weic2604 — Science Release
Webb locates former star that exploded as supernova
Webb shows star was surrounded by a vast shell of carbon-rich dust
23 February 2026
For the first time, astronomers have used images from the NASA/ESA/CSA James Webb Space Telescope to identify a supernova progenitor that could not be seen by any other telescope: a red supergiant that was located in a nearby galaxy. The supergiant’s surroundings were surprisingly dusty - dusty enough to render it invisible to the NASA/ESA Hubble Space Telescope.
Forty million years ago, a star in a nearby galaxy exploded, spewing material across space and generating a brilliant beacon of light. That light traveled across the cosmos, reaching Earth on 29 June 2025, where it was detected by the All-Sky Automated Survey for Supernovae. Astronomers immediately turned their resources to this new supernova, designated 2025pht, to learn more about it. But one team of scientists instead turned to archives, seeking to use pre-supernova images to identify exactly which star among many had exploded. And they succeeded.
Images of galaxy NGC 1637 taken by the James Webb Space Telescope showed a single red supergiant star located exactly where the supernova now shines. This represents the first published detection of a supernova progenitor by Webb. The results were published in the Astrophysical Journal Letters.
“We’ve been waiting for this to happen – for a supernova to explode in a galaxy that Webb had already observed. We combined Hubble and Webb data sets to completely characterize this star for the first time,” said lead author Charlie Kilpatrick of Northwestern University in the United States.
The case of the missing red supergiants
By carefully aligning Hubble and Webb images taken of NGC 1637, the team was able to identify the progenitor star in images taken by Webb’s MIRI (Mid-Infrared Instrument) and NIRCam (Near-Infrared Camera) in 2024. They found that the star appeared surprisingly red – an indication that it was surrounded by dust that blocked shorter, bluer wavelengths of light.
“It’s the reddest, most dusty red supergiant that we’ve seen explode as a supernova,” said graduate student and co-author Aswin Suresh of Northwestern University.
This excess of dust could help explain a long-standing problem in astronomy that could be described as the case of the missing red supergiants. Astronomers expect the most massive stars that explode as supernovas to also be the brightest and most luminous. So, they should be easy to identify in pre-supernova images. However, that hasn’t been the case.
One potential explanation is that the most massive aging stars are also the dustiest. If they’re surrounded by large quantities of dust, their light could be dimmed to the point of undetectability. The Webb observations of supernova 2025pht support that hypothesis.
“I’ve been arguing in favor of that interpretation, but even I didn’t expect to see it as extreme as it was for supernova 2025pht. It would explain why these more massive supergiants are missing because they tend to be more dusty,” said Kilpatrick.
Carbon “burps”
The team was not only surprised by the amount of dust, but also by its composition. Applying computer models to the Webb observations indicated that the dust is likely carbon-rich, when astronomers would have expected it to be more silicate-rich. The team speculates that this carbon might have been dredged up from the star’s interior shortly before it exploded.
“Having observations in the mid-infrared was key to constraining what kind of dust we were seeing,” added Suresh.
The team now is working to look for similar red supergiants that may explode as supernovas in the future.
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: Image: NASA, ESA, CSA, STScI, C. Kilpatrick (Northwestern), A. Suresh (Northwestern); Image Processing: J. DePasquale (STScI)
Links
Contacts
Bethany Downer
ESA/Webb Chief Science Communications Officer
Email: [email protected]
ESA Newsroom and Media Relations Office
Email: [email protected]
About the Release
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