Webb Telescope Reveals Hidden Red Supergiant Before Supernova Explosion
In a groundbreaking discovery, the James Webb Space Telescope (JWST) has captured the clearest and most detailed view yet of a dying star before its dramatic explosion as a supernova. This observation, combined with archival data from the Hubble Space Telescope, has revealed a massive red supergiant star shrouded in an unexpected blanket of dust, finally offering a potential explanation for the mystery of missing red supergiants.
Unveiling the Progenitor Star
Astronomers first detected the supernova, designated SN2025pht, on June 29, 2025, using the All-Sky Automated Survey for Supernovae. A team led by Northwestern University then turned to images of the host galaxy, NGC 1637, taken by JWST prior to the explosion. The team successfully identified the progenitor star – the star that exploded – within the galaxy.
“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.
Dusty Origins and the Missing Red Supergiant Problem
The JWST observations, particularly those from the Mid-Infrared Instrument (MIRI) and Near-Infrared Camera (NIRCam), revealed that the red supergiant was surprisingly red. This indicates the presence of significant amounts of dust blocking 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 discovery addresses a long-standing puzzle in astronomy: the scarcity of observed red supergiants exploding as supernovae. Theoretical models predict that massive stars should frequently end their lives as bright, easily detectable supernovae, but observations haven’t matched those predictions. The excessive dust surrounding SN2025pht’s progenitor star suggests that many massive stars may be hidden from view by similar dust clouds.
“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.
Unexpected Dust Composition
Further analysis of the dust surrounding the star revealed an unexpected composition. Computer models based on the JWST observations suggest the dust is likely carbon-rich, rather than the silicate-rich composition astronomers typically expect in these environments. Researchers speculate that this carbon may have been brought to the surface from the star’s interior shortly before the explosion.
“Having observations in the mid-infrared was key to constraining what kind of dust we were seeing,” said Suresh.
Future Observations and the Roman Space Telescope
The team plans to continue searching for similar red supergiants that may explode as supernovae. Future observations from NASA’s Nancy Grace Roman Space Telescope, with its enhanced resolution, sensitivity and infrared capabilities, will be instrumental in this search. The Roman Space Telescope may even be able to observe the variability of these stars as they release large quantities of dust near the end of their lives.
About the James Webb Space Telescope
The James Webb Space Telescope is an international program led by NASA in partnership with the European Space Agency (ESA) and the Canadian Space Agency (CSA). It is designed to solve mysteries in our solar system, study distant worlds around other stars, and explore the origins of the universe.
Learn more about the James Webb Space Telescope: https://www.jwst.nasa.gov/
About NGC 1637
NGC 1637 is an isolated, non-interacting intermediate spiral galaxy located in the constellation Eridanus, approximately 40 million light-years from Earth. It was discovered by William Herschel on February 1, 1786. The galaxy has coordinates of 04h 41m 28.229s, −02° 51′ 28.94″.