Using the NASA/ESA/CSA James Webb Space Telescope, astronomers have identified for the first time a nearby supernova, a red supergiant star shrouded in a thick dusty shroud not visible to previous observatories.
The main image on the left shows a combined Webb and Hubble view of spiral galaxy NGC 1637, with the region of interest visible in the upper right. The remaining three panels show detailed views of the red supergiant before and after the explosion. This star is not visible in the Hubble image before the SN 2025pht explosion, but it appears in the Web image. A 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, called SN 2025pht, was discovered in NGC 1637 on June 29, 2025.
Astronomers immediately poured resources into this supernova to learn more about it.
But Northwestern University astronomer Charlie Kilpatrick and his colleagues instead turned to the archives, using pre-supernova images to try to pinpoint which of the many stars exploded.
An image of NGC 1637 taken by Webb’s MIRI (Mid-Infrared Instrument) and NIRCam (Near-Infrared Camera) in 2024 shows a single red supergiant star located in the exact spot where the supernova is currently shining.
“We were waiting for this to happen. We were waiting for a supernova to explode in a galaxy that Webb was already observing,” Dr. Kilpatrick said.
“We combined the Hubble and Webb datasets to reveal the star’s complete characteristics for the first time.”
“This is the reddest, dustiest red supergiant we’ve ever seen explode as a supernova,” said Aswin Suresh, a graduate student at Northwestern University.
This excess dust could help explain a long-standing problem in astronomy: the missing red supergiant star.
Astronomers expect the heaviest stars to explode as supernovae to be the brightest and brightest.
Therefore, it should be easy to identify in pre-supernova images. But that wasn’t the case.
One potential explanation is that the most massive, aging stars are the dustiest.
When surrounded by large amounts of dust, the light becomes undetectable.
Webb observations of SN 2025pht support that hypothesis.
“I have argued in favor of that interpretation, but even I never expected it to be as extreme as it was in the case of SN 2025pht,” Dr. Kilpatrick said.
“This could explain why these heavier 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. The results were unexpected because scientists typically expect silicate-rich dust in such environments.
They speculate that this carbon may have been dredged from the star’s interior just before the explosion.
“Observing in the mid-infrared was key to limiting the type of dust we were observing,” Suresh said.
team’s paper In October 2025, Astrophysics Journal Letter.
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Charles D. Kilpatrick others. 2025. Type II SN 2025pht of NGC 1637: A red supergiant star with carbon-rich circumstellar dust, the first JWST detection of a supernova progenitor star. APJL 992, L10; doi: 10.3847/2041-8213/ae04de