A team of astronomers led by Northwestern University has captured the clearest and most detailed view ever of a dying star before its dramatic explosion.
Using NASA’s James Webb Space Telescope (JWST), the international group identified the source of a supernova, known as its progenitor, in mid-infrared light for the first time. When combined with archival observations from the Hubble Space Telescope, the data revealed that the blast originated from a massive red supergiant star wrapped in an unexpected blanket of dust.
This breakthrough may finally explain why astronomers rarely see red supergiants explode, even though models predict they should account for most core-collapse supernovae. The new findings suggest these enormous stars do explode but are often hidden from view by thick dust clouds. Thanks to JWST’s powerful infrared vision, scientists can now see through the obscuring dust, bridging the long-standing gap between theory and observation.
The research, published on Oct. 8 in The Astrophysical Journal Letters, represents JWST’s first confirmed detection of a supernova’s progenitor star.
“For multiple decades, we have been trying to determine exactly what the explosions of red supergiant stars look like,” said Northwestern’s Charlie Kilpatrick, 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, a research assistant professor at Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics, is an expert on the life cycles of massive stars. His coauthor, Aswin Suresh, a graduate student in physics and astronomy at Northwestern’s Weinberg College of Arts and Sciences, played a key role in the analysis.
Reddest, dustiest progenitor ever observed
The team first detected the supernova, named SN2025pht, on June 29, 2025, using the All-Sky Automated Survey of Supernovae. The event’s light traveled from the nearby spiral galaxy NGC 1637, located about 40 million light-years from Earth.
By comparing Hubble and JWST images of NGC 1637 taken before and after the explosion, Kilpatrick, Suresh, and their collaborators pinpointed the progenitor star. It immediately stood out as both brilliant and intensely red. Although the star radiated roughly 100,000 times more light than the Sun, much of its glow was hidden by surrounding dust. The layer of dust was so dense that it made the star appear over 100 times dimmer in visible light than it would otherwise look. Because the dust blocked shorter, bluer wavelengths, the star’s appearance shifted dramatically toward red.
“It’s the reddest, dustiest red supergiant that we’ve seen explode as a supernova,” Suresh said.
Massive stars in the late stages of their lives, red supergiants are among the largest stars in the universe. When their cores collapse, they explode as Type II supernovae, leaving behind either a neutron star or black hole. The most familiar example of a red supergiant is Betelguese, the bright reddish star in the shoulder of the constellation Orion.
“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.”
Clues hidden in dust
The deluge of dust could help explain why astronomers have struggled to find red supergiant progenitors. Most massive stars that explode as supernovae are the brightest and most luminous objects in the sky. So, theoretically, they should be easy to spot before they explode. But that hasn’t been the case.
Astronomers posit that the most massive aging stars also might be the dustiest. These thick cloaks of dust might dim the stars’ light to the point of utter undetectability. The new JWST observations support this hypothesis.
“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.”
In addition to the presence of dust itself, the dust’s composition was also surprising. While red supergiants tend to produce oxygen-rich, silicate dust, this star’s dust appeared rich with carbon. This suggests that powerful convection in the star’s final years may have dredged up carbon from deep inside, enriching its surface and altering the type of dust it produced.
“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.”
A new era for exploding stars
The new study marks the first time astronomers have used JWST to directly identify a supernova progenitor star, opening the door to many more discoveries. By capturing light across the near- and mid-infrared spectrum, JWST can reveal hidden stars and provide missing pieces for how the most massive stars live and die.
The team now is searching for similar red supergiants that may explode as supernovae in the future. Observations by NASA’s upcoming Nancy Grace Roman Space Telescope may help this search. Roman will have the resolution, sensitivity and infrared wavelength coverage to see these stars and potentially witness their variability as they expel out large quantities of dust near the end of their lives.
“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, “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,” was supported by the National Science Foundation (award number AST-2432037).
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