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5 Min Read Webb Maps Full Picture of How Phoenix Galaxy Cluster Forms Stars
Spectroscopic data collected from NASA’s James Webb Space Telescope is overlayed on an image of the Phoenix cluster that combines data from NASA’s Hubble Space Telescope, Chandra X-ray Observatory and the Very Large Array (VLA) radio telescope. Credits:
NASA, CXC, NRAO, ESA, M. McDonald (MIT), M. Reefe (MIT), J. Olmsted (STScI) Discovery proves decades-old theory of galaxy feeding cycle.
Researchers using NASA’s James Webb Space Telescope have finally solved the mystery of how a massive galaxy cluster is forming stars at such a high rate. The confirmation from Webb builds on more than a decade of studies using NASA’s Chandra X-ray Observatory and Hubble Space Telescope, as well as several ground-based observatories.
The Phoenix cluster, a grouping of galaxies bound together by gravity 5.8 billion light-years from Earth, has been a target of interest for astronomers due to a few unique properties. In particular, ones that are surprising: a suspected extreme cooling of gas and a furious star formation rate despite a roughly 10 billion solar mass supermassive black hole at its core. In other observed galaxy clusters, the central supermassive black hole powers energetic particles and radiation that prevents gas from cooling enough to form stars. Researchers have been studying gas flows within this cluster to try to understand how it is driving such extreme star formation.
Image A: Phoenix Cluster (Hubble, Chandra, VLA Annotated)
Spectroscopic data collected from NASA’s James Webb Space Telescope is overlayed on an image of the Phoenix cluster that combines data from NASA’s Hubble Space Telescope, Chandra X-ray Observatory and the Very Large Array (VLA) radio telescope. Webb’s powerful sensitivity in the mid-infrared detected the cooling gas that leads to a furious rate of star formation in this massive galaxy cluster. Credit: NASA, CXC, NRAO, ESA, M. McDonald (MIT), M. Reefe (MIT), J. Olmsted (STScI) “We can compare our previous studies of the Phoenix cluster, which found differing cooling rates at different temperatures, to a ski slope,” said Michael McDonald of the Massachusetts Institute of Technology in Cambridge, principal investigator of the program. “The Phoenix cluster has the largest reservoir of hot, cooling gas of any galaxy cluster — analogous to having the busiest chair lift, bringing the most skiers to the top of the mountain. However, not all of those skiers were making it down the mountain, meaning not all the gas was cooling to low temperatures. If you had a ski slope where there were significantly more people getting off the ski lift at the top than were arriving at the bottom, that would be a problem!”
To date, in the Phoenix cluster, the numbers weren’t adding up, and researchers were missing a piece of the process. Webb has now found those proverbial skiers at the middle of the mountain, in that it has tracked and mapped the missing cooling gas that will ultimately feed star formation. Most importantly, this intermediary warm gas was found within cavities tracing the very hot gas, a searing 18 million degrees Fahrenheit, and the already cooled gas around 18,000 degrees Fahrenheit.
The team studied the cluster’s core in more detail than ever before with the Medium-Resolution Spectrometer on Webb’s Mid-Infrared Instrument (MIRI). This tool allows researchers to take two-dimenstional spectroscopic data from a region of the sky, during one set of observations.
“Previous studies only measured gas at the extreme cold and hot ends of the temperature distribution throughout the center of the cluster,” added McDonald. “We were limited — it was not possible to detect the ‘warm’ gas that we were looking for. With Webb, we could do this for the first time.”
Image B: Phoenix Cluster (Hubble, Chandra, VLA)
This image of the Phoenix cluster combines data from NASA’s Hubble Space Telescope, Chandra X-ray Observatory, and the Very Large Array radio telescope. X-rays from Chandra depict extremely hot gas in purple. Optical light data from Hubble show galaxies in yellow, and filaments of cooler gas where stars are forming in light blue. Outburst generated jets, represented in red, are seen in radio waves by the VLA radio telescope. NASA, CXC, NRAO, ESA, M. McDonald (MIT). A Quirk of Nature
Webb’s capability to detect this specific temperature of cooling gas, around 540,000 degrees Fahrenheit, is in part due to its instrumental capabilities. However, the researchers are getting a little help from nature, as well.
This oddity involves two very different ionized atoms, neon and oxygen, created in similar environments. At these temperatures, the emission from oxygen is 100 times brighter but is only visible in ultraviolet. Even though the neon is much fainter, it glows in the infrared, which allowed the researchers to take advantage of Webb’s advanced instruments.
“In the mid-infrared wavelengths detected by Webb, the neon VI signature was absolutely booming,” explained Michael Reefe, also of the Massachusetts Institute of Technology, lead author on the paper published in Nature. “Even though this emission is usually more difficult to detect, Webb’s sensitivity in the mid-infrared cuts through all of the noise.”
The team now hopes to employ this technique to study more typical galaxy clusters. While the Phoenix cluster is unique in many ways, this proof of concept is an important step towards learning about how other galaxy clusters form stars.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).
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Laura Betz – laura.e.betz@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Space Telescope Science Institute, Baltimore, Md.
Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
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By European Space Agency
This new NASA/ESA/CSA James Webb Space Telescope Picture of the Month presents HH 30 in unprecedented detail. This target is an edge-on protoplanetary disc that is surrounded by jets and a disc wind, and is located in the dark cloud LDN 1551 in the Taurus Molecular Cloud.
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By European Space Agency
The first IRIDE satellite – the Pathfinder Hawk – is now in orbit around Earth after lifting off on a SpaceX Falcon 9 rocket from the Vandenberg Space Force Base in California on 14 January.
As its ‘Pathfinder’ name suggests, this new microsatellite is a prototype for one of the six IRIDE constellations, which are tailored to provide information for a wide range of environmental, emergency and security services for Italy.
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By NASA
Webb Webb News Latest News Latest Images Blog (offsite) 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 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 Team International Team People Of Webb More For the Media For Scientists For Educators For Fun/Learning 6 Min Read NASA’s Webb Reveals Intricate Layers of Interstellar Dust, Gas
This shimmering cosmic curtain shows interstellar gas and dust that has been heated by the flashbulb explosion of a long-ago supernova. The gas then glows infrared light in what is known as a thermal light echo. As the supernova illumination travels through space at the speed of light, the echo appears to expand. NASA’s James Webb Space Telescope observed this light echo in the vicinity of the supernova remnant Cassiopeia A. Credits:
NASA, ESA, CSA, STScI, J. Jencson (Caltech/IPAC) Once upon a time, the core of a massive star collapsed, creating a shockwave that blasted outward, ripping the star apart as it went. When the shockwave reached the star’s surface, it punched through, generating a brief, intense pulse of X-rays and ultraviolet light that traveled outward into the surrounding space. About 350 years later, that pulse of light has reached interstellar material, illuminating it, warming it, and causing it to glow in infrared light.
NASA’s James Webb Space Telescope has observed that infrared glow, revealing fine details resembling the knots and whorls of wood grain. These observations are allowing astronomers to map the true 3D structure of this interstellar dust and gas (known as the interstellar medium) for the first time.
“We were pretty shocked to see this level of detail,” said Jacob Jencson of Caltech/IPAC in Pasadena, principal investigator of the science program.
“We see layers like an onion,” added Josh Peek of the Space Telescope Science Institute in Baltimore, a member of the science team. “We think every dense, dusty region that we see, and most of the ones we don’t see, look like this on the inside. We just have never been able to look inside them before.”
The team is presenting their findings in a press conference at the 245th meeting of the American Astronomical Society in Washington.
“Even as a star dies, its light endures—echoing across the cosmos. It’s been an extraordinary three years since we launched NASA’s James Webb Space Telescope. Every image, every discovery, shows a portrait not only of the majesty of the universe but the power of the NASA team and the promise of international partnerships. This groundbreaking mission, NASA’s largest international space science collaboration, is a true testament to NASA’s ingenuity, teamwork, and pursuit of excellence,” said NASA Administrator Bill Nelson. “What a privilege it has been to oversee this monumental effort, shaped by the tireless dedication of thousands of scientists and engineers around the globe. This latest image beautifully captures the lasting legacy of Webb—a keyhole into the past and a mission that will inspire generations to come.”
Image A: Light Echoes Near Cassiopeia A (NIRCam)
These shimmering cosmic curtains show interstellar gas and dust that has been heated by the flashbulb explosion of a long-ago supernova. The gas then glows infrared light in what is known as a thermal light echo. As the supernova illumination travels through space at the speed of light, the echo appears to expand. NASA’s James Webb Space Telescope observed this light echo in the vicinity of the supernova remnant Cassiopeia A three separate times, in essence creating a 3D scan of the interstellar material. Note that the field of view in the top row is rotated slightly clockwise relative to the middle and bottom rows, due to the roll angle of the Webb telescope when the observations were taken. NASA, ESA, CSA, STScI, J. Jencson (Caltech/IPAC) Video A: Light Echoes Near Cassiopeia A (NIRCam)
This time-lapse video using data from NASA’s James Webb Space Telescope highlights the evolution of one light echo in the vicinity of the supernova remnant Cassiopeia A. A light echo is created when a star explodes or erupts, flashing light into surrounding clumps of interstellar dust and causing them to shine in an ever-expanding pattern. Webb’s exquisite resolution not only shows incredible detail within these light echoes, but also shows their expansion over the course of just a few weeks – a remarkably short timescale considering that most cosmic targets remain unchanged over a human lifetime.
Credit: NASA, ESA, CSA, STScI, J. Jencson (Caltech/IPAC) Taking a CT Scan
The images from Webb’s NIRCam (Near-Infrared Camera) highlight a phenomenon known as a light echo. A light echo is created when a star explodes or erupts, flashing light into surrounding clumps of dust and causing them to shine in an ever-expanding pattern. Light echoes at visible wavelengths (such as those seen around the star V838 Monocerotis) are due to light reflecting off of interstellar material. In contrast, light echoes at infrared wavelengths are caused when the dust is warmed by energetic radiation and then glows.
The researchers targeted a light echo that had previously been observed by NASA’s retired Spitzer Space Telescope. It is one of dozens of light echoes seen near the Cassiopeia A supernova remnant – the remains of the star that exploded. The light echo is coming from unrelated material that is behind Cassiopeia A, not material that was ejected when the star exploded.
The most obvious features in the Webb images are tightly packed sheets. These filaments show structures on remarkably small scales of about 400 astronomical units, or less than one-hundredth of a light-year. (An astronomical unit, or AU, is the average Earth-Sun distance. Neptune’s orbit is 60 AU in diameter.)
“We did not know that the interstellar medium had structures on that small of a scale, let alone that it was sheet-like,” said Peek.
These sheet-like structures may be influenced by interstellar magnetic fields. The images also show dense, tightly wound regions that resemble knots in wood grain. These may represent magnetic “islands” embedded within the more streamlined magnetic fields that suffuse the interstellar medium.
“This is the astronomical equivalent of a medical CT scan,” explained Armin Rest of the Space Telescope Science Institute, a member of the science team. “We have three slices taken at three different times, which will allow us to study the true 3D structure. It will completely change the way we study the interstellar medium.”
Image B: Cassiopeia A (Spitzer with Webb Insets)
This background image of the region around supernova remnant Cassiopeia A was released by NASA’s Spitzer Space Telescope in 2008. By taking multiple images of this region over three years with Spitzer, researchers were able to examine a number of light echoes. Now, NASA’s James Webb Space Telescope has imaged some of these light echoes in much greater detail. Insets at lower right show one epoch of Webb observations, while the inset at left shows a Webb image of the central supernova remnant released in 2023. Spitzer Image: NASA/JPL-Caltech/Y. Kim (Univ. of Arizona/Univ. of Chicago). Cassiopeia A Inset: NASA, ESA, CSA, STScI, Danny Milisavljevic (Purdue University), Ilse De Looze (UGent), Tea Temim (Princeton University). Light Echoes Inset: NASA, ESA, CSA, STScI, J. Jencson (Caltech/IPAC). Future Work
The team’s science program also includes spectroscopic observations using Webb’s MIRI (Mid-Infrared Instrument). They plan to target the light echo multiple times, weeks or months apart, to observe how it evolves as the light echo passes by.
“We can observe the same patch of dust before, during, and after it’s illuminated by the echo and try to look for any changes in the compositions or states of the molecules, including whether some molecules or even the smallest dust grains are destroyed,” said Jencson.
Infrared light echoes are also extremely rare, since they require a specific type of supernova explosion with a short pulse of energetic radiation. NASA’s upcoming Nancy Grace Roman Space Telescope will conduct a survey of the galactic plane that may find evidence of additional infrared light echoes for Webb to study in detail.
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).
Downloads
Right click any image to save it or open a larger version in a new tab/window via the browser’s popup menu.
View/Download all image products at all resolutions for this article from the Space Telescope Science Institute.
Media Contacts
Laura Betz – laura.e.betz@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
Science – Jacob Jencson (Caltech/IPAC)
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Articles: Past Webb news releases on Cassiopeia A
Interactive: Explore light echoes in V838 Monocerotis
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Last Updated Jan 14, 2025 Editor Marty McCoy Contact Laura Betz laura.e.betz@nasa.gov Related Terms
Astrophysics Goddard Space Flight Center James Webb Space Telescope (JWST) Nebulae Science & Research Supernova Remnants Supernovae The Universe View the full article
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Webb Webb News Latest News Latest Images Blog (offsite) 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 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 Team International Team People Of Webb More For the Media For Scientists For Educators For Fun/Learning 6 Min Read Newfound Galaxy Class May Indicate Early Black Hole Growth, Webb Finds
A team of astronomers sifted through James Webb Space Telescope data from multiple surveys to compile one of the largest samples of “little red dots” to date. Credits:
NASA, ESA, CSA, STScI, Dale Kocevski (Colby College). In December 2022, less than six months after commencing science operations, NASA’s James Webb Space Telescope revealed something never seen before: numerous red objects that appear small on the sky, which scientists soon called “little red dots” (LRDs). Though these dots are quite abundant, researchers are perplexed by their nature, the reason for their unique colors, and what they convey about the early universe.
A team of astronomers recently compiled one of the largest samples of LRDs to date, nearly all of which existed during the first 1.5 billion years after the big bang. They found that a large fraction of the LRDs in their sample showed signs of containing growing supermassive black holes.
“We’re confounded by this new population of objects that Webb has found. We don’t see analogs of them at lower redshifts, which is why we haven’t seen them prior to Webb,” said Dale Kocevski of Colby College in Waterville, Maine, and lead author of the study. “There’s a substantial amount of work being done to try to determine the nature of these little red dots and whether their light is dominated by accreting black holes.”
Image A: Little Red Dots (NIRCam Image)
A team of astronomers sifted through James Webb Space Telescope data from multiple surveys to compile one of the largest samples of “little red dots” to date. From their sample, they found that these mysterious red objects that appear small on the sky emerge in large numbers around 600 million years after the big bang and undergo a rapid decline in quantity around 1.5 billion years after the big bang. NASA, ESA, CSA, STScI, Dale Kocevski (Colby College). A Potential Peek Into Early Black Hole Growth
A significant contributing factor to the team’s large sample size of LRDs was their use of publicly available Webb data. To start, the team searched for these red sources in the Cosmic Evolution Early Release Science (CEERS) survey before widening their scope to other extragalactic legacy fields, including the JWST Advanced Deep Extragalactic Survey (JADES) and the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) survey.
The methodology used to identify these objects also differed from previous studies, resulting in the census spanning a wide redshift range. The distribution they discovered is intriguing: LRDs emerge in large numbers around 600 million years after the big bang and undergo a rapid decline in quantity around 1.5 billion years after the big bang.
The team looked toward the Red Unknowns: Bright Infrared Extragalactic Survey (RUBIES) for spectroscopic data on some of the LRDs in their sample. They found that about 70 percent of the targets showed evidence for gas rapidly orbiting 2 million miles per hour (1,000 kilometers per second) – a sign of an accretion disk around a supermassive black hole. This suggests that many LRDs are accreting black holes, also known as active galactic nuclei (AGN).
“The most exciting thing for me is the redshift distributions. These really red, high-redshift sources basically stop existing at a certain point after the big bang,” said Steven Finkelstein, a co-author of the study at the University of Texas at Austin. “If they are growing black holes, and we think at least 70 percent of them are, this hints at an era of obscured black hole growth in the early universe.”
Contrary to Headlines, Cosmology Isn’t Broken
When LRDs were first discovered, some suggested that cosmology was “broken.” If all of the light coming from these objects was from stars, it implied that some galaxies had grown so big, so fast, that theories could not account for them.
The team’s research supports the argument that much of the light coming from these objects is from accreting black holes and not from stars. Fewer stars means smaller, more lightweight galaxies that can be understood by existing theories.
“This is how you solve the universe-breaking problem,” said Anthony Taylor, a co-author of the study at the University of Texas at Austin.
Curiouser and Curiouser
There is still a lot up for debate as LRDs seem to evoke even more questions. For example, it is still an open question as to why LRDs do not appear at lower redshifts. One possible answer is inside-out growth: As star formation within a galaxy expands outward from the nucleus, less gas is being deposited by supernovas near the accreting black hole, and it becomes less obscured. In this case, the black hole sheds its gas cocoon, becomes bluer and less red, and loses its LRD status.
Additionally, LRDs are not bright in X-ray light, which contrasts with most black holes at lower redshifts. However, astronomers know that at certain gas densities, X-ray photons can become trapped, reducing the amount of X-ray emission. Therefore, this quality of LRDs could support the theory that these are heavily obscured black holes.
The team is taking multiple approaches to understand the nature of LRDs, including examining the mid-infrared properties of their sample, and looking broadly for accreting black holes to see how many fit LRD criteria. Obtaining deeper spectroscopy and select follow-up observations will also be beneficial for solving this currently “open case” about LRDs.
“There’s always two or more potential ways to explain the confounding properties of little red dots,” said Kocevski. “It’s a continuous exchange between models and observations, finding a balance between what aligns well between the two and what conflicts.”
These results were presented in a press conference at the 245th meeting of the American Astronomical Society in National Harbor, Maryland, and have been submitted for publication in The Astrophysical Journal.
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).
Downloads
Right click any image to save it or open a larger version in a new tab/window via the browser’s popup menu.
View/Download all image products at all resolutions for this article from the Space Telescope Science Institute.
Media Contacts
Laura Betz – laura.e.betz@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Abigail Major – amajor@stsci.edu, Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
Science – Dale Kocevski (Colby College)
Related Information
3D visualization: CEERS Fly Through visualization and JADES GOODS South Fly Through visualization
Graphic: What is cosmological redshift?
Graphic: Dissecting Supermassive Black Holes
Article: Webb Science: Galaxies Through Time
Web Page: Learn more about black holes
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Last Updated Jan 14, 2025 Editor Stephen Sabia Contact Laura Betz laura.e.betz@nasa.gov Related Terms
Astrophysics Black Holes Galaxies Galaxies, Stars, & Black Holes Goddard Space Flight Center James Webb Space Telescope (JWST) Science & Research Supermassive Black Holes The Universe View the full article
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