NASA’s James Webb Space Telescope has uncovered evidence of a stellar explosion that could help solve a cosmic mystery millions of years in the making: what NASA calls the “case of missing red supergiants.”
This odd celestial story begins forty million years ago, following the explosion of a star in a galaxy close to ours. In the aftermath of this stellar destruction, star stuff was ejected across space, leaving a trail of clues to what occurred there eons ago.
Fast forward to June 2025, when light from that cataclysmic event finally reached Earth and was detected by the All-Sky Automated Survey for Supernovae, which attracted significant attention from astronomers. The supernova, dubbed 2025 pht, prompted studies that included searches of stellar archives, which researchers hoped would help narrow down which star had been the casualty in this cosmic cold case.
Soon, their work paid off, although unlike Sherlock Holmes, astronomers needed something larger than a magnifying glass to solve this mystery.
Enter NASA’s James Webb Space Telescope, whose powerful eye successfully captured images of a single red supergiant star, which, based on comparisons with existing stellar imagery, is a perfect match for the new location of the brilliant supernova that now shines like a beacon from across the cosmos.
Significantly, the researchers behind the study say this marks the Webb Telescope’s first confirmed detection of a supernova progenitor, revealed in its imagery of the galaxy NGC 1637.
A Star’s Explosion Captures Attention
“We’ve been waiting for this to happen,” said Charlie Kilpatrick, an astronomer at Northwestern University and the lead author of a new study that appeared in The Astrophysical Journal Letters.
According to Kilpatrick, he and his colleagues had been hoping for “a supernova to explode in a galaxy that Webb had already observed.” Such a rare opportunity allowed the researchers to compare Webb’s imagery with earlier views from its predecessor, the Hubble Space Telescope, enabling them to “completely characterize this star for the first time.”
At the heart of the team’s work, alignments between earlier Hubble images and the newer cosmic vistas obtained by Webb centered on the galaxy NGC 1637, revealing the unequivocal presence of the supernova’s progenitor star. Webb’s powerful MIRI (Mid-Infrared Instrument) served as the key technology behind these detections, along with its NIRCam (Near-Infrared Camera), which both acquired images of the star in question in 2024.
At these wavelengths, Webb’s cameras provided a view unlike anything seen in the Hubble imagery—specifically, a “surprisingly red” star emerged, revealing that the cosmic material surrounding it had likely impeded the passage of blue wavelengths of light.
Aswin Suresh, who is a co-author of the paper and a graduate student currently at Northwestern University, called it “the reddest, most dusty red supergiant that we’ve seen explode as a supernova.”
A Dusty Clue to a Cosmic Mystery
The large amount of dust surrounding the star in question is an important discovery, as it may offer astronomers a clue toward solving a longstanding mystery: the case of the missing red supergiants.
A longstanding issue in astronomy, researchers anticipate that for stars to become so massive that they explode as supernovae, they should also be among the brightest objects that are visible to us.
Much to astronomers’ surprise, the opposite appears to be the case: some of the most massive, ancient stars that should be candidates are surprisingly difficult to spot in pre-supernova images. One possible reason is that such large stellar bodies may be surrounded by significant amounts of dust, which can greatly reduce the amount of their light visible from Earth.
In some cases, such stars might be encased in so much dust that they become virtually invisible to astronomers, and based on the newest Webb data, supernova 2025pht seems to help clinch this theory.
Solving the Mystery of the Missing Red Supergiants
Kilpatrick said that even though he supported this idea, he never expected that there would be so much dust accumulating around a supernova progenitor.
“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,” Kilpatrick said in a statement, adding that the new observations “would explain why these more massive supergiants are missing because they tend to be more dusty.”
An additional surprise came in the form of the composition of the dust surrounding the star in question. Based on computer models the team used with Webb Telescope data, the dust is most likely very rich in carbon, rather than containing large amounts of silicate, as had been expected based on past theories. This excessive amount of carbon could be linked to emissions from the star’s interior that occurred just prior to the explosion occurring.
Going forward, the team says it plans to search for additional red supergiants to help broaden their understanding of the phenomena involving these previously “missing” stellar monsters. Future observations with NASA’s upcoming Nancy Grace Roman Space Telescope are expected to provide even more data about these unique stars and the conditions that lead to the carbon accumulation around them prior to the occurrence of supernovas.
The team emphasized that the discoveries could not have been made without Webb’s help.
“Having observations in the mid-infrared was key to constraining what kind of dust we were seeing,” Suresh said in a statement.
The team’s research was featured in a new paper, “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,” published in the Astrophysical Journal Letters.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.