A team led by astronomers from Northwestern University has obtained the most detailed view yet of a star just before it exploded. Using NASA’s James Webb Space Telescope (JWST), the group was able to identify, for the first time, the source star of a supernova at mid-infrared wavelengths. This effort, paired with archival images from the Hubble Space Telescope, revealed that the explosion originated from a massive red supergiant star surrounded by an unexpected amount of dust.
The research addresses a longstanding puzzle in astronomy: theoretical models suggest that most core-collapse supernovae should come from red supergiant stars, but these explosions are rarely observed. The new findings indicate that such events do occur but are often hidden behind thick clouds of dust, making them difficult to detect with traditional telescopes. With JWST’s advanced infrared capabilities, astronomers can now see through this dust and observe these phenomena.
“For multiple decades, we have been trying to determine exactly what the explosions of red supergiant stars look like,” said Charlie Kilpatrick of Northwestern University, who led the study. “Only now, with JWST, do we finally have the quality of data and infrared observations that allow us to say precisely the exact type of red supergiant that exploded and what its immediate environment looked like. We’ve been waiting for this to happen — for a supernova to explode in a galaxy that JWST had already observed. We combined Hubble and JWST data sets to completely characterize this star for the first time.”
Kilpatrick is a research assistant professor at Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics. Aswin Suresh, a graduate student at Northwestern’s Weinberg College of Arts and Sciences and part of Kilpatrick’s group, is also a key coauthor on the paper.
The supernova in question, named SN2025pht, was first detected on June 29, 2025 using the All-Sky Automated Survey of Supernovae. Its light traveled from NGC 1637—a galaxy about 40 million light-years away.
By comparing images taken before and after SN2025pht’s explosion with both Hubble and JWST, researchers identified its progenitor star as extremely bright but heavily obscured by dust. The surrounding dust caused it to appear over 100 times dimmer in visible light than expected without dust interference and gave it an unusually red appearance.
“It’s the reddest, dustiest red supergiant that we’ve seen explode as a supernova,” Suresh said.
Red supergiants like this one are among the universe’s largest stars; when their cores collapse they explode as Type II supernovae—often leaving behind neutron stars or black holes. Betelgeuse is an example of such a star visible from Earth.
“SN2025pht is surprising because it appeared much redder than almost any other red supergiant we’ve seen explode as a supernova,” Kilpatrick added. “That tells us that previous explosions might have been much more luminous than we thought because we didn’t have the same quality of infrared data that JWST can now provide.”
Astronomers have theorized that many massive aging stars might also be those shrouded in thick layers of dust—making them hard or impossible to detect until now. “I’ve been arguing in favor of that interpretation, but even I didn’t expect to see such an extreme example as SN2025pht,” Kilpatrick said. “It would explain why these more massive supergiants are missing because they tend to be dustier.”
The chemical composition of this dust also stood out: instead of being oxygen-rich as expected for such stars, it was carbon-rich—suggesting unusual chemical mixing during its final stages.
“The infrared wavelengths of our observations overlap with an important silicate dust feature that’s characteristic of some red supergiant spectra,” Kilpatrick said. “This tells us that the wind was very rich in carbon and less rich in oxygen, which also was somewhat surprising for a red supergiant of this mass.”
This marks JWST’s first direct identification of a progenitor star for a supernova—opening new possibilities for understanding how massive stars evolve and die through future observations across near- and mid-infrared wavelengths.
With NASA’s Nancy Grace Roman Space Telescope set to launch soon—with improved resolution and sensitivity—the team plans further searches for similar stars on the verge of exploding.
“With the launch of JWST and upcoming Roman launch, this is an exciting time to study massive stars and supernova progenitors,” Kilpatrick said. “The quality of data and new findings we will make will exceed anything observed in the past 30 years.”
The study appears in The Astrophysical Journal Letters and received support from the National Science Foundation.