Astronomers utilizing the NASA/ESA/CSA James Webb Space Telescope have made a groundbreaking discovery: they have identified a nearby supernova, specifically a red supergiant star, that was obscured by a thick layer of dust and remained invisible to prior observatories.

This striking image combines observations from both the James Webb Space Telescope and Hubble, focusing on spiral galaxy NGC 1637. It captures the evolutionary stages of the red supergiant star and reveals its transformation following the supernova event SN 2025pht. Image credit: NASA/ESA/CSA/STScI/C. Kilpatrick, Northwestern/A. Suresh, Northwestern/J. DePasquale, STScI.

The supernova event, designated SN 2025pht, was first identified in NGC 1637 on June 29, 2025.

In response, astronomers dedicated substantial resources to investigating this supernova.

However, Northwestern University’s astronomer Charlie Kilpatrick and his team chose to explore archival data, analyzing pre-supernova images to determine which star exploded.

A 2024 image of NGC 1637 captured with Webb’s MIRI (Mid-Infrared Instrument) and NIRCam (Near-Infrared Camera) highlights a distinct red supergiant star positioned precisely where SN 2025pht is currently visible.

“We anticipated this moment, hoping for a supernova to occur in a galaxy that Webb was already monitoring,” stated Dr. Kilpatrick.

“By integrating the Hubble and Webb datasets, we unveiled the star’s complete characteristics for the first time.”

“This red supergiant represents the dustiest star we have ever observed transitioning into a supernova,” noted Aswin Suresh, a graduate student at Northwestern University.

This dust anomaly may help solve a persistent mystery in astronomy: the absence of certain red supergiant stars.

Astronomers expect that the most massive stars should explode as the brightest supernovae, making their identification in pre-explosion images straightforward. However, this has not been the case.

One possible explanation is that these massive, aging stars are often heavily surrounded by dust, rendering their light invisible.

Observations from Webb regarding SN 2025pht seem to support this hypothesis.

“I have advocated for this interpretation, but I didn’t expect the outcome to be as pronounced as in the case of SN 2025pht,” commented Dr. Kilpatrick.

“This might clarify the absence of these heavier supergiant stars, as they tend to be engulfed in more dust.”

The team also discovered that the dust enveloping the star is likely rich in carbon—an unexpected finding, as silicate-rich dust is typically anticipated in these environments.

They speculate that this carbon may have been released from the star’s core shortly before the explosion.

“Mid-infrared observations were crucial in identifying the specific type of dust present,” Suresh added.

For more in-depth details on this discovery, view the team’s research paper published in October 2025 in the Astrophysics Journal Letter.

_____

Charles D. Kilpatrick et al. 2025. Type II SN 2025pht of NGC 1637: Detection of a red supergiant star with carbon-rich circumstellar dust, marking the first acknowledgment of a supernova progenitor star via JWST. APJL 992, L10; doi: 10.3847/2041-8213/ae04de