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This graphic features data from NASA’s Chandra X-ray Observatory of the Cassiopeia A (Cas A) supernova remnant that reveals that the star’s interior violently rearranged itself mere hours before it exploded. The main panel of this graphic is Chandra data that shows the location of different elements in the remains of the explosion: silicon (represented in red), sulfur (yellow), calcium (green) and iron (purple). The blue color reveals the highest-energy X-ray emission detected by Chandra in Cas A and an expanding blast wave. The inset reveals regions with wide ranges of relative abundances of silicon and neon. This data, plus computer modeling, reveal new insight into how massive stars like Cas A end their lives.X-ray: NASA/CXC/Meiji Univ./T. Sato et al.; Image Processing: NASA/CXC/SAO/N. Wolk The inside of a star turned on itself before it spectacularly exploded, according to a new study from NASA’s Chandra X-ray Observatory. Today, this shattered star, known as the Cassiopeia A supernova remnant, is one of the best-known, well-studied objects in the sky.
Over three hundred years ago, however, it was a giant star on the brink of self-destruction. The new Chandra study reveals that just hours before it exploded, the star’s interior violently rearranged itself. This last-minute shuffling of its stellar belly has profound implications for understanding how massive stars explode and how their remains behave afterwards.
Cassiopeia A (Cas A for short) was one of the first objects the telescope looked at after its launch in 1999, and astronomers have repeatedly returned to observe it.
“It seems like each time we closely look at Chandra data of Cas A, we learn something new and exciting,” said Toshiki Sato of Meiji University in Japan who led the study. “Now we’ve taken that invaluable X-ray data, combined it with powerful computer models, and found something extraordinary.”
As massive stars age, increasingly heavy elements form in their interiors by nuclear reactions, creating onion-like layers of different elements. Their outer layer is mostly made of hydrogen, followed by layers of helium, carbon and progressively heavier elements – extending all the way down to the center of the star.
Once iron starts forming in the core of the star, the game changes. As soon as the iron core grows beyond a certain mass (about 1.4 times the mass of the Sun), it can no longer support its own weight and collapses. The outer part of the star falls onto the collapsing core, and rebounds as a core-collapse supernova.
The new research with Chandra data reveals a change that happened deep within the star at the very last moments of its life. After more than a million years, Cas A underwent major changes in its final hours before exploding.
“Our research shows that just before the star in Cas A collapsed, part of an inner layer with large amounts of silicon traveled outwards and broke into a neighboring layer with lots of neon,” said co-author Kai Matsunaga of Kyoto University in Japan. “This is a violent event where the barrier between these two layers disappears.”
This upheaval not only caused material rich in silicon to travel outwards; it also forced material rich in neon to travel inwards. The team found clear traces of these outward silicon flows and inward neon flows in the remains of Cas A’s supernova remnant. Small regions rich in silicon but poor in neon are located near regions rich in neon and poor in silicon.
The survival of these regions not only provides critical evidence for the star’s upheaval, but also shows that complete mixing of the silicon and neon with other elements did not occur immediately before or after the explosion. This lack of mixing is predicted by detailed computer models of massive stars near the ends of their lives.
There are several significant implications for this inner turmoil inside of the doomed star. First, it may directly explain the lopsided rather than symmetrical shape of the Cas A remnant in three dimensions. Second, a lopsided explosion and debris field may have given a powerful kick to the remaining core of the star, now a neutron star, explaining the high observed speed of this object.
Finally, the strong turbulent flows created by the star’s internal changes may have promoted the development of the supernova blast wave, facilitating the star’s explosion.
“Perhaps the most important effect of this change in the star’s structure is that it may have helped trigger the explosion itself,” said co-author Hiroyuki Uchida, also of Kyoto University. “Such final internal activity of a star may change its fate—whether it will shine as a supernova or not.”
These results have been published in the latest issue of The Astrophysical Journal and are available online.
To learn more about Chandra, visit:
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Read more from NASA’s Chandra X-ray Observatory Learn more about the Chandra X-ray Observatory and its mission here:
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Visual Description
This release features a composite image of Cassiopeia A, a donut-shaped supernova remnant located about 11,000 light-years from Earth. Included in the image is an inset closeup, which highlights a region with relative abundances of silicon and neon.
Over three hundred years ago, Cassiopeia A, or Cas A, was a star on the brink of self-destruction. In composition it resembled an onion with layers rich in different elements such as hydrogen, helium, carbon, silicon, sulfur, calcium, and neon, wrapped around an iron core. When that iron core grew beyond a certain mass, the star could no longer support its own weight. The outer layers fell into the collapsing core, then rebounded as a supernova. This explosion created the donut-like shape shown in the composite image. The shape is somewhat irregular, with the thinner quadrant of the donut to the upper left of the off-center hole.
In the body of the donut, the remains of the star’s elements create a mottled cloud of colors, marbled with red and blue veins. Here, sulfur is represented by yellow, calcium by green, and iron by purple. The red veins are silicon, and the blue veins, which also line the outer edge of the donut-shape, are the highest energy X-rays detected by Chandra and show the explosion’s blast wave.
The inset uses a different color code and highlights a colorful, mottled region at the thinner, upper left quadrant of Cas A. Here, rich pockets of silicon and neon are identified in the red and blue veins, respectively. New evidence from Chandra indicates that in the hours before the star’s collapse, part of a silicon-rich layer traveled outwards, and broke into a neighboring neon-rich layer. This violent breakdown of layers created strong turbulent flows and may have promoted the development of the supernova’s blast wave, facilitating the star’s explosion. Additionally, upheaval in the interior of the star may have produced a lopsided explosion, resulting in the irregular shape, with an off-center hole (and a thinner bite of donut!) at our upper left.
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Last Updated Aug 28, 2025 EditorLee MohonContactCorinne M. Beckingercorinne.m.beckinger@nasa.govLocationMarshall Space Flight Center Related Terms
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By NASA
Explore Webb Webb News Latest News Latest Images Webb’s Blog Awards X (offsite – login reqd) Instagram (offsite – login reqd) Facebook (offsite- login reqd) Youtube (offsite) Overview About Who is James Webb? Fact Sheet Impacts+Benefits FAQ Science Overview and Goals Early Universe Galaxies Over Time Star Lifecycle Other Worlds Observatory Overview Launch Deployment Orbit Mirrors Sunshield Instrument: NIRCam Instrument: MIRI Instrument: NIRSpec Instrument: FGS/NIRISS Optical Telescope Element Backplane Spacecraft Bus Instrument Module Multimedia About Webb Images Images Videos What is Webb Observing? 3d Webb in 3d Solar System Podcasts Webb Image Sonifications Webb’s First Images Team International Team People Of Webb More For the Media For Scientists For Educators For Fun/Learning 6 Min Read Webb Narrows Atmospheric Possibilities for Earth-sized Exoplanet TRAPPIST-1 d
This artist’s concept depicts planet TRAPPIST-1 d passing in front of its turbulent star, with other members of the closely packed system shown in the background. Full illustration and caption show below. Credits:
NASA, ESA, CSA, Joseph Olmsted (STScI) The exoplanet TRAPPIST-1 d intrigues astronomers looking for possibly habitable worlds beyond our solar system because it is similar in size to Earth, rocky, and resides in an area around its star where liquid water on its surface is theoretically possible. But according to a new study using data from NASA’s James Webb Space Telescope, it does not have an Earth-like atmosphere.
“Ultimately, we want to know if something like the environment we enjoy on Earth can exist elsewhere, and under what conditions. While NASA’s James Webb Space Telescope is giving us the ability to explore this question in Earth-sized planets for the first time, at this point we can rule out TRAPPIST-1 d from a list of potential Earth twins or cousins,” said Caroline Piaulet-Ghorayeb of the University of Chicago and Trottier Institute for Research on Exoplanets (IREx) at Université de Montréal, lead author of the study published in The Astrophysical Journal.
Planet TRAPPIST-1 d
The TRAPPIST-1 system is located 40 light-years away and was revealed as the record-holder for most Earth-sized rocky planets around a single star in 2017, thanks to data from NASA’s retired Spitzer Space Telescope and other observatories. Due to that star being a dim, relatively cold red dwarf, the “habitable zone” or “Goldilocks zone” – where the planet’s temperature may be just right, such that liquid surface water is possible – lies much closer to the star than in our solar system. TRAPPIST-1 d, the third planet from the red dwarf star, lies on the cusp of that temperate zone, yet its distance to its star is only 2 percent of Earth’s distance from the Sun. TRAPPIST-1 d completes an entire orbit around its star, its year, in only four Earth days.
Webb’s NIRSpec (Near-Infrared Spectrograph) instrument did not detect molecules from TRAPPIST-1 d that are common in Earth’s atmosphere, like water, methane, or carbon dioxide. However, Piaulet-Ghorayeb outlined several possibilities for the exoplanet that remain open for follow-up study.
“There are a few potential reasons why we don’t detect an atmosphere around TRAPPIST-1 d. It could have an extremely thin atmosphere that is difficult to detect, somewhat like Mars. Alternatively, it could have very thick, high-altitude clouds that are blocking our detection of specific atmospheric signatures — something more like Venus. Or, it could be a barren rock, with no atmosphere at all,” Piaulet-Ghorayeb said.
Image: TRAPPIST-1 d (Artist’s Concept)
This artist’s concept depicts planet TRAPPIST-1 d passing in front of its turbulent star, with other members of the closely packed system shown in the background. The TRAPPIST-1 system is intriguing to scientists for a few reasons. Not only does the system have seven Earth-sized rocky worlds, but its star is a red dwarf, the most common type of star in the Milky Way galaxy. If an Earth-sized world can maintain an atmosphere here, and thus have the potential for liquid surface water, the chance of finding similar worlds throughout the galaxy is much higher. In studying the TRAPPIST-1 planets, scientists are determining the best methods for separating starlight from potential atmospheric signatures in data from NASA’s James Webb Space Telescope. The star TRAPPIST-1’s variability, with frequent flares, provides a challenging testing ground for these methods. NASA, ESA, CSA, Joseph Olmsted (STScI) The Star TRAPPIST-1
No matter what the case may be for TRAPPIST-1 d, it’s tough being a planet in orbit around a red dwarf star. TRAPPIST-1, the host star of the system, is known to be volatile, often releasing flares of high-energy radiation with the potential to strip off the atmospheres of its small planets, especially those orbiting most closely. Nevertheless, scientists are motivated to seek signs of atmospheres on the TRAPPIST-1 planets because red dwarf stars are the most common stars in our galaxy. If planets can hold on to an atmosphere here, under waves of harsh stellar radiation, they could, as the saying goes, make it anywhere.
“Webb’s sensitive infrared instruments are allowing us to delve into the atmospheres of these smaller, colder planets for the first time,” said Björn Benneke of IREx at Université de Montréal, a co-author of the study. “We’re really just getting started using Webb to look for atmospheres on Earth-sized planets, and to define the line between planets that can hold onto an atmosphere, and those that cannot.”
The Outer TRAPPIST-1 Planets
Webb observations of the outer TRAPPIST-1 planets are ongoing, which hold both potential and peril. On the one hand, Benneke said, planets e, f, g, and h may have better chances of having atmospheres because they are further away from the energetic eruptions of their host star. However, their distance and colder environment will make atmospheric signatures more difficult to detect, even with Webb’s infrared instruments.
“All hope is not lost for atmospheres around the TRAPPIST-1 planets,” Piaulet-Ghorayeb said. “While we didn’t find a big, bold atmospheric signature at planet d, there is still potential for the outer planets to be holding onto a lot of water and other atmospheric components.”
“As NASA leads the way in searching for life outside our solar system, one of the most important avenues we can pursue is understanding which planets retain their atmospheres, and why,” said Shawn Domagal-Goldman, acting director of the Astrophysics Division at NASA Headquarters in Washington. “NASA’s James Webb Space Telescope has pushed our capabilities for studying exoplanet atmospheres further than ever before, beyond extreme worlds to some rocky planets – allowing us to begin confirming theories about the kind of planets that may be potentially habitable. This important groundwork will position our next missions, like NASA’s Habitable Worlds Observatory, to answer a universal question: Are we alone?”
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).
To learn more about Webb, visit:
https://science.nasa.gov/webb
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By European Space Agency
Astronomers using the NASA/ESA/CSA James Webb Space Telescope have found strong evidence of a giant planet orbiting a star in the stellar system closest to our own Sun. At just 4 light-years away from Earth, the Alpha Centauri triple star system has long been a compelling target in the search for worlds beyond our solar system.
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By NASA
Explore Webb Webb News Latest News Latest Images Webb’s Blog Awards X (offsite – login reqd) Instagram (offsite – login reqd) Facebook (offsite- login reqd) Youtube (offsite) Overview About Who is James Webb? Fact Sheet Impacts+Benefits FAQ Science Overview and Goals Early Universe Galaxies Over Time Star Lifecycle Other Worlds Observatory Overview Launch Deployment Orbit Mirrors Sunshield Instrument: NIRCam Instrument: MIRI Instrument: NIRSpec Instrument: FGS/NIRISS Optical Telescope Element Backplane Spacecraft Bus Instrument Module Multimedia About Webb Images Images Videos What is Webb Observing? 3d Webb in 3d Solar System Podcasts Webb Image Sonifications Webb’s First Images Team International Team People Of Webb More For the Media For Scientists For Educators For Fun/Learning 6 Min Read NASA’s Webb Finds New Evidence for Planet Around Closest Solar Twin
This artist’s concept shows what a gas giant orbiting Alpha Centauri A could look like. Observations of the triple star system Alpha Centauri using NASA’s James Webb Space Telescope indicate the potential gas giant, about the mass of Saturn, orbiting the star by about two times the distance between the Sun and Earth. Full illustration and caption shown below. Credits:
Artwork: NASA, ESA, CSA, STScI, R. Hurt (Caltech/IPAC) Astronomers using NASA’s James Webb Space Telescope have found strong evidence of a giant planet orbiting a star in the stellar system closest to our own Sun. At just 4 light-years away from Earth, the Alpha Centauri triple star system has long been a compelling target in the search for worlds beyond our solar system.
Visible only from Earth’s Southern hemisphere, it’s made up of the binary Alpha Centauri A and Alpha Centauri B, both Sun-like stars, and the faint red dwarf star Proxima Centauri. Alpha Centauri A is the third brightest star in the night sky. While there are three confirmed planets orbiting Proxima Centauri, the presence of other worlds surrounding Alpha Centauri A and Alpha Centauri B has proved challenging to confirm.
Now, Webb’s observations from its Mid-Infrared Instrument (MIRI) are providing the strongest evidence to date of a gas giant orbiting Alpha Centauri A. The results have been accepted in a series of two papers in The Astrophysical Journal Letters.
If confirmed, the planet would be the closest to Earth that orbits in the habitable zone of a Sun-like star. However, because the planet candidate is a gas giant, scientists say it would not support life as we know it.
“With this system being so close to us, any exoplanets found would offer our best opportunity to collect data on planetary systems other than our own. Yet, these are incredibly challenging observations to make, even with the world’s most powerful space telescope, because these stars are so bright, close, and move across the sky quickly,” said Charles Beichman, NASA’s Jet Propulsion Laboratory and the NASA Exoplanet Science Institute at Caltech’s IPAC astronomy center, co-first author on the new papers. “Webb was designed and optimized to find the most distant galaxies in the universe. The operations team at the Space Telescope Science Institute had to come up with a custom observing sequence just for this target, and their extra effort paid off spectacularly.”
Image A: Alpha Centauri 3 Panel (DSS, Hubble, Webb)
This image shows the Alpha Centauri star system from several different ground- and space-based observatories: the Digitized Sky Survey (DSS), NASA’s Hubble Space Telescope, and NASA’s James Webb Space Telescope. Alpha Centauri A is the third brightest star in the night sky, and the closest Sun-like star to Earth. The ground-based image from DSS shows the triple system as a single source of light, while Hubble resolves the two Sun-like stars in the system, Alpha Centauri A and Alpha Centauri B. The image from Webb’s MIRI (Mid-Infrared Instrument), which uses a coronagraphic mask to block the bright glare from Alpha Centauri A, reveals a potential planet orbiting the star. Science: NASA, ESA, CSA, STScI, DSS, A. Sanghi (Caltech), C. Beichman (NExScI, NASA/JPL-Caltech), D. Mawet (Caltech); Image Processing: J. DePasquale (STScI) Several rounds of meticulously planned observations by Webb, careful analysis by the research team, and extensive computer modeling helped determine that the source seen in Webb’s image is likely to be a planet, and not a background object (like a galaxy), foreground object (a passing asteroid), or other detector or image artifact.
The first observations of the system took place in August 2024, using the coronagraphic mask aboard MIRI to block Alpha Centauri A’s light. While extra brightness from the nearby companion star Alpha Centauri B complicated the analysis, the team was able to subtract out the light from both stars to reveal an object over 10,000 times fainter than Alpha Centauri A, separated from the star by about two times the distance between the Sun and Earth.
Image B: Alpha Centauri 3 Panel (Webb MIRI Image Detail)
This three-panel image captures NASA’s James Webb Space Telescope’s observational search for a planet around the nearest Sun-like star, Alpha Centauri A. The initial image shows the bright glare of Alpha Centauri A and Alpha Centauri B, and the middle panel then shows the system with a coronagraphic mask placed over Alpha Centauri A to block its bright glare. However, the way the light bends around the edges of the coronagraph creates ripples of light in the surrounding space. The telescope’s optics (its mirrors and support structures) cause some light to interfere with itself, producing circular and spoke-like patterns. These complex light patterns, along with light from the nearby Alpha Centauri B, make it incredibly difficult to spot faint planets. In the panel at the right, astronomers have subtracted the known patterns (using reference images and algorithms) to clean up the image and reveal faint sources like the candidate planet. Science: NASA, ESA, CSA, STScI, A. Sanghi (Caltech), C. Beichman (NExScI, NASA/JPL-Caltech), D. Mawet (Caltech); Image Processing: J. DePasquale (STScI) While the initial detection was exciting, the research team needed more data to come to a firm conclusion. However, additional observations of the system in February 2025 and April 2025 (using Director’s Discretionary Time) did not reveal any objects like the one identified in August 2024.
“We are faced with the case of a disappearing planet! To investigate this mystery, we used computer models to simulate millions of potential orbits, incorporating the knowledge gained when we saw the planet, as well as when we did not,” said PhD student Aniket Sanghi of Caltech in Pasadena, California. Sanghi is a co-first author on the two papers covering the team’s research.
In these simulations, the team took into account both a 2019 sighting of the potential exoplanet candidate by the European Southern Observatory’s Very Large Telescope, the new data from Webb, and considered orbits that would be gravitationally stable in the presence of Alpha Centauri B, meaning the planet wouldn’t get flung out of the system.
Researchers say a non-detection in the second and third round of observations with Webb isn’t surprising.
“We found that in half of the possible orbits simulated, the planet moved too close to the star and wouldn’t have been visible to Webb in both February and April 2025,” said Sanghi.
Image C: Alpha Centauri A Planet Candidate (Artist’s Concept)
This artist’s concept shows what a gas giant orbiting Alpha Centauri A could look like. Observations of the triple star system Alpha Centauri using NASA’s James Webb Space Telescope indicate the potential gas giant, about the mass of Saturn, orbiting the star by about two times the distance between the Sun and Earth. In this concept, Alpha Centauri A is depicted at the upper left of the planet, while the other Sun-like star in the system, Alpha Centauri B, is at the upper right. Our Sun is shown as a small dot of light between those two stars. Artwork: NASA, ESA, CSA, STScI, R. Hurt (Caltech/IPAC) Based on the brightness of the planet in the mid-infrared observations and the orbit simulations, researchers say it could be a gas giant approximately the mass of Saturn orbiting Alpha Centauri A in an elliptical path varying between 1 to 2 times the distance between Sun and Earth.
“If confirmed, the potential planet seen in the Webb image of Alpha Centauri A would mark a new milestone for exoplanet imaging efforts,” Sanghi says. “Of all the directly imaged planets, this would be the closest to its star seen so far. It’s also the most similar in temperature and age to the giant planets in our solar system, and nearest to our home, Earth,” he says. “Its very existence in a system of two closely separated stars would challenge our understanding of how planets form, survive, and evolve in chaotic environments.”
If confirmed by additional observations, the team’s results could transform the future of exoplanet science.
“This would become a touchstone object for exoplanet science, with multiple opportunities for detailed characterization by Webb and other observatories,” said Beichman.
For example, NASA’s Nancy Grace Roman Space Telescope, set to launch by May 2027 and potentially as early as fall 2026, is equipped with dedicated hardware that will test new technologies to observe binary systems like Alpha Centauri in search of other worlds. Roman’s visible light data would complement Webb’s infrared observations, yielding unique insights on the size and reflectivity of the planet.
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).
To learn more about Webb, visit:
https://science.nasa.gov/webb
Downloads
Click any image to open a larger version.
View/Download all image products at all resolutions for this article from the Space Telescope Science Institute.
View/Download the science paper by C. Beichman et al.
View/Download the science paper by A. Sanghi et al.
Media Contacts
Laura Betz – laura.e.betz@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Hannah Braun – hbraun@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
Related Information
Video: How to Study Exoplanets: Webb and Challenges
Webb Blog: NASA’s Webb Takes Its First-Ever Direct Image of Distant World
Webb Blog: How Webb’s Coronagraphs Reveal Exoplanets in the Infrared
Video: Eclipse/Coronagraph Animation
More Webb News
More Webb Images
Webb Science Themes
Webb Mission Page
Related For Kids
What is the Webb Telescope?
SpacePlace for Kids
En Español
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James Webb Space Telescope
Webb is the premier observatory of the next decade, serving thousands of astronomers worldwide. It studies every phase in the…
Exoplanets
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Last Updated Aug 07, 2025 Editor Marty McCoy Contact Laura Betz laura.e.betz@nasa.gov Related Terms
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By NASA
Explore Hubble Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Hubble and Artificial Intelligence Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts Multimedia Images Videos Sonifications Podcasts e-Books Online Activities 3D Hubble Models Lithographs Fact Sheets Posters Hubble on the NASA App Glossary News Hubble News Social Media Media Resources More 35th Anniversary Online Activities 6 Min Read NASA’s Hubble, Chandra Spot Rare Type of Black Hole Eating a Star
NASA’s Hubble Space Telescope and NASA’s Chandra X-ray Observatory team up to identify a possible intermediate-mass black hole. Credits:
NASA, ESA, CXC, Yi-Chi Chang (National Tsing Hua University); Image Processing: Joseph DePasquale (STScI) NASA’s Hubble Space Telescope and NASA’s Chandra X-ray Observatory have teamed up to identify a new possible example of a rare class of black holes. Called NGC 6099 HLX-1, this bright X-ray source seems to reside in a compact star cluster in a giant elliptical galaxy.
Just a few years after its 1990 launch, Hubble discovered that galaxies throughout the universe can contain supermassive black holes at their centers weighing millions or billions of times the mass of our Sun. In addition, galaxies also contain as many as millions of small black holes weighing less than 100 times the mass of the Sun. These form when massive stars reach the end of their lives.
Far more elusive are intermediate-mass black holes (IMBHs), weighing between a few hundred to a few 100,000 times the mass of our Sun. This not-too-big, not-too-small category of black holes is often invisible to us because IMBHs don’t gobble as much gas and stars as the supermassive ones, which would emit powerful radiation. They have to be caught in the act of foraging in order to be found. When they occasionally devour a hapless bypassing star — in what astronomers call a tidal disruption event— they pour out a gusher of radiation.
The newest probable IMBH, caught snacking in telescope data, is located on the galaxy NGC 6099’s outskirts at approximately 40,000 light-years from the galaxy’s center, as described in a new study in the Astrophysical Journal. The galaxy is located about 450 million light-years away in the constellation Hercules.
A Hubble Space Telescope image of a pair of galaxies: NGC 6099 (lower left) and NGC 6098 (upper right). The purple blob depicts X-ray emission from a compact star cluster. The X-rays are produced by an intermediate-mass black hole tearing apart a star. Science: NASA, ESA, CXC, Yi-Chi Chang (National Tsing Hua University); Image Processing: Joseph DePasquale (STScI) Astronomers first saw an unusual source of X-rays in an image taken by Chandra in 2009. They then followed its evolution with ESA’s XMM-Newton space observatory.
“X-ray sources with such extreme luminosity are rare outside galaxy nuclei and can serve as a key probe for identifying elusive IMBHs. They represent a crucial missing link in black hole evolution between stellar mass and supermassive black holes,” said lead author Yi-Chi Chang of the National Tsing Hua University, Hsinchu, Taiwan.
X-ray emission coming from NGC 6099 HLX-1 has a temperature of 3 million degrees, consistent with a tidal disruption event. Hubble found evidence for a small cluster of stars around the black hole. This cluster would give the black hole a lot to feast on, because the stars are so closely crammed together that they are just a few light-months apart (about 500 billion miles).
The suspected IMBH reached maximum brightness in 2012 and then continued declining to 2023. The optical and X-ray observations over the period do not overlap, so this complicates the interpretation. The black hole may have ripped apart a captured star, creating a plasma disk that displays variability, or it may have formed a disk that flickers as gas plummets toward the black hole.
“If the IMBH is eating a star, how long does it take to swallow the star’s gas? In 2009, HLX-1 was fairly bright. Then in 2012, it was about 100 times brighter. And then it went down again,” said study co-author Roberto Soria of the Italian National Institute for Astrophysics (INAF). “So now we need to wait and see if it’s flaring multiple times, or there was a beginning, there was peak, and now it’s just going to go down all the way until it disappears.”
The IMBH is on the outskirts of the host galaxy, NGC 6099, about 40,000 light-years from the galaxy’s center. There is presumably a supermassive black hole at the galaxy’s core, which is currently quiescent and not devouring a star.
Black Hole Building Blocks
The team emphasizes that doing a survey of IMBHs can reveal how the larger supermassive black holes form in the first place. There are two alternative theories. One is that IMBHs are the seeds for building up even larger black holes by coalescing together, since big galaxies grow by taking in smaller galaxies. The black hole in the middle of a galaxy grows as well during these mergers. Hubble observations uncovered a proportional relationship: the more massive the galaxy, the bigger the black hole. The emerging picture with this new discovery is that galaxies could have “satellite IMBHs” that orbit in a galaxy’s halo but don’t always fall to the center.
Another theory is that the gas clouds in the middle of dark-matter halos in the early universe don’t make stars first, but just collapse directly into a supermassive black hole. NASA’s James Webb Space Telescope’s discovery of very distant black holes being disproportionately more massive relative to their host galaxy tends to support this idea.
However, there could be an observational bias toward the detection of extremely massive black holes in the distant universe, because those of smaller size are too faint to be seen. In reality, there could be more variety out there in how our dynamic universe constructs black holes. Supermassive black holes collapsing inside dark-matter halos might simply grow in a different way from those living in dwarf galaxies where black-hole accretion might be the favored growth mechanism.
“So if we are lucky, we’re going to find more free-floating black holes suddenly becoming X-ray bright because of a tidal disruption event. If we can do a statistical study, this will tell us how many of these IMBHs there are, how often they disrupt a star, how bigger galaxies have grown by assembling smaller galaxies.” said Soria.
The challenge is that Chandra and XMM-Newton only look at a small fraction of the sky, so they don’t often find new tidal disruption events, in which black holes are consuming stars. The Vera C. Rubin Observatory in Chile, an all-sky survey telescope from the U.S. National Science Foundation and the Department of Energy, could detect these events in optical light as far as hundreds of millions of light-years away. Follow-up observations with Hubble and Webb can reveal the star cluster around the black hole.
The Hubble Space Telescope has been operating for more than three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Related Images & Videos
NGC 6099 (Hubble + Chandra)
A Hubble Space Telescope image of a pair of galaxies: NGC 6099 (lower left) and NGC 6098 (upper right). The purple blob depicts X-ray emission from a compact star cluster. The X-rays are produced by an intermediate-mass black hole tearing apart a star.
NGC 6099 (Hubble)
A Hubble Space Telescope image of a pair of galaxies: NGC 6099 (lower left) and NGC 6098 (upper right). The white dot labeled HLX-1 is the visible-light component of the location of a compact star cluster where an intermediate-mass black hole is tearing apart a star.
NGC 6099 Compass Image
This compass image shows two elliptical galaxies, NGC 6098 at upper right and NGC 6099 at lower left. The fuzzy purple blob at bottom center shows X-ray emission produced by an intermediate-mass black hole tearing apart a star.
HLX-1 Illustration
This sequence of artistic illustrations, from upper left to bottom right, shows how a black hole in the core of a star cluster captures a bypassing star and gravitationally shreds it until there is an explosion, seen in the outskirts of the host galaxy.
HLX-1 Animation
This video is an illustration of an intermediate-mass black hole capturing and gravitationally shredding a star. It begins by zooming into a pair of galaxies. The galaxy at lower left, NGC 6099, contain a dense star cluster at center. The video then zooms into the heart of the cl…
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Last Updated Jul 24, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Contact Media Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
Ray Villard
Space Telescope Science Institute
Baltimore, Maryland
Related Terms
Hubble Space Telescope Astrophysics Astrophysics Division Black Holes Chandra X-Ray Observatory Galaxies Goddard Space Flight Center Marshall Astrophysics Marshall Space Flight Center
Related Links and Documents
Chinese translation of release Science Paper: Multiwavelength Study of a Hyperluminous X-Ray Source near NGC6099: A Strong IMBH Candidate, PDF (1.81 MB)
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