A cosmic construction project

MACS J0553.4-3342

A galaxy cluster in deep space. It is filled with elliptical galaxies: small, bright white glowing ovals. The two largest elliptical galaxies, left and right of center, are bright cores that radiate light. Unrelated, distant galaxies are scattered around as red smudges and dots.Many of these are stretched out into red arcs and lines by the galaxy cluster’s strong gravity, creating multiple images in places. Numerous spiral galaxies and bright stars appear in the foreground. Credit: ESA/Webb, NASA & CSA, S. Fujimoto

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In today’s Picture of the Month from the NASA/ESA/CSA James Webb Space Telescope we are taken on a visit to a building site of significant scale. The project is a galaxy cluster named MACS J0553.4-3342, located in the constellation Columba (the Dove).

MACS J0553.4-3342 is situated at a redshift of 0.412. Redshift is a measure of how much the cluster’s light has been stretched by the expansion of the Universe over the course of its long journey to Webb’s mirrors; this unassuming number tells us that we are seeing MACS J0553.4-3342 as it was 4.4 billion years in the past. But for a galaxy cluster, this is relatively young. In fact, observations with the NASA/ESA Hubble Space Telescope and other telescopes show a cluster still in the process of being built.

MACS J0553.4-3342 is composed of two sub-clusters — roughly equal in mass — that are actively merging. The two subclusters have already slammed through each other and travelled over one million light-years apart, but they will eventually come back together again and again until they finally merge. The construction process is messy, and MACS J0553.4-3342 is filled with extremely hot gas that radiates powerful X-rays. Each subcluster is anchored on an immensely bright and massive elliptical galaxy, which are easily identifiable as the two brightest points in the centre of this scene with the largest glowing halos around them. The many smaller white elliptical galaxies are bound to one of the two subclusters by gravity, and will be incorporated into the final galaxy cluster. This image also features many foreground galaxies — spirals and dusty discs that are unrelated to MACS J0553.4-3342 — and prominent bright stars in our own Milky Way galaxy.

Even mid-way through its construction, the titanic clumps of matter swirling around in this galaxy cluster have built a device that is already very useful for us here on Earth: a gravitational lens. The extreme and concentrated mass in MACS J0553.4-3342 curves light with its gravity, similar to how a glass lens bends and focuses light. In this image you can see prominent orange, stretched-out arcs alongside each of the subclusters. These arcs are images of distant background galaxies, whose light has been warped by the galaxy cluster’s gravitational pull. The arc on the left side, three bright spots joined together, is actually three images of a single background galaxy! A forest of smaller arcs and lines are scattered across the image too; such a fantastic view appears in few other places in the Universe.

Look in the right spot, however, and this galaxy cluster turns from a distorting funhouse mirror into a precision scientific device. The gravitational lensing focuses light, magnifying objects and enhancing their brightness so if they lie in exactly the right place, background galaxies and even individual stars that would have been far too faint and distant to spot will be made visible. By carefully mapping out the mass of the cluster, researchers can reconstruct where and how strongly it distorts light from our point of view, then search for serendipitously-magnified distant objects to study. The arcs we can see in MACS J0553.4-3342 already show a few galaxies from less than a billion years after the Big Bang.

This image, taken with Webb’s Near-Infrared Camera (NIRCam), stems from a survey programme named VENUS (#6882). Astronomers aimed to create a collection of deep, high-quality images of massive galaxy clusters like MACS J0553.4-3342 across a wide range of infrared wavelengths, greatly expanding the area covered by Webb’s sensitive instruments. Researchers can then scour the clusters for distant and faint objects that have been brightened through gravitational lensing, from young galaxies and low-mass black holes to supernova explosions and individual stars. Gravitational lensing has been key to many of Webb’s most dramatic discoveries in recent years, and having many more examples of it allows us to systematically study the distant past and the evolutionary stages of the galaxies, stars and black holes we see today.

Source: ESA/Webb/potm

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Links

• Pan video: MACS J0553.4-3342
• Zoom video: MACS J0553.4-3342

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Dropping Dark Matter from the Pisa Tower: A New Test of the Equivalence Principle with the Distortion of Time in Galaxy Clusters

A sketch of the Pisa tower on top of the Perseus cluster of galaxies observed by the Euclid satellite. Background image: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi.

All types of ordinary matter fall in a gravitational potential in the same way, while dark matter may experience deviations. The depth of the gravitational potential can be measured through the impact of the time distortion on light, which changes frequency and hence colour in escaping the potential to reach an observer. © MPA

Predicted precision on deviations from the weak equivalence principle as a function of the total number of galaxies in galaxy clusters used to perform the test. The vertical line indicates the number used in the first detection of the distortion of time. The different colours correspond to more or less optimistic assumptions on the other free parameters involved in the test, ranging from assuming perfect knowledge of their values (black) to no knowledge (green).© MPA

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Does the mysterious dark matter experience gravity in the same way as ordinary matter? A team of scientists from MPA and the University of Geneva (Switzerland) has developed a new method to answer this question by measuring the time dilation in galaxy clusters. With future datasets, this method could detect violations of the equivalence principle at the level of a few percent.

In the 16th century, the Italian scientist Galileo Galilei is said to have dropped objects with different masses from the Leaning Tower of Pisa. With this experiment – possibly only imagined – he demonstrated that the acceleration of different bodies does not depend on their composition or mass. Since then, this seemingly counter-intuitive fact has become a fundamental pillar in our understanding of gravity, known as the weak equivalence principle. This principle states that any particle, regardless of its nature, experiences gravity in the same way.

Several experiments have confirmed with very high precision that the weak equivalence principle holds for all particles making up the ordinary matter around us. However, astrophysical and cosmological observations indicate that around 85 % of the matter in the Universe consists of unknown dark matter, which does not emit light and can only be probed through its gravitational impact on visible matter. If Galileo could have thrown a small amount of dark matter from the Pisa tower, would it have experienced the same acceleration as the other bodies? This remains a crucial open question, which could help shedding light on the nature of this mysterious component.

A team of researchers from MPA and the University of Geneva (Switzerland) – Sveva Castello, Enea Di Dio and Camille Bonvin – is determined to answer this question. Since dark matter has never been detected directly nor produced in a laboratory experiment, it is not possible to simply drop it from the Pisa tower. However, the team has designed a new method to perform an analogous experiment to Galileo’s in galaxy clusters. These are the largest gravitationally bound objects in the Universe and therefore provide the ideal environment to study the behaviour of dark matter under gravity. The new test consists in comparing the observed motion of the galaxies inside the clusters with the distortion of time generated by the clusters themselves.

Understanding the idea behind this test requires a small detour to the realm of Einstein’s theory of general relativity, providing our modern understanding of gravity. According to general relativity, the Universe can be described as a four-dimensional spacetime that gets distorted like a tablecloth in the presence of any object with a mass, such as galaxy clusters. This generates gravitational potential wells, which determine the motion of any particle under gravity. These distortions affect not only space but also time, so that a clock located at the bottom of a potential well ticks more slowly than one outside of it. This effect, known as time dilation or distortion of time, provides a direct measure of the depth of the gravitational potential well generated by a massive object.

If dark matter violates the weak equivalence principle, for example due to some unknown interactions, its motion under gravity will be different from the one predicted by general relativity. Since galaxies are mostly composed of dark matter, such a violation will impact their observed velocities inside a cluster. They will then move too fast or too slowly compared to the gravitational potential well of the cluster inferred from the distortion of time, clearly indicating an anomaly. Therefore, comparing galaxy velocities and the distortion of time in a galaxy cluster provides a powerful test of the weak equivalence principle.

Since we cannot send clocks across cosmological distances, how can we measure the distortion of time in galaxy clusters located billions of light-years away? This can be achieved by considering the impact of the distortion of time on light. Due to this effect, the wavelength of light emitted by galaxies in a cluster gets stretched and experiences a frequency shift, which is translated into a change of its observed colour. This leads to an observable gravitational redshift, which can be disentangled from other effects that change the colour of the light thanks to its symmetry properties when considering pairs of galaxies. This technique led to a first detection of this effect in 2011 by Radosław Wojtak, Steen H. Hansen and Jens Hjorth, who used a catalogue of around 100’000 galaxies in clusters by the Sloan Digital Sky Survey.

In this new study, the MPA-Geneva team predicted that existing measurements of the distortion of time can detect deviations from the weak equivalence principle at the level of 7-14 %. Ongoing galaxy surveys, such as the Euclid satellite and the Dark Energy Spectroscopic Instrument (DESI), will give access to larger samples of galaxy clusters and thus lead to an increased precision. In a realistic scenario, future datasets will be sensitive to violations of the equivalence principle at the level of a few percent.

As a next step, the team plans to apply the test to data. This will enable them to repeat Galileo’s experiment on astrophysical scales, providing crucial information on the properties of the mysterious dark matter in galaxy clusters. The discovery of a violation of the weak equivalence principle would have profound implications for cosmology, astrophysics and particle physics, and may also affect our fundamental understanding of gravity.

Source: Max Planck Institute for Astrophysics/Research Highlights

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Author:

Dr. Sveva Castello
Postdoc
Tel: 2007
Email: svevacas@mpa-garching.mpg.de

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NASA’s Webb Reveals Black Hole That Formed Before Its Galaxy

Little Red Dot Abell2744-QSO1 (NIRCam Image)

An image from NIRCam on NASA’s James Webb Space Telescope shows Little Red Dot Abell2744-QSO1, magnified and triply imaged by galaxy cluster Abell 2744 (Pandora’s Cluster). Credit Image: NASA, ESA, CSA, Lukas Furtak (Ben-Gurion University); Image Processing: Alyssa Pagan (STScI)

Little Red Dot Abell2744-QSO1a (NIRCam Image with NIRSpec IFU Velocity Map)

An image detail from NIRCam (left) on NASA’s James Webb Space Telescope shows Little Red Dot Abell2744-QSO1. A map of gas velocity in QSO1 (right), made using the IFU on NIRSpec, shows evidence for a 50-million-solar-mass black hole at the center. Credit Image: NASA, ESA, CSA, Ignas Juodžbalis (Cambridge), Cosimo Marconcini (University of Florence), Roberto Maiolino (Cambridge), Francesco D'Eugenio (Cambridge), Hannah Übler (MPE); Image Processing: Alyssa Pagan (STScI)

Little Red Dot Abell2744-QSO1 (NIRCam Compass Image)

Image of Abell 2744 and Little Red Dot Abell2744-QSO1, captured by Webb’s NIRCam, with compass arrows, scale bar, and color key for reference. Credit Image: NASA, ESA, CSA, Lukas Furtak (Ben-Gurion University); Image Processing: Alyssa Pagan (STScI)

Little Red Dot Abell2744-QSO1: Sonification of Gas Velocity Around a Supermassive Black Hole (NIRCam and NIRSpec IFU)

A sonification is a translation of data into sound. In this sonification, the velocity of hydrogen gas moving around a black hole in the center of a Little Red Dot known as Abell2744-QSO1 (QSO1) is translated into sounds of varying pitch (or frequency). The faster the gas is moving toward the telescope, the higher the pitch. The faster it is moving away from the telescope, the lower the pitch. Credit Sonification: NASA, ESA, CSA, STScI, Christopher Britt (STScI), Ralf Crawford (STScI), Alyssa Pagan (STScI), Margaret Carruthers (STScI); Science: Ignas Juodžbalis (Cambridge), Cosimo Marconcini (University of Florence), Roberto Maiolino (Cambridge), Francesco D'Eugenio (Cambridge), Hannah Übler (MPE)

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Which comes first, the galaxy or the black hole? We don’t know, but scientists have long thought it could be the galaxy: Large stars within an existing galaxy consume their fuel and collapse to form black holes, which can gobble up surrounding material and merge over time to form more massive entities.

But it’s hard to figure out how black holes millions to billions of times the mass of the Sun, thousands of which have now been detected in the early universe, could have grown so quickly from such small seeds.

Now, researchers using NASA’s James Webb Space Telescope have detected clear evidence that some supermassive black holes were enormous from the beginning, forming without a stellar collapse phase, and without a significantly more massive host galaxy to feed them.

“This is a remarkable finding,” said Roberto Maiolino of University of Cambridge in the United Kingdom, co-author of studies published in Nature and the Monthly Notices of the Royal Astronomical Society. “It’s a paradigm shift, a total revisiting of the classical scenarios of how black holes form and grow.”

Little Red Dot QSO1

The team’s conclusion is based on detailed observations of Abell2744-QSO1 (QSO1), a prototypical Little Red Dot that existed just 700 million years after the big bang.

Although QSO1 is only 1,300 light-years across, and its light has been traveling for more than 13 billion years, it is easier to study than most other Little Red Dots because it is gravitationally lensed by galaxy cluster Abell 2744 (Pandora’s Cluster). QSO1 is both magnified and triply imaged, appearing in three different locations in the sky.

Initial studies of QSO1 revealed compelling evidence that it may be little more than a cloud of glowing hydrogen and helium gas circling a supermassive black hole estimated at 40 million times the mass of the Sun. But as with other early black holes discovered by Webb, there was uncertainty about whether it really was that massive. “Before now, all of the mass measurements of black holes in the early universe have been indirect, based on assumptions from what we know about them in the local universe. We didn’t know if those assumptions really apply to the distant universe,” said co-author Francesco D’Eugenio, also of the University of Cambridge.

Mapping gas composition, velocity

The team recognized that if QSO1’s black hole is as massive as it looks, they should be able to use the integral field unit (IFU) on Webb’s NIRSpec (Near Infrared Spectrograph) to trace the effects of its gravity on the gas swirling around it, while also mapping the distribution of various elements in the gas.

Cambridge graduate student Ignas Juodžbalis and Cosimo Marconcini of the University of Florence, lead authors on one of the studies, used the IFU observations to map motions of hydrogen gas surrounding the black hole. When they plotted the rotation velocity as a function of distance from the center, they found that the gas has Keplerian motion: It orbits a central point in the same way that planets in our solar system orbit the Sun.

“This is important because it tells us that most of the mass of QSO1 is concentrated in the black hole at the center,” said Juodžbalis. “If the mass were more distributed, as it would be if there were a lot of stars, the gas would not have this perfect Keplerian rotation.”

Since Keplerian motion is governed by simple laws of gravity, the team was able to use the gas velocity measurements to calculate the black hole mass directly, a feat that had not previously been possible.

They found that not only is the black hole immense — roughly 50 million solar masses — it makes up, at minimum, an astonishing two-thirds of QSO1’s total mass. This proportion is thousands of times greater than in nearby galaxies, where supermassive black holes make up only a tiny fraction of the host galaxy’s total mass.

The IFU composition maps supported these results, showing that the gas throughout QSO1 is almost entirely hydrogen and helium, with very little of the heavier elements like oxygen that would be expected in a galaxy rich with stars and stellar debris. With a metallicity less than 0.5% of the Sun, QSO1 is one of the most pristine galactic environments ever measured.

“This is a phenomenal result,” said Maiolino. “It is the first direct measurement of a black hole mass within the first billion years after the big bang, and it is consistent with the previous measurements.” The team thinks this is a good sign that the assumptions used for indirect mass measurements are valid and the masses of other black holes in the early universe have not been overestimated.

Supermassive black hole origins

The team recognized that if QSO1’s black hole is as massive as it looks, they should be able to use the integral The outsized mass of QSO1 relative to its host galaxy suggests that it can’t have formed gradually from much smaller, stellar-mass black holes merging and feeding. “It seems that we have found a black hole that does not have a substantial host galaxy and that has predated stellar processes,” said Juodžbalis. “This is very exciting because it is evidence for primordial black holes or direct collapse black holes, which have been theorized but not confirmed.”

Whether QSO1’s black hole evolved from a “heavy seed” that formed within the first second of the big bang or somewhat later from the collapse of a giant cloud of gas, it was almost certainly born big, and may be in the early stages of building a galaxy around it.

The team thinks that Little Red Dots like QSO1 cannot have been rare in the early universe, and is in the process of analyzing similar objects to find out whether supermassive black holes actually do predate the galaxies where they currently reside.

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

Source: NASA's James Webb Space Telescope/Latest News

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Related Links

Watch: NASA Black Hole Visualization Takes Viewers Beyond the Brink

Explore more: ViewSpace | Black Holes: Searching for the unseen

Read more: Dissecting Supermassive Black Holes

Watch: What Webb Learns from Light

Explore more: NASA's Universe of Learning: Black Hole Resources

More Webb News

More Webb Images

Webb Science Themes

Webb Mission Page

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Galaxy Cluster Relaxed Now, but was Wild in the Past

Abell 2029
Credit: X-ray: NASA/CXC/CfA/C. Watson et al.; Optical: PanSTARRS;
Image Processing: NASA/CXC/SAO/N. Wolk and P. Edmonds

JPEG (172.4 kb) - Large JPEG (2 MB) - Tiff (54.5 MB) - More Images

A Tour of Abell 2029 - More Videos

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• New data from NASA’s Chandra X-ray Observatory suggests an event-filled past for the galaxy cluster Abell 2029.


• The X-rays reveal evidence for a collision with a smaller cluster about four billion years ago.


• A sloshing spiral structure was formed when the smaller cluster made its first pass through Abell 2029, pulling its gas sideways.


• Galaxy clusters are the largest structures in the Universe held together by gravity and are bellwethers for cosmic growth.

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The galaxy cluster Abell 2029 is sometimes described as “the most relaxed cluster in the Universe.” This moniker does not arise from some sort of mellow vibe, but rather because of how calm and undisturbed the superheated gas that pervades the cluster appears to be.

New observations from NASA’s Chandra X-ray Observatory clearly show that Abell 2029 had a much more colorful history than its current disposition suggests. The latest study finds that Abell 2029 is still settling down after a raucous collision with another smaller cluster about four billion years ago.

Galaxy clusters are the largest structures in the Universe held together by gravity. They are made up of hundreds or even thousands of galaxies, unseen dark matter, and a huge amount of gas that fills in the space between the galaxies. This gas is typically heated to millions of degrees, which makes it glow in X-ray light.

A team led by astronomers from Boston University (BU) and the Center for Astrophysics | Harvard & Smithsonian (CfA) obtained the deepest X-ray observation ever made of this cluster using Chandra. The results are described in an Astrophysical Journal paper led by Courtney Watson from BU and CfA.

The Chandra data reveal clear signs that this cluster did not have a mundane history. This new composite image shows evidence for the cluster’s previous shenanigans in the nautilus-like shape in the Chandra data (blue). Optical light from stars and galaxies in the same field of view appears mainly white in an image from Pan-STARRS, a telescope in Hawaii.

The team think the spiral shape in the hot gas formed when gas in the cluster sloshed to the side because of the gravitational effects of the cluster collision — similar to how wine moves in a wine glass. The sloshing spiral in Abell 2029 is one of the longest ever seen, extending about two million light-years from the center of the cluster.

Abell 2029, "splash" and "bay" features labeled. Credit: X-ray: NASA/CXC/CfA/C. Watson et al.; Optical: PanSTARRS; Image Processing: NASA/CXC/SAO/N. Wolk and P. Edmonds

Computer simulations of the collision suggest that the smaller cluster was about ten times less massive than the larger cluster. The sloshing spiral formed when the smaller cluster made its first pass through the larger cluster, pulling its gas sideways. The gravity of the larger cluster then caused the other cluster to slow down and get pulled back in for a second collision. This drove a shock front and left behind a wake of material, forming the splash region.

To uncover these various features the authors used a special technique that examined how much the cluster’s hot gas deviates from a symmetrical shape. Most of the hot gas is symmetrical and is approximately shaped like an oval. The authors removed (“subtracted”) this symmetrical oval shape from the original X-ray image. The remaining X-ray emission in the “subtracted image” clearly shows the unusual features of the sloshing spiral, the bay and the splash area. The shock front is too faint to be seen in this image.

The new composite image combines both the original X-ray and the subtracted X-ray images of the deep Chandra observations of Abell 2029. The subtracted X-ray image (light blue) strikingly shows the sloshing spiral. Most of the original X-ray image is a darker blue color, apart from the center of the image, which is light blue. Two other features — the bay and the splash area — are labeled in an annotated version. The brightness of the original image has been reduced in this image to better show the subtracted image.

Courtney Watson conducted this work as a graduate student at BU and a predoctoral fellow at CfA. In addition to Watson, the authors of the paper are Elizabeth Blanton (Boston University), who was the Principal Investigator for the Chandra observations, Scott Randall (CfA), Tracy Clarke (Naval Research Laboratory), and John ZuHone (CfA).

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.

There are several other key pieces of evidence for the past bash, never before seen together in a cluster, allowing the team to trace the collision history of the cluster in unprecedented detail. For example, the team sees hints of a wide “splash” of cooler gas created by the collision. There may also be a shock wave — akin to a sonic boom from a supersonic plane — in the superheated gas left over from the collision. Finally, there is a “bay” feature in the hot gas, which the researchers think might be caused by an overlap between the outer parts of the spiral and gas stripped away from the smaller cluster as it passed through the larger one. Though the authors think it is a relic from the collision, other explanations for this structure are also possible.

Quick Look: Galaxy Cluster Relaxed Now, but was Wild in the Past

Source: NASA’s Chandra X-ray Observatory

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Visual Description:

This release features a composite image of a galaxy cluster with a unique spiral shape, giving it the appearance of a giant galactic seashell floating in the star-speckled blackness of space.

In this composite image, the surrounding stars and individual galaxies appear white, captured in optical light from Pan-STARRS, a telescope in Hawaii. But much of the spiraling cluster is rendered in neon blues, representing X-ray gas observed by Chandra. This super-heated gas fills the space between galaxies, giving the cluster its spiral shape when observed by scientists using an X-ray telescope.

Here, the blue spiral begins as a pale blue dot at the center of the cluster. The spiral stream of light and dark neon blue gas then widens as it moves away from the center of the cluster, gently corkscrewing one full rotation as it extends two-million lightyears into the distance.

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Fast Facts for Abell 2029

Credit: X-ray: NASA/CXC/CfA/C. Watson et al.; Optical: PanSTARRS; Image Processing: NASA/CXC/SAO/N. Wolk and P. Edmonds

Release Date: May 12, 2026
Scale: Image is about 25 arcmin (7.2 million light-years) across.
Category: Groups & Clusters of Galaxies
Coordinates (J2000): RA 15h 10m 56.1s | Dec +05° 44´ 40.0"
Constellation: Virgo
Observation Dates: 24 observations from Apr 12, 2000 to Jun 6, 2023
Observation Time: 143 hours 3 minutes (5 days 23 hours 3 minutes)
Obs. ID: 891, 4977, 6101, 25496, 25814-25826, 26380, 26393, 26420, 26428, 27805, 27853, 27848
Instrument: ACIS
References: Watson, C.B., et al., 2026, ApJ, 996, 106.
Color Code: X-ray: blue and white; Optical: red, green, and blue
Distance Estimate: About 1.0 billion light-years from Earth (z~0.0767)

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How giant galaxies could form just 1.4 billion years after the Big Bang

Clusters of young galaxies in the early Universe that later grow into large clusters are called protoclusters. This artist’s impression of the protocluster SPT2349-56 shows interacting galaxies of different shapes and sizes, and gas (orange) that is torn apart and heated by tidal forces. Due to its great distance from Earth, we see SPT2349-56 as it looked only 1.4 billion years after the Big Bang, when the Universe was 10% of its current age. © N.Sulzenauer, MPIfR

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To the point

• An international team led by MPIfR researchers used data from the Atacama Large Millimeter/submillimeter Array (ALMA) to shed light on a central question of galaxy formation.


• They discovered shock-heated gas in one of the most spectacular aggregations of galaxies in the distant Universe.


• They found evidence that a giant elliptical galaxy may form through the rapid collapse of this infant galaxy cluster.

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New radio observations of molecular gas reveal how dozens of galaxies rapidly merge together in the early Universe.

Solving a Cosmic Mystery

A surprising observation has puzzled astronomers for two decades: Massive and evolved galaxies already existed just a few billion years after the Big Bang. Researchers expected to only find galaxies with young stars and ongoing star formation so early in the history of our Universe. Instead, there are many elliptical galaxies with older stellar populations and very little cold gas to form new stars. These observations pose a challenge to models of cosmological structure formation.

The group led by MPIfR astronomers now made a big leap in understanding these systems. “In a Universe where larger galaxies grow hierarchically through gravitational interactions and mergers of smaller building-blocks, some giant ellipticals must have formed completely differently than previously thought. Instead of slowly assembling mass throughout 14 billion years, a massive elliptical galaxy might swiftly emerge in just a few hundred million years. It can form through the collapse and coalescence of a major primordial structure, in the time it takes the Sun to orbit around the Milky Way’s center once”, explains Nikolaus Sulzenauer, PhD researcher at the MPIfR and University of Bonn, and first author leading the analysis. “We find that the structures with the very highest densities must have decoupled first from the Universe’s expansion at only 10% of the current cosmic age, and then rapidly assembled entire protoclusters.” The compression of gas sparks a cosmic firework, prodigiously bright as it is heated by star-birth activity. It is a beacon at far-infrared to millimeter wavelengths and thus accessible by observatories like ALMA and the Atacama Pathfinder Experiment (APEX).

Observing a Transformation

The team observed the cold gas and dust in the center of SPT2349-56, a protocluster seen just 1.4 billion years after the Big Bang and located in the southern constellation Phoenix. SPT2349-56 enables a rare glimpse of the first clusters, the main hubs of massive elliptical galaxies. “SPT2349-56 holds the record for the most vigorous stellar factory”, remarks Axel Weiß, who was also involved in the original discovery of SPT2349-56 with APEX. “In the center, we found four tightly-interacting galaxies forging one star every 40 minutes,” adds Ryley Hill from the University of British Columbia (UBC) in Canada. For comparison, it currently takes a whole year for three or four stars to form in the Milky Way.

“Importantly,” notes Sulzenauer “this galaxy quartet launches coherent giant tidal arms at 300 kilometers per second, stretching over an area much larger than the Milky Way. They glow intensely at submillimeter wavelength, their brightness boosted ten-fold by shock-waves exciting ionized carbon atoms. This bright emission allowed us to precisely measure the motion of gas in this gravitationally ejected spiral, resembling beads on a string encircling the protocluster core. To our surprise, clumps of tidal debris link to a chain of 20 additional colliding galaxies in the outer parts of the collapsing structure. This hints at a common origin. For the first time, we are witnessing the onset of a cascading merging transformation. Most of the 40 gas-rich galaxies in this core will be destroyed and will eventually transform into a giant elliptical galaxy within less than 300 million years – a mere blink of an eye.”

This radio image of the protocluster SPT2349-56 shows the intensity of ionized carbon (CⅡ) emitted at a wavelength of 158 micrometers. Star symbols mark the centers of galaxies, while orange contours highlight the tidal arms around the inner region. These tidally ejected, galaxy-scale gas clumps are found to be ten times brighter than expected. The size of the Milky Way disk is shown at the same scale. © N.Sulzenauer, MPIfR

Understanding How Galaxy Clusters Form

Duncan MacIntyre and Joel Tsuchitori, two UBC undergraduate students and part of the team, ran detailed numerical simulations. These were essential to bridge observations of this protocluster collapse with previous studies of mature galaxy clusters. The striking match between the different types of objects, found at different cosmic times, might not just demonstrate the importance of simultaneous major mergers during massive galaxy formation. It may also help to explain how heavy elements (such as carbon) are heated and transported throughout the first galaxy clusters.

“While our findings offer exciting new insights into rapid elliptical galaxy assembly, the various interactions between the merger shocks, gas heating from the growth of supermassive black holes, and their effect on the fuel for star-formation, remain big mysteries,” remarks Scott Chapman of Dalhousie University. “It might be too early to claim a full understanding of the ‘early childhood’ of giant ellipticals, but we have come a long way in linking tidal debris in protoclusters to the formation process of massive galaxies located in today’s galaxy clusters.”

Source: Max Planck Institute for Radio Astronomy/Press Release

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Additional Information

The following scientists affiliated to the MPIfR are coauthors of this publication:
Nikolaus Sulzenauer, Axel Weiß, Amélie Saintonge.

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Contacts:

Nikolaus Sulzenauer
Tel: +49 228 525-105
Email: nsulzenauer@mpifr-bonn.mpg.de
Max Planck Institute for Radio Astronomy, Bonn

Dr. Axel Weiß
Tel: +49 228 525-273
Email: aweiss@mpifr-bonn.mpg.de
Max Planck Institute for Radio Astronomy, Bonn

Dr. Nina Brinkmann
Press and Public Relations
Tel: +49 228 525-399
Email: brinkmann@mpifr-bonn.mpg.de
Max Planck Institute for Radio Astronomy, Bonn

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Original publication

Sulzenauer et al.
Bright [CⅡ]158µm Streamers as a Beacon for Giant Galaxy Formation in SPT2349−56 at z = 4.3>
The Astrophyiscal Journal 998 (2026)

DOI

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Video

How are giant elliptical galaxies formed in the early Universe?
Credit: N.Sulzenauer, MPIfR

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Graphics

spt2349_intensity_de 336.87 kB

spt2349_intensity_eng 332.3 kB

spt2349_tidal_streamers_full_nsulzenauer_2026 326.5 kB

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Links

Early Universe
Research area at the MPIfR

Paper on the discovery of the protocluster
Nature 556 (2018)

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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

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ALMA and the NSF VLA Use a Cosmic Lens to Reveal a Hyperactive Cradle of a Future Galaxy Cluster

PASASAGES Lensed Protocluster Core Candidate PJ0846+15

The galaxy cluster lens J0846 in optical light (bottom right), the ALMA view of dust-enshrouded, star-forming galaxies strongly lensed into bright arcs (top right), and a composite view (left) revealing at least 11 dusty galaxies in a compact protocluster core more than 11 billion light-years away, magnified by the foreground cluster’s gravity. Credit: NSF/AUI/NSF NRAO/B. Saxton; NSF/NOIRLab

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ALMA observations, together with NSF VLA, uncover the first strongly lensed protocluster core, revealing an intense burst of galaxy growth in the early universe

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA), together with the U.S. National Science Foundation Very Large Array (NSF VLA), have uncovered a rare, extraordinarily active region of the early universe where a future galaxy cluster is rapidly forming. By exploiting a powerful natural phenomenon known as gravitational lensing, ALMA revealed a compact, dust-enshrouded swarm of young galaxies forming stars at an exceptional rate more than 11 billion years ago.

The discovery marks the first strongly lensed protocluster core ever identified, providing an unprecedented, magnified view of one of the universe’s earliest large-scale structures in formation. Complementary observations with the NSF VLA helped characterize both the distant galaxies and the massive foreground cluster responsible for the lensing effect.

Galaxy clusters are the largest gravitationally bound structures in the universe. Their ancestors, known as protoclusters, are regions where galaxies are still assembling, rapidly converting gas into stars and growing in mass. Studying these systems allows astronomers to trace how today’s massive clusters emerged from much smaller, denser environments in the early cosmos.

ALMA’s high-resolution observations revealed that what initially appeared as a single bright source in all-sky survey data is actually a tightly packed group of at least 11 dusty, star-forming galaxies. These galaxies are confined to a region only a few hundred thousand light-years across — remarkably compact on cosmic scales — and are experiencing intense bursts of star formation.

Because these galaxies are heavily shrouded in dust, most of their visible light is absorbed and re-emitted at millimeter and submillimeter wavelengths. ALMA’s sensitivity to this cold dust and molecular gas allowed astronomers to detect the raw material fueling star formation and to measure the dynamics of the system with exceptional clarity.

The protocluster lies behind a massive foreground galaxy cluster whose gravity acts as a cosmic magnifying glass, bending and amplifying the light from the more distant system. This gravitational lensing effect dramatically boosts ALMA and the NSF VLA’s ability to resolve individual galaxies and study their properties in detail, effectively turning the universe itself into a telescope.

ALMA detected carbon monoxide (CO) emission, a key tracer of molecular gas, helping confirm that the galaxies share a common distance and form a physically connected structure. These observations show that the protocluster core contains enormous gas reservoirs capable of sustaining vigorous star formation and driving the rapid buildup of stellar mass.

Complementary observations with the NSF VLA provided radio-frequency data that helped map the foreground cluster and identify radio emission associated with both star formation and energetic processes within the system, strengthening the interpretation of the lensing configuration and the nature of the galaxies involved.

“Galaxy clusters are akin to a sprawling modern metropolis that was built upon an ancient civilization from the past. For example, if an archaeologist digs deeper into the ground, then they uncover an earlier civilization. Similarly, when astronomers observe objects farther away, they can look further back in time. In this way, the study of this distant protocluster gives us a glimpse into how one of the earliest ‘settlements’ of galaxies grew and evolved into the mature structures such as that foreground galaxy cluster that we observe today,” said Nicholas Foo, a graduate student at Arizona State University.

Protoclusters like this one represent the earliest construction phases of galaxy clusters seen in the present-day universe. By combining ALMA’s detailed view of cold gas and dust with complementary radio observations from the NSF VLA, astronomers can investigate how galaxies grow, interact, and evolve in the densest environments of the early cosmos.

This rare alignment of a young protocluster and a massive foreground lens provides an exceptional opportunity to test theories of galaxy and cluster formation. Future ALMA observations will further explore how these compact, dust-rich systems evolve and how their extreme environments shape the galaxies that will eventually populate massive clusters billions of years later.

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

Scientific Paper

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Additional Information

The results of this research appear as "PASSAGES: The Discovery of a Strongly Lensed Protocluster Core Candidate at Cosmic Noon" in the Astrophysical Journal by N. foo et al.

The original press release was published by the National Radio Astronomy Observatory of the United States, 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. The 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
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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New Discovery Challenges Evolution of Galaxy Clusters

Artist’s impression of the forming cluster SPT2349-56: radio jets from active galaxies embedded in a hot intracluster atmosphere (red), illustrating a large thermal reservoir of gas in the nascent cluster. Credit: Lingxiao Yuan. Hi-Res File

Hubble (blue) and James Webb (green and red) image shows dozens of active galaxies packed into the baby cluster SPT2349-56, seen when the Universe was only 1.4 billion years cold. The overlaid contours trace ALMA’s detection of the thermal Sunyaev-Zel’dovich effect, revealing the hot intracluster gas that fills the core of the infant cluster. Credit: Dazhi Zhou (UBC); HST, JWST (NASA/ESA/CSA) and ALMA (ESO/NAOJ/NRAO). Hi-Res File

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ALMA detects earliest hot intracluster atmosphere ever seen, revealing a huge thermal reservoir, and forcing astronomers to reconsider how galaxy clusters grew in the early Universe

Peering back in time, around 12 billion years, astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found the most distant and direct evidence of scorching gas in a forming galaxy cluster, SPT2349-56. The hot plasma, seen when the Universe was just 1.4 billion years old, is far hotter and more pressurized than current theories predicted for such an early system.

The team used an unusual observation technique called the thermal Sunyaev–Zel’dovich (tSZ) effect. Rather than looking for light from the gas itself, the tSZ effect reveals a small shadow cast by hot electrons found in galaxy clusters against the faint afterglow from the Big Bang in the cosmic microwave background.

“We didn’t expect to see such a hot cluster atmosphere so early in cosmic history,” said lead author Dazhi Zhou, a PhD candidate at the University of British Columbia, “In fact, at first I was skeptical about the signal because it was too strong to be real. After months of checks and tests, we confirmed that the intracluster gas in this young cluster is hotter and more energetic than many present-day clusters.”

Before this new result, astronomers assumed that at early cosmic epochs, galaxy clusters were still too immature to have fully developed and heated their intracluster gas. No hot cluster atmospheres had been directly detected in the first 3 billion years of cosmic history.

“SPT2349-56 changes everything we thought we understood,” said co-author Scott Chapman, a professor at Dalhousie University and affiliate professor at the University of British Columbia, who conducted the research while at the National Research Council of Canada (NRC), “Our measurements show a superheated cluster atmosphere only 1.4 billion years after the Big Bang, at a time when we thought the intracluster gas should still be relatively cool and slowly settling in. It suggests that the birth of massive clusters could be much more violent and efficient at heating the gas than our models assumed.”

SPT2349-56 is already famous as one of the most extreme infant clusters known. Its compact core, about the size of the halo surrounding the Milky Way, hosts several actively growing supermassive black holes and more than 30 starburst galaxies that together build stars thousands of times faster than our Galaxy. According to this study, powerful outbursts from these black holes, seen as bright radio galaxies, could be a natural way to inject the enormous amount of energy needed to overheat the intracluster gas so early.

​This new discovery suggests that in the Universe’s first billion years, energetic processes, like bursts from supermassive black holes and intense starbursts, could dramatically heat the surrounding gas in growing clusters. This overheating stage could be crucial for transforming these young cool galaxy clusters into the sprawling hot clusters seen today. It also suggests current models need to update ideas on how galaxies and their environments grow up.

This is the earliest direct detection of hot cluster gas ever reported, pushing the limits of how far back astronomers can study these environments. The discovery that massive reservoirs of hot plasma exist so early forces scientists to rethink the sequence and speed of galaxy cluster evolution. It also opens new questions about how supermassive black holes and galaxy formation shape the cosmos. “SPT2349-56 is a very strange and exciting laboratory. We see intense star formation, energetic supermassive black holes and this overheated atmosphere all packed into a young, compact cluster, ” added Zhou, “There is still a huge observational gap between this violent early stage and the calmer clusters we see later on. Mapping how their atmospheres evolve over cosmic time will be a very exciting direction for future work. ”

Source: National Radio Astronomy Observatory (NRAO)/News

Link: Scientific Paper

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About ALMA

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

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

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NASA's Chandra Rings in New Year With Champagne Cluster

Champagne Cluster
JPEG (326 kb) - Large JPEG (4.9 MB) - Tiff (94.5 MB) - More Images

A Tour of MSH 15-52 - More Videos

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Celebrate the New Year with the “Champagne Cluster,” a galaxy cluster seen in this new image from NASA’s Chandra X-ray Observatory and optical telescopes.

Astronomers discovered this galaxy cluster Dec. 31, 2020. The date, combined with the bubble-like appearance of the galaxies and the superheated gas seen with Chandra observations (represented in purple), inspired the scientists to nickname the galaxy cluster the Champagne Cluster, a much easier-to-remember name than its official designation of RM J130558.9+263048.4.

The new composite image shows that the Champagne Cluster is actually two galaxy clusters in the process of merging to form an even larger cluster. Multimillion-degree gas in galaxy clusters usually takes on an approximately circular or moderately oval shape in images, but in the Champagne Cluster it is more widely spread from top to bottom, revealing the presence of the two colliding clusters. Two clumps of individual galaxies making up the colliding clusters can be seen toward the top and bottom of center. (The image has been rotated clockwise by 90 degrees so that North points to the right.) The hot gas outweighs the combined mass in all of the hundred-plus individual galaxies in the newly forming cluster. The clusters also contain even larger amounts of unseen dark matter, the mysterious substance that pervades the universe.

In addition to the Chandra data, this new image contains optical data from the Legacy Surveys (red, green, and blue), which consists of three individual and complementary surveys from various telescopes in Arizona and Chile.

The Champagne Cluster is a member of a rare class of merging clusters, which includes the well-known Bullet Cluster, where the hot gas in each cluster has collided and slowed down, and there is a clear separation between the hot gas and the most massive galaxy in each cluster.

By comparing the data with computer simulations, astronomers came up with two possibilities for the history of the Champagne Cluster. One is that the two clusters already collided with each other over two billion years ago. After the collision the two clusters traveled outward and then were pulled back toward each other by gravity, and are now heading into a second collision. The other idea is that a single collision occurred about 400 million years ago, and the two clusters are now traveling away from each other after that collision. Researchers think further studies of the Champagne Cluster can potentially teach them how dark matter reacts to a high-speed collision.

A paper describing these results recently appeared in The Astrophysical Journal and is available online. The authors of the paper are Faik Bouhrik, Rodrigo Stancioli, and David Wittman, all from the University of California, Davis.

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's Chandra Rings in New Year With Champagne Cluster

Source: NASA’s Chandra X-ray Observatory

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Visual Description:

This release features a composite image of a galaxy cluster discovered on New Year's Eve day, 2020.

The cluster appears here as a large collection of brilliant white lights, each a distinct galaxy. A neon purple cloud stretches across the cluster's crowded core. Many of the hundred-plus galaxies in the cluster are in two clumps of galaxies towards the top and bottom of center. Some are encircled by a faint glowing haze, while a few foreground stars gleam with diffraction spikes. Some of the smaller galaxies are tinted blue, orange, or red, and some appear more oblong than round, suggesting spiral shapes viewed edge-on.

The neon purple cloud sits at the heart of the image, surrounding the most densely-packed part of the cluster. This cloud, which spreads vertically across the cluster, is multimillion-degree gas observed by Chandra. The two clumps of observable galaxies, and the spread of superheated gas, reveal that the Champagne Cluster is in fact two clusters in the process of colliding.

With the two clusters of sparkling light clinking together, and the auspicious discovery date, astronomers have dubbed the merged cosmic structure "The Champagne Cluster".

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Fast Facts for Champagne Cluster

Credit: X-ray: NASA/CXC/UCDavis/F. Bouhrik et al.; Optical:Legacy Survey/DECaLS/BASS/MzLS; Image Processing: NASA/CXC/SAO/P. Edmonds and L. Frattare
Release Date: December 30, 2025
Scale: Image is about 4.2 arcmin (3.8 million light-years) across.
Category: Groups & Clusters of Galaxies
Coordinates (J2000): RA 13h 05m 58s | Dec +26° 30´ 48.4"
Constellation: Coma Berenices
Observation Dates: Nov 18, 2012
Observation Time: 8 hours 12 minutes
Obs. ID: 14015
Instrument: ACIS
References: Bouhrik, F., Stancioli, R, Wittman, D, 2025, ApJ, 988, 166
Color Code: X-ray: purple; Optical: red, green, and blue
Distance Estimat: About 3.5 billion light-years from Earth (z=0.3069)

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Massive non-cool-core galaxy cluster explored with Chandra

Exposure-corrected 0.5–7 keV Chandra ACIS-I0–3 image of SPT-CL J0217-5014. The source extraction region, centered on the X-ray centroid, is shown by a white circle. The regions used for local background extraction are also indicated. All point sources were excluded from both the source and background regions during imaging and spectral analysis. Credit: arXiv (2025). DOI: 10.48550/arxiv.2512.04689

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Astronomers have employed NASA's Chandra spacecraft to perform X-ray observations of a massive galaxy cluster known as SPT-CL J0217-5014. Results of the observational campaign, published December 4 on the arXiv preprint server, yield important insights into the properties and nature of this cluster.

Enormous gravitationally-bound structures

Galaxy clusters contain up to thousands of galaxies bound together by gravity. They form through accretion of mass and infall of smaller sub-structures and are the largest known gravitationally-bound structures in the universe. Astronomers perceive galaxy clusters as excellent laboratories for studying galaxy evolution and cosmology.

SPT-CL J0217-5014 is a galaxy cluster at a redshift of 0.53, with a stellar mass of about 300 trillion solar masses, and super-solar iron abundance. Given that very little is known regarding the properties of this cluster, a team of astronomers led by Dan Hu of Masaryk University in Brno, Czech Republic, decided to investigate it with Chandra's Advanced CCD Imaging Spectrometer (ACIS)-I array.

"This study aims to evaluate its chemical and thermodynamic properties with a dedicated Chandra observation," the researchers write.

Disturbed non-cool-core cluster

Chandra imaging revealed that SPT-CL J0217-5014 has a disturbed morphology, characterized by a surface brightness edge at about 330,000 light years to the west and a tail-like feature extending to the east. Such morphology suggests a disturbed, non-relaxed intracluster medium (ICM).

Furthermore, the collected data indicate that SPT-CL J0217-5014 is a non-cool-core cluster. It turned out that the cluster has a sub-solar abundance, which is consistent with the typical metallicities observed in non-cool-core clusters. The astronomers explained that in such clusters, the dynamical processes could disrupt the cool core and tend to mix the central metal-rich gas with the outer ICM.

The study found that the power ratio and morphology index of SPT-CL J0217-5014 clearly place it in the dynamically disturbed regime. This suggests that the cluster may have experienced a merger event.

Potential companions of SPT-CL J0217-5014

The observation also resulted in the identification of three potential galaxy clusters near SPT-CL J0217-5014, which received the designations CIG 2, CIG 3, and CIG 4. They have lower mass and are less enriched than SPT-CL J0217-5014. This finding indicates that SPT-CL J0217-5014 is the primary, most massive cluster in this complex and likely sits at a node of the surrounding large-scale structure. "SPT-CL J0217–5014 likely underwent a relatively energetic, nearly head-on merger that disrupted a pre-existing cool core; ClG 2 and ClG 3 may be lower-mass companions that have merged with or fallen onto the main cluster, while ClG 4 aligns with the extension of the filamentary galaxy distribution, suggesting its association with a broader cosmic web," the authors conclude.

Source: Phys.org/Space News

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Written for you by our author: Tomasz Nowakowski, edited by Stephanie Baum, 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.

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More information: Dan Hu et al, A Chandra view of SPT-CL J0217-5014: a massive galaxy cluster at a cosmic intersection at z=0.53, arXiv (2025). DOI: 10.48550/arxiv.2512.04689

Journal information: arXiv

© 2025 Science X Network

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Explore further

X-ray observations reveal dynamic features of galaxy cluster PLCKG287

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Webb witnesses a feasting supermassive black hole in the early Universe

PR Image weic2522a
CANUCS-LRD-z8.6 in MACS J1149.5+2223

PR Image weic2522b
MACS J1149.5+2223

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Videos

 

PR Video weic2522a
Pan video: Galaxy cluster MACS J1149.5+2223

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Researchers using the NASA/ESA/CSA James Webb Space Telescope have confirmed an actively growing supermassive black hole within a galaxy just 570 million years after the Big Bang. Part of a class of small, very distant galaxies that have mystified astronomers, CANUCS-LRD-z8.6 represents a vital piece of this puzzle that challenges existing theories about the formation of galaxies and black holes in the early Universe. The discovery connects early black holes with the luminous quasars we observe today.

Over its first three years, Webb's surveys of the early Universe have turned up an increasing number of small, extremely distant, and strikingly red objects. These so-called Little Red Dots (LRDs) remain a tantalising mystery to astronomers, despite their unexpected abundance. The discovery in CANUCS-LRD-z8.6, made possible by Webb’s exceptional capabilities, has assisted in this hunt for answers. Webb’s Near-Infrared Spectrograph (NIRSpec) enabled researchers to observe the faint light from this distant galaxy and detect key spectral features that point to the presence of an accreting black hole.

Roberta Tripodi, lead author of the study and a researcher of the University of Ljubljana FMF, in Slovenia and INAF - Osservatorio Astronomico di Roma, in Italy, explained: "This discovery is truly remarkable. We’ve observed a galaxy from less than 600 million years after the Big Bang, and not only is it hosting a supermassive black hole, but the black hole is growing rapidly - far faster than we would expect in such a galaxy at this early time. This challenges our understanding of black hole and galaxy formation in the early Universe and opens up new avenues of research into how these objects came to be."

The team analysed the galaxy's spectrum, which showed gas which had been highly ionised by energetic radiation, and suggested it was rotating quickly around a central source. These features are key characteristics of an accreting supermassive black hole. The precise spectral data yielded an estimate of the black hole’s mass, revealing it to be unusually large for such an early stage in the Universe, and showed that CANUCS-LRD-z8.6 is compact and has not yet produced many heavy elements — a galaxy at an early stage of its evolution. This combination makes it an intriguing subject for study.

Additionally, the Webb spectroscopy allowed the team to measure how much energy is emitted at different wavelengths, from which they were able to characterise the galaxy’s physical properties. This allowed them to determine the mass of the galaxy’s stars and compare it with the black hole’s mass. "The data we received from Webb was absolutely crucial,” added Dr. Nicholas Martis, a collaborator from the University of Ljubljana, FMF, who helped analyse the spectrum of the source. “The spectral features revealed by Webb provided clear signs of an accreting black hole at the centre of the galaxy, something that could not have been observed with previous technology. What makes this even more compelling is that the galaxy’s black hole is overmassive compared to its stellar mass. This suggests that black holes in the early Universe may have grown much faster than the galaxies that host them."

Astronomers have previously observed that the mass of a supermassive black hole and its host galaxy are linked: the larger a galaxy grows, the larger its central black hole also becomes. CANUCS-LRD-z8.6 is the most massive host galaxy known at such an early time, yet its central black hole is even more massive than we would expect, defying the usual relation. The result suggests that black holes may have formed and started growing at an accelerated pace in the early Universe, even in relatively small galaxies.

"This discovery is an exciting step in understanding the formation of the first supermassive black holes in the Universe,” explained Prof. Maruša Bradač, leader of the group at the University of Ljubljana, FMF. “The unexpected rapid growth of the black hole in this galaxy raises questions about the processes that allowed such massive objects to emerge so early. As we continue to analyse the data, we hope to find more galaxies like CANUCS-LRD-z8.6, which could provide us with even greater insights into the origins of black holes and galaxies."

The team is already planning additional observations with the Atacama Large Millimetre/submillimetre Array (ALMA) and Webb to further study the cold gas and dust in the galaxy and to refine their understanding of the black hole’s properties. The ongoing research into this LRD is poised to answer crucial questions about the early Universe, including how black holes and galaxies co-evolved in the first billion years of cosmic history.

As astronomers continue to explore the early Universe with JWST, further surprises are expected to emerge, offering an increasingly detailed picture of how the first supermassive black holes grew and evolved, setting the stage for the formation of the luminous quasars that light up the Universe today.

The results were obtained by the CANUCS collaboration from the Webb observing programme #1208 (PI: C. J. Willott) and have been published today in Nature Communications.

Source: ESA/Webb/News/Press Releases

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More information

Webb is the largest, most powerful telescope ever launched into space. Under an international collaboration agreement, ESA provided the telescope’s launch service, using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace. ESA also provided the workhorse spectrograph NIRSpec and 50% of the mid-infrared instrument MIRI, which was designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.

Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).

Image Credit: ESA/Webb, NASA & CSA, G. Rihtaršič (University of Ljubljana, FMF), R. Tripodi (University of Ljubljana, FMF)

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Links

• Science paper
• Release on ESA website

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Contacts:

Roberta Tripodi
University of Ljubljana FMF, Slovenia
Email: roberta.tripodi@inaf.it

Bethany Downer
ESA/Webb Chief Science Communications Officer
Email: Bethany.Downer@esawebb.org

ESA Newsroom and Media Relations Office
Email: media@esa.int

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