Using the NASA/ESA/CSA James Webb Space Telescope, astronomers have for the first time identified the progenitor of a nearby supernova — a red supergiant star cloaked in thick, dust-rich shrouds that made it invisible to previous observatories.
The main image at left shows a combined Webb and Hubble view of the spiral galaxy NGC 1637, with the region of interest in the top right; the remaining three panels show a detailed view of a red supergiant star before and after it exploded; the star is not visible in the Hubble image before the SN 2025pht explosion, but appears in the Webb image; the July 2025 view from Hubble shows the glowing aftermath of the explosion. Image credit: NASA / ESA / CSA / STScI / C. Kilpatrick, Northwestern / A. Suresh, Northwestern / J. DePasquale, STScI.
The supernova event in question, designated SN 2025pht, was discovered in NGC 1637 on June 29, 2025.
Astronomers immediately turned their resources to this supernova to learn more about it.
But Northwestern University astronomer Charlie Kilpatrick and his colleagues instead turned to archives, seeking to use pre-supernova images to identify exactly which star among many had exploded.
The images of NGC 1637 taken by Webb’s MIRI (Mid-Infrared Instrument) and NIRCam (Near-Infrared Camera) in 2024 showed a single red supergiant star located exactly where the supernova now shines.
“We’ve been waiting for this to happen — for a supernova to explode in a galaxy that Webb had already observed,” Dr. Kilpatrick said.
“We combined Hubble and Webb data sets to completely characterize this star for the first time.”
“It’s the reddest, most dusty red supergiant that we’ve seen explode as a supernova,” said Aswin Suresh, a graduate student at 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 supernovae 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 SN 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 SN 2025pht,” Dr. Kilpatrick said.
“It would explain why these more massive supergiants are missing because they tend to be more dusty.”
The authors also found that the dust surrounding the star is likely rich in carbon — an unexpected result, since scientists would normally anticipate silicate-dominated dust in such an environment.
They speculate 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,” Suresh said.
The team’s paper was published In October 2025 in the Astrophysical Journal Letters.
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Charles D. Kilpatrick et al. 2025. The Type II SN 2025pht in NGC 1637: A Red Supergiant with Carbon-rich Circumstellar Dust as the First JWST Detection of a Supernova Progenitor Star. ApJL 992, L10; doi: 10.3847/2041-8213/ae04de
