here, the wispy burnt orange nebula, M78, forms a tree, with a vertical trunk near the center of the image in infrared and optical light from the European Space Agency's Euclid mission. The tree's bushy branches reach toward our upper left, and its tail of roots drifts toward our lower right. The tree of interstellar dust is offset by a pink c,brloud, which resembles cotton candy, and is backed by a black sky packed with speckled lights. At the top of the tree, near the upper lefthand corner of the image, is a dusty orange cloud shape which strongly resembles a bird in profile; the proverbial pa,hrrtridge in the pear tree. Sprinkled across are tiny dots of colorful lights,showcasing X-rays captured by Chandra.

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Fast Facts for NGC 4782/NGC 4783, The Snowman Galaxies:

Credit: X-ray: NASA/CXC/SAO; Optical: NASA/ESA/STScI/HST; Image Processing: NASA/CXC/SAO/J. Schmidt
Release Date: December 22, 2025
Scale: Image is about 1.4 arcmin (87,000 light-years) across.
Category: Groups and Clusters of Galaxies
Coordinates (J2000): RA: 12h 54m 35.6s | Dec: -12° 34' 07.4"
Constellation: Corvus
Observation Date(s): 1 observation June 16, 2002
Observation Time: 13 hours and 47 minutes
Obs. IDs: 3220
Instrument: ACIS
References: Machacek, M., et al., 2007, ApJ, 664, 804
Color Code: X-ray: purple; Optical: grayscale
Distance Estimate: About 210 million light-years from Earth

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Fast Facts for NGC 2264, The Christmas Tree Nebula:

Credit: X-ray: NASA/CXC/SAO and ESA/XMM-Newton; Optical: B. Vuk; Image Processing: NASA/CXC/SAO/L. Frattare and K. Arcand
Release Date: December 22, 2025
Scale: Image is about 77 arcmin (56 light-years) across.
Category: Normal Stars & Star Clusters
Coordinates (J2000): RA: 06h 40m 42.8s | Dec: +09° 49' 03.6"
Constellation: Monoceros
Observation Date(s): 8 observations from February 2002 to December 2011
Observation Time: 137 hours 26 minutes (5 days 17 hours 26 minutes)
Obs. IDs: 2540, 2550, 9768, 9769, 13610, 13611, 14368, 14369
Instrument: ACIS
References: Ramirez, S., et al., 2004, AJ, 127, 2659
Instrument: ACIS
Color Code: X-ray: red, green, and blue; Optical: red, gold, blue, and white
Distance Estimate: About 2,500 light-years from Earth

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Fast Facts for NGC 6357/Pismis 24:

Credit: X-ray: NASA/CXC/Penn State/G.Garmire; Infrared: NASA, ESA, CSA, and STScI; Image Processing: NASA/CXC/SAO/L. Frattare and NSA/ESA/CSA/STScI/A. Pagan
Release Date: December 22, 2025
Scale: Image is about 4.2 arcmin (6.7 light-years) across.
Category: Normal Stars and Star Clusters
Coordinates (J2000): RA: 17h 24m 44.4s | Dec: -34° 11' 35.9"
Constellation: Scorpius
Observation Date(s): 3 observations from July 2004 to Aug 2022
Observation Time: 30 hours 15 minutes (1 day 6 hours 15 minutes)
Obs. IDs: 4477, 18453, 26003
Instrument: ACIS
References: Townsley, L., et al., 2019, ApJS, 244, 28
Color Code: X-ray: red, green, and blue; Infrared: red, green, and blue
Distance Estimate: About 5,500 light-years from Earth

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Fast Facts for M78:

Credit: X-ray: NASA/CXC/SAO; Infrared/Optical: ESA/Euclid/Euclid Consortium/NASA; Image Processing: NASA/CXC/SAO/L. Frattare
Release Date: December 22, 2025
Scale: Image is about 41 arcmin (19 light-years) across.
Category: Normal Stars and Star Clusters
Coordinates (J2000): RA: 5h 46m 45.8s | Dec: +0° 0′ 08.1"
Constellation: Orion
Observation Date(s): 2 observations: Oct 2000 and Aug 2021
Observation Time: 28 hours 56 minutes (1 day 4 hours 56 minutes)
Obs. IDs: 1872, 25686
Instrument: ACIS
References: Grosso, N et al., 2004, A&A, 419, 653
Color Code: X-ray: red, green, and blue; Infrared/Optical: red, green, and blue
Distance Estimate: About 1,600 light-years from Earth

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Astronomers challenge 50-year-old quasar law

An artist’s impression of a bright quasar almost outshining its host galaxy. Credit: Dimitrios Sakkas (tomakti), Antonis Georgakakis, Angel Ruiz, Maria Chira (NOA)

Licence type: Attribution (CC BY 4.0)

Compelling evidence that the structure of matter surrounding supermassive black holes has changed over cosmic time has been uncovered by an international team of astronomers. If true, the research led by the National Observatory of Athens and published today in Monthly Notices of the Royal Astronomical Society would challenge a fundamental law which has existed for almost five decades.

Quasars – first identified in the 1960s – are some of the brightest objects in the universe. They are powered by supermassive black holes as matter, pulled by strong gravity, spirals inwards, forming a rotating disc-like structure which eventually plunges into the black hole.

This disc is extremely hot because of the friction between matter particles as they revolve around the black hole. It produces 100 to 1,000 times as much light as an entire galaxy containing 100 billion stars, generating a glow that outshines its host galaxy and everything in it. This vast amount of ultraviolet light can be observed by telescopes, allowing astronomers to find quasars at the edge of the universe.

The ultraviolet light of the disc is also believed to be the fuel for the much more energetic X-ray light produced by quasars: the ultraviolet light rays as they travel through space intercept clouds of highly energetic particles very close to the black hole, a structure also known as the “corona”.

As they bounce off these energetic particles, the ultraviolet rays are boosted in energy and generate intense X-ray light that our detectors can also spot.

eROSITA real image of a region of the X-ray sky centered at one of the quasars used in the new research. Credit: Angel Ruiz (NOA) based on maps created by Jeremy Sanders (MPE)

Licence type: Attribution (CC BY 4.0)

Because of their shared history, the X-ray and ultraviolet emissions of quasars are tightly connected – brighter ultraviolet light typically means stronger X-ray intensity. This correlation, discovered nearly 50 years ago, provides fundamental insights into the geometry and physical conditions of the material close to supermassive black holes and has been the focus of intense research for decades.

The latest research adds a new twist to previous studies by challenging the universality of the correlation – a fundamental assumption that implies that the structure of matter around black holes is similar throughout the universe.

It shows that when the universe was younger – about half its present age – the correlation between the X-ray and ultraviolet light of quasars was significantly different from that observed in the nearby universe. The discovery suggests that the physical processes linking the accretion disc and the corona around supermassive black holes may have changed over the last 6.5 billions of years of cosmic history.

“Confirming a non-universal X-ray-to-ultraviolet relation with cosmic time is quite surprising and challenges our understanding of how supermassive black holes grow and radiate,” said Dr Antonis Georgakakis, one of the study’s authors.

“We tested the result using different approaches, but it appears to be persistent.”

The study combines new X-ray observations from eROSITA X-ray telescope and archival data from the XMM-Newton X-ray observatory of the European Space Agency to explore the relation between X-ray and ultraviolet light intensity of an unprecedentedly large sample of quasars. The new eROSITA’s wide and uniform X-ray coverage proved decisive, enabling the team to study quasar populations on a scale never before possible.

An artist’s impression of matter spiralling inwards, pulled by the strong gravity of a central supermassive black hole, forming an “accretion disk”. Friction heats the infalling material to high temperatures producing intense ultraviolet light. This is reprocessed by hot plasma (extremely high temperature matter) believed to exist very close to the black hole — the “corona” — to produce energetic X-ray light. Credit: Dimitrios Sakkas (tomakti), Antonis Georgakakis, Angel Ruiz, Maria Chira (NOA)

Licence type: Attribution (CC BY 4.0)

The universality of the UV-to-X-ray relation underpins certain methods that use quasars as "standard candles" to measure the geometry of the universe and ultimately probe the nature of dark matter and dark energy. This new result highlights the necessity for caution, demonstrating that the assumption of unchanging black hole structure across cosmic time must be rigorously re-examined.

“The key advance here is methodological,” said postdoctoral researcher Maria Chira, of the National Observatory of Athens, who is the paper’s lead author.

“The eROSITA survey is vast but relatively shallow – many quasars are detected with only a few X-ray photons. By combining these data in a robust Bayesian statistical framework, we could uncover subtle trends that would otherwise remain hidden.”

The full set of eROSITA all-sky scans will soon allow astronomers to probe even fainter and more distant quasars. Future analyses using these data – together with next-generation X-ray and multiwavelength surveys – will help reveal whether the observed evolution reflects a genuine physical change or simply selection effects.

Such studies will bring new insight into how supermassive black holes power the most luminous objects in the universe, and how their behaviour has evolved over cosmic time.

Source: Royal Astronomical Society (RAS)/Research Highlights

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Media contacts:

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

Dr Robert Massey
Royal Astronomical Society
Mob: +44 (0)7802 877 699
press@ras.ac.uk

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Science contacts:

Maria Chira
National Observatory of Athens
mchira@noa.gr

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Further information

The paper ‘Revisiting the X-ray–to–UV relation of Quasars in the era of all-sky surveys’ by Maria Chira et al. has been published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/staf1551.

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Notes for editors

About the Royal Astronomical Society

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

The RAS organises scientific meetings, publishes international research 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.

Submitted by Sam Tonkin on Thu, 11/12/2025 - 08:00

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Super Massive Black Holes May Be Picky Eaters

High-resolution ALMA image of the molecular gas, as traced by emission from the carbon monoxide molecule, for four merging galaxies hosting dual AGN. We can clearly see large concentrated reservoirs of molecular gas. Credit: ALMA (ESO/NAOJ/NRAO)/ M. Johnstone et al. / CATA / J. Utreras

Schematic representation of the amount of gas available to feed supermassive black holes during a major galaxy merger.
Credits: CATA/J. Utreras, M. Johnston

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New ALMA research reveals galaxy mergers that feed black holes may not be the buffet astronomers previously thought

Black holes are notorious for gobbling up everything that comes their way. Still, astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered that even supermassive black holes can be picky eaters, which can significantly impact their growth. An international team of astronomers led by Makoto A. Johnstone, a PhD candidate with the University of Virginia, made this discovery. The team used ALMA to study seven nearby galaxy mergers hosting supermassive black holes separated by only a few thousand light-years.

When two massive, gas-rich galaxies merge, gravity drives vast amounts of cold molecular gas toward the centers of both systems, where supermassive black holes (SMBHs) reside. These brief, turbulent phases can light up one or both black holes as active galactic nuclei (AGN), making them some of the most energetic objects in the universe. Yet, puzzlingly, not all merging galaxies host two actively feeding black holes; some show only one, while others seem to have no appetite.

These observations revealed a dense, chaotic pile of gas clouds around many black holes (especially the more massive ones), suggesting that mergers are highly effective at delivering fuel for growth directly to their doorsteps. Yet the current brightness of the black holes (a measure of how rapidly they are accreting) does not increase with the amount of available gas. Even with plenty of food nearby, most SMBHs are nibbling rather than gorging, suggesting that black hole growth during mergers could be highly inefficient, with an inconsistent digestion of gas on short timescales. “The inefficiency of the observed supermassive black hole growth, even when dense reservoirs of molecular gas are present, raises questions about the physical conditions necessary to trigger these growth episodes,” said Makoto. “In addition to occurring in extreme dusty environments, the AGN activity is likely highly variable and episodic, explaining why it has been so difficult to detect two simultaneously active black holes in mergers.”

The team compared systems with both black holes active (dual AGN) to mergers in which only one showed obvious activity (single AGN). In some of these single AGN cases, the black hole with no appetite truly seemed starved of cold gas, but in others, the gas was observed, but the black hole still refused to eat, possibly because it was observed between feedings. “These unique ALMA observations show how black holes are actively being fed during a major galaxy merger, an event that we strongly suspect is critical in setting up the observed connection between black hole growth and galaxy evolution. It is only now, thanks to the unique and revolutionary ALMA capabilities, that this study is feasible,” says Ezequiel Treister, principal investigator of this research project, and co-author of the study.

ALMA also finds that many active black holes are slightly offset from their main rotating gas disks, suggesting violent gravitational interactions that may have displaced the black holes during galaxy mergers. Together, these results show that in galaxy collisions, having enough energy to feed SMBHs is only half the story; timing, turbulence, and dust decide when, and if, both black holes flare to life.

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

Scientific Paper

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Additonal Information

The results of this investigation appear in "Molecular Gas in Major Mergers Hosting Dual and Single AGNs at <10 kpc Nuclear Separations" by Makoto A. Johnstone et al. in the Astrophysical Journal.

This article is based on a press release from the National Radio Astronomical Observatory (NRAO), an ALMA partner on behalf of North America.

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

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

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Contacts:

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

Jill Malusky
Public Information Officer
NRAO
Phone: +1 304-456-2236
Email: jmalusky@nrao.edu

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

Yuichi Matsuda
Education and Public Outreach Officer
NAOJ
Email: yuichi.matsuda@nao.ac.jp

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“Superkilonova” A Star So Nice, It Explodes Twice

Artist interpretation depicts a hypothesized event known as a superkilonova. Initially, a massive star explodes in a supernova, which generates elements like carbon and iron (left). In the aftermath, two neutron stars are born, at least one of which is believed to be less massive than our Sun (middle). The neutron stars spiral together, sending gravitational waves rippling through the cosmos, before merging in a dramatic kilonova (right). Kilonovae seed the universe with the heaviest elements, such as gold at platinum, which glow in red light as depicted in the animation. Credit: Caltech/K. Miller and R. Hurt (IPAC)

Double Cosmic Explosion

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Potential first-of-a-kind may have produced gravitational waves and light

Maunakea, Hawaiʻi – A team of astronomers using a variety of telescopes, including the W. M. Keck Observatory on Maunakea, Hawaiʻi Island, have discovered a possible “Superkilonova” that exploded not once but twice, evidence that this oddball event may be a first-of-a-kind superkilonova, or a kilonova spurred by a supernova. Such an event has been hypothesized but never seen.

When the most massive stars reach the ends of their lives, they blow up in spectacular supernova explosions, which seed the universe with heavier elements such as carbon and iron. Another type of explosion—the kilonova—occurs when a pair of dense, dead stars called neutron stars smash together, forging even heavier elements, such as gold and uranium. The heavy elements created by both of these explosions are among the basic building blocks of stars and planets.

So far, only one kilonova has been unambiguously confirmed to date, a historic event known as GW170817, which took place in 2017. In that case, two neutron stars smashed together, sending ripples in space-time known as gravitational waves, as well as light waves, across the cosmos. The cosmic blast was detected in gravitational waves by the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO) and its European partner, the Virgo gravitational-wave detector, and in light waves by dozens of ground-based and space telescopes around the world.

The curious case of the kilonova candidate, AT2025ulz, is complex, and thought to have stemmed from a supernova blast that went off hours before, ultimately obscuring astronomers’ view and making the case more complicated.

“At first, for about three days, the eruption looked just like the first kilonova in 2017,” said Mansi Kasliwal, professor of astronomy at The California Institute of Technology and director of Palomar Observatory. “Everybody was intensely trying to observe and analyze it, but then it started to look more like a supernova, and some astronomers lost interest. Not us.”

The study, led by The California Institute of Technology, is published in The Astrophysical Journal Letters.

In August 2025, a new gravitational-wave signal was picked up by The Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo in Italy. Within minutes, an alert was issued to the astronomical community containing a rough map of the source signaling to researchers that gravitational waves had been registered from what appeared to be a merger between two objects, with at least one of them being unusually tiny.

After first being identified by the Zwicky Transient Facility at Palomar Observatory, Kasliwal coordinated with Keck Observatory staff astronomer Michael Lundquist to launch a rapid Target of Opportunity (ToO) observation of AT2025ulz, a process that allows scientists to request immediate access for short-lived cosmic events. Mansi’s ToO request enabled the immediate spectroscopic follow-up using the Low-Resolution Imaging Spectrograph (LRIS).

“Keck Observatory provided the imagery and spectroscopy via our Low-Resolution Imaging Spectrograph (LRIS) Instrument to measure the host extinction and redshift of the galaxy as well as looking at the spectroscopic evolution,” Lundquist said. “This highlights Keck Observatory’s Target of Opportunity capability to rapidly respond to transient alerts and deliver the spectroscopic data needed to explore potential multi-messenger associations.”

The observations confirmed that the eruption of light had faded fast and glowed at red wavelengths—just as GW170817 had done eight years earlier. In the case of the GW170817 kilonova, the red colors came from heavy elements like gold; these atoms have more electron energy levels than lighter elements, so they block blue light but let red light pass through.

Then, days after the blast, AT2025ulz started to brighten again, turn blue and show hydrogen in its spectra, all signs of a supernova not a kilonova (specifically a “stripped-envelope, core-collapse” supernova). Supernovae from distant galaxies are generally not expected to generate enough gravitational waves to be detectable by LIGO and Virgo, whereas kilonovae are. This led some astronomers to conclude that AT2025ulz was triggered by a typical, ho-hum supernova and not in fact related to the gravitational-wave signal.

What Might Be Going On?

Kasliwal says that several clues tipped her off that something unusual had taken place. Though AT2025ulz did not resemble the classic kilonova GW170817, it also did not look like an average supernova. Additionally, the LIGO–Virgo gravitational-wave data had revealed that at least one of the neutron stars in the merger was less massive than our Sun, a hint that one or two small neutron stars might have merged to produce a kilonova.

Neutron stars are the leftover remains of massive stars that explode as supernovae. They are thought to be around the size of San Francisco (about 22 to 30 kilometers across) with masses that range from 1.2 to about 3 times that of our Sun. Some theorists have proposed ways in which neutron stars might be even smaller, with masses less than the Sun’s, but none have been observed so far.

Theorists invoke two scenarios to explain how a neutron star could be that small. In one, a rapidly spinning massive star goes supernova, then splits into two tiny, sub-solar neutron stars in a process termed fission. In the second scenario, called fragmentation, the rapidly spinning star again goes supernova, but this time a disk of material forms around the collapsing star. The lumpy disk material coalesces into a tiny neutron in a manner similar to how planets form.

With LIGO and Virgo having detected at least one sub-solar neutron star, it is possible, according to theories proposed by co-author Brian Metzger of Columbia University that two newly formed neutron stars could have crashed into each other, erupting as a kilonova that sent gravitational waves rippling through the cosmos. As the kilonova churned out heavy metals, it would have initially glowed in red light as ZTF and other telescopes observed. The expanding debris from the initial supernova blast would have obscured the astronomers’ view of the kilonova. In other words, a supernova may have birthed twin baby neutron stars that then merged to make a kilonova.

“The only way theorists have come up with to birth sub-solar neutron stars is during the collapse of a very rapidly spinning star,” Metzger says. “If these ‘forbidden’ stars pair up and merge by emitting gravitational waves, it is possible that such an event would be accompanied by a supernova rather than be seen as a bare kilonova.”

But while this theory is tantalizing and interesting to consider, the research team stresses that there is not enough evidence to make firm claims. The only way to test the superkilonovae theory is to find more.

“Future kilonovae events may not look like GW170817 and may be mistaken for supernovae,” Kasliwal says. “We can look for new possibilities in data like this, but we do not know with certainty that we found a superkilonova. The event, nevertheless, is eye o,brpening.”

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Source: W. M. Keck Observatory/News

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About LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion.

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

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Bright Blue Cosmic Outbursts Likely Caused by Large Black Holes Shredding Massive Companions

PR Image noirlab2533a
Most luminous fast blue optical transient

PR Image noirlab2533b
Most luminous fast blue optical transient (collage)

PR Image noirlab2533c
Most luminous fast blue optical transient infographic

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Quickly-fading luminous blue outbursts were once thought to be unusual supernovae, but a new outburst, the brightest yet, suggests otherwise

In 2024, astronomers discovered the brightest Luminous Fast Blue Optical Transient (LFBOT) ever observed. LFBOTs are extremely bright flashes of blue light that shine for brief periods before fading away. New analysis of this record-breaking burst, which includes observations from the International Gemini Observatory, funded in part by the U.S. National Science Foundation, challenges all prior understanding of these rare explosive events.

Among the more puzzling cosmic phenomena discovered over the past few decades are brief and very bright flashes of blue and ultraviolet light that gradually fade away, leaving behind faint X-ray and radio emissions. This curious class of objects is known as luminous fast blue optical transients (LFBOTs), and with slightly more than a dozen discovered so far, astronomers have debated whether they are produced by an unusual type of supernova or by interstellar gas falling into a black hole.

Analysis of the brightest LFBOT to-date, named AT 2024wpp and discovered last year, shows that they’re neither. Instead, a team led by researchers from the University of California, Berkeley, concluded that they are caused by an extreme tidal disruption, where a black hole of up to 100 times the mass of our Sun completely shreds its massive star companion within days.

This discovery resolves a decade-long conundrum but also illustrates the many varieties of stellar calamities that astronomers encounter, each with its characteristic spectrum of light that evolves over time. Figuring out the processes that produce these unique light signatures tests current knowledge of the physics of black holes and helps astronomers understand the evolution of stars in our Universe.

The team’s analysis of AT 2024wpp is presented in two papers recently accepted by The Astrophysical Journal Letters. The studies utilize data from a large collection of telescopes that measured the various wavelengths of light emitted by the LFBOT [2]. Crucial near-infared data was collected with the Flamingos-2 instrument on the Gemini South telescope in Chile, one half of the International Gemini Observatory, funded in part by the U.S. National Science Foundation and operated by NSF NOIRLab.

“The ongoing discovery of luminous fast blue optical transients shows that Gemini South and other ground-based astronomical facilities are primed to characterize these mysterious objects,” says Martin Still, NSF program director for the International Gemini Observatory. “We expect the NSF–DOE Vera C. Rubin Observatory will spot large numbers of these transient objects, giving Gemini and other telescopes unprecedented opportunities for detailed follow-up observations.”

LFBOTs got their name because they are bright — they’re visible over distances of hundreds of millions to billions of light years — and last for only a few days. They produce high-energy light ranging from the blue end of the optical spectrum through ultraviolet and X-ray. The first was seen in 2014, but the first with sufficient data to analyze was recorded in 2018 and, per the standard naming convention, was called AT 2018cow. The name led researchers to refer to it as the Cow, and subsequent LFBOTs have been called, tongue in cheek, the Koala (ZTF18abvkwla), the Tasmanian devil (AT 2022tsd) and the Finch (AT 2023fhn). Perhaps AT 2024wpp will be known as the Wasp.

The realization that AT 2024wpp could not have resulted from a supernova came after the researchers calculated the energy it emitted. It turned out to be 100 times greater than what would be produced in a normal supernova. The radiated energy would require the conversion of about 10% of the rest-mass of the Sun into energy over a very short time scale of weeks.

Specifically, the Gemini South observations revealed an excess of near-infrared light being emitted from the source. This is only the second time astronomers have observed such a phenomenon (the other case being AT 2018cow), which is clearly not present in ordinary stellar explosions. These observations establish the near-infrared excess as a hallmark feature of FBOTs, though no model can explain this occurrence.

“The sheer amount of radiated energy from these bursts is so large that you can't power them with a core collapse stellar explosion — or any other type of normal stellar explosion,” says Natalie LeBaron, UC Berkeley graduate student and first author on the paper presenting the Gemini data [1]. “The main message from AT 2024wpp is that the model that we started off with is wrong. It’s definitely not just an exploding star.”

The researchers hypothesize that the intense, high-energy light emitted during this extreme tidal disruption was a consequence of the long parasitic history of the black hole binary system. As they reconstruct this history, the black hole had been sucking material from its companion for a long time, completely enshrouding itself in a halo of material too far from the black hole for it to swallow.

Then, when the companion star finally got too close and was torn apart, the new material became entrained into the rotating accretion disk and slammed against the existing material, generating X-ray, ultraviolet, and blue light. Much of the gas from the companion also ended up swirling toward the poles of the black hole, where it was ejected as a jet of material. The team calculated that the jets were traveling at about 40% of the speed of light and generated radio waves when they encountered surrounding gas.

Like most LFBOTs, AT 2024wpp is located in a galaxy with active star formation, so large stars like these are expected. AT 2024wpp is 1.1 billion light years away and between 5 and 10 times more luminous than AT 2018cow.

The estimated mass of the companion star that was shredded was more than 10 times the mass of the Sun. It may have been what’s known as a Wolf-Rayet star, which is a very hot and evolved star that has already used up much of its hydrogen. This would explain the weak hydrogen emission from AT 2024wpp.

Source: NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)/News

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Notes

[1] Natalie LeBaron et al. presents an analysis of the optical, ultraviolet and near infrared data. A companion paper by Nayana A.J. et al. presents an analysis of the X-ray and radio data.

[2] In addition to Gemini South, this study includes observations made with NASA’s Chandra X-ray Observatory, Swift-XRT, the Nuclear Spectroscopic Telescope Array (NuSTAR), the Atacama Large Millimeter/submillimeter Array (ALMA), the Australia Telescope Compact Array (ATCA), the Ultra-Violet/Optical Telescope (UVOT) on NASA’s Neil Gehrels Swift Observatory, the W.M. Keck Observatory, and Lick Observatory.

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More information

This research was presented in a paper titled “The Most Luminous Known Fast Blue Optical Transient AT 2024wpp: Unprecedented Evolution and Properties in the Ultraviolet to the Near-Infrared,” uploaded to arXiv and accepted for publication in The Astrophysical Journal Letters.

The team is composed of N. LeBaron (UC Berkeley, USA), R. Margutti (UC Berkeley, USA), R. Chornock (UC Berkeley, USA), N. A. J. (UC Berkeley, USA), O. Aspegren (UC Berkeley, USA), W. Lu (UC Berkeley, USA), B. D. Metzger (Columbia University/Flatiron Institute, USA), D. Kasen (UC Berkeley/Lawrence Berkeley National Laboratory, USA), T. G. Brink (UC Berkeley, USA), S. Campana (INAF, Italy), P. D’Avanzo (INAF, Italy), J. T. Faber (California Institute of Technology, USA), M. Ferro (University of Insubria/INAF, Italy), A. V. Filippenko (UC Berkeley, USA), R. J. Foley (UC Santa Cruz, USA), X. Guo (UC Berkeley, USA), E. Hammerstein (UC Berkeley, USA), S. W. Jha (Rutgers University, USA), C. D. Kilpatrick (Northwestern University, USA), G. Migliori (INAF, Italy), D. Milisavljevic (Purdue University, USA), K. C. Patra (UC Santa Cruz, USA), H. Sears (Rutgers University, USA), J. J. Swift (The Thacher School, USA) , S. Tinyanont (NARIT, Thailand), V. Ravi (California Institute of Technology, USA), Y. Yao (UC Berkeley, USA), K. D. Alexander (Steward Observatory, USA), P. Arunachalam (UC Santa Cruz, USA), E. Berger (Center for Astrophysics | Harvard & Smithsonian, USA), J. S. Bright (University of Oxford, UK), C. Cynamon (Supra Solem Observatory, USA), K. W. Davis (UC Santa Cruz, USA), B. Garretson (Purdue University, USA), P. Guhathakurta (UC Santa Cruz, USA), W. V. Jacobson-Galán (California Institute of Technology, USA), D. O. Jones (Gemini Observatory/NSF NOIRLab, USA), R. Kaur (UC Santa Cruz, USA), S. Kimura (Willamette University, USA), T. Laskar (University of Utah, USA/Radboud University, The Netherlands), Morgan Nuñez (San Francisco State University, USA), M. Schwab (Rutgers University, USA), M. D. Soraisam (Gemini Observatory/NSF NOIRLab, USA), N. Suzuki (Lawrence Berkeley National Laboratory/Florida State University, USA), K. Taggart (UC Santa Cruz, USA), E. Wiston (UC Berkeley, USA), Y. Yang (Tsinghua University, China), and W. Zheng (UC Berkeley, USA).

NSF NOIRLab, the U.S. National Science Foundation center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), NSF Kitt Peak National Observatory (KPNO), NSF Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and NSF–DOE Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona.

The scientific community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence of I’oligam Du’ag to the Tohono O’odham Nation, and Maunakea to the Kanaka Maoli (Native Hawaiians) community.

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Links

• Read the paper: The Most Luminous Known Fast Blue Optical Transient AT 2024wpp: Unprecedented Evolution and Properties in the Ultraviolet to the Near-Infrared


• UC Berkeley press release


• Read the companion paper: The Most Luminous Known Fast Blue Optical Transient AT 2024wpp: Unprecedented Evolution and Properties in the X-rays and Radio


• Chandra X-ray Observatory announcement


• Photos of the Gemini South telescope


• Videos of the Gemini South telescope


• Check out other NOIRLab Science Releases

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Contacts:

Natalie LeBaron
Graduate student
UC Berkeley
Email: nlebaron@berkeley.edu

Josie Fenske
Public Information Officer
NSF NOIRLab
Email: josie.fenske@noirlab.edu

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Astronomers Discover the First Gravitationally Lensed Superluminous Supernova

SN 2025wny

Gravitationally lensed superluminous supernova
An artist’s interpretation of light from a supernova passing through a gravitational lens, reaching Earth at different times.
Credit: Oskar Klein Center, University of Stockholm / Samuel Avraham & Joel Johansson.

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Maunakea, Hawaiʻi – An international team of astronomers using a combination of ground-based telescopes, including the W. M. Keck Observatory on Maunakea, Hawaiʻi Island, has discovered the first-ever spatially resolved, gravitationally lensed superluminous supernova. The object, dubbed SN 2025wny, offers a rare look at a stellar cataclysm from the early Universe and provides a striking confirmation of Einstein’s theory of general relativity.

SN 2025wny lies so far away that its light has traveled 10 billion years to reach Earth; the Universe was just 4 billion years old when the explosion occurred. Normally, a supernova at this distance would be far too faint to detect from the ground. But two foreground galaxies act as a natural gravitational “magnifying glass,” boosting the supernova’s brightness by a factor of 50 and splitting it into distinct, spatially separated images.

“This is nature’s own telescope,” says Joel Johansson, lead author from the Oskar Klein Centre, Stockholm University. “The magnification lets us study a supernova at a distance where detailed observations would otherwise be impossible.”

The study, led by Stockholm University, is published in The Astrophysical Journal Letters.

An artist’s interpretation of light from a supernova passing through a gravitational lens, reaching Earth at different times.
Credit: Oskar Klein Center, University of Stockholm / Samuel Avraham & Joel Johansson.

A new method to probe the expansion of the universe

Because each of the multiple lensed images takes a slightly different path around the intervening galaxies, their arrival times differ. Measuring these time delays provides a powerful, independent method to determine the Hubble constant—the rate at which the Universe is expanding.

A major unsolved problem in modern cosmology is the Hubble tension—the growing mismatch between measurements of the Universe’s expansion rate made from the early Universe versus those made from nearby objects. The disagreement suggests that our current cosmological model may be incomplete. Strongly lensed supernovae like SN 2025wny offer a new, independent way to measure this expansion rate through time-delay differences between the lensed images, helping determine whether the tension reflects new physics or limitations in existing methods.

“A lensed supernova with multiple, well-resolved images provides one of the cleanest ways to measure the expansion rate of the Universe,” says Ariel Goobar of the Oskar Klein Centre. “SN 2025wny is an important step toward resolving one of cosmology’s most significant challenges.”

A surprising and exceptionally hot explosion

Superluminous supernovae are extremely bright, rare explosions. SN 2025wny stands out even in this elite category: its early ultraviolet light, stretched into optical wavelengths by cosmic expansion, revealed an exceptionally hot, brilliant event.

The supernova’s intense brightness illuminated its host galaxy, allowing astronomers to identify narrow absorption lines from elements such as carbon, iron, and silicon. These fingerprints point to a low-metallicity, star-forming dwarf galaxy—exactly the kind of environment thought to produce superluminous supernovae during the Universe’s youth.

How the Discovery Was Made

The discovery relied on a chain of cutting-edge observatories working together on scientific breakthroughs. The Zwicky Transient Facility (ZTF) at Palomar Observatory in California first detected the explosion during its nightly monitoring of the sky. The Nordic Optical Telescope (NOT) on La Palma in the Canary Islands provided early spectroscopy of the transient, Liverpool Telescope (LT) also on La palma provided four separate images of SN 2025wny, and Keck Observatory ultiumately provided the decisive spectra that confirmed both the supernova type and its extreme distance.

Yu-Jing Qin, a postdoctoral researcher at Caltech, led a series of spectroscopic observations using Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS), targeting each of the individual supernova images and the lensing galaxies.

The Keck spectra revealed a forest of narrow absorption lines from the supernova’s host galaxy – the fingerprints of elements such as carbon, iron and silicon – which nailed down the redshift and nature of the event.

“The spectrum taken with LRIS provides the most convincing measurement of its distance/redshift and pinpointed its classification as a superluminous supernova, which is a rare subclass. We were really impressed by the data quality and are pursuing further observations using other Keck instruments,” said Qin.

These rapid-response observations were enabled by Keck Observatory’s Target of Opportunity (ToO) policy, which allows scientists to request immediate access for short-lived cosmic events.

“It’s always exciting to get a request for a very rapid response to a transient event like this,” said John O’Meara, Chief Scientist and Deputy Director for Keck Observatory. “Keck was ready to respond, and we were happy to deliver and participate in this breakthrough.”

What Comes Next?

SN 2025wny demonstrates that strongly lensed supernovae at very high redshifts can be discovered and resolved with today’s surveys—a crucial proof of concept ahead of the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), which is expected to uncover hundreds more.

Follow-up observations with the Hubble Space Telescope and James Webb Space Telescope are already underway. These data will refine the gravitational lens model, map the multiple images with exceptional precision, and ultimately measure the time delays needed for a new, independent determination of the Hubble constant.

The extraordinary magnification also offers an unprecedented view into how such extreme explosions work and how stars evolved in the early Universe.

Source: W.M. Keck Observatory/Science News

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About LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion.

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

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