JWST spots a hidden giant on the brink of catastrophe
The James Webb Space Telescope (JWST) has provided an unprecedented look at a massive red supergiant just before it exploded as a supernova. The discovery, announced in The Astrophysical Journal Letters, offers a crucial clue to a decades‑old astrophysical puzzle: why some red supergiants disappear from our view long before their fiery end.
The star behind SN 2025pht
The supernova, officially named SN 2025pht, erupted in the spiral galaxy NGC 1637, located about 38 million light‑years from Earth. Using a combination of archival Hubble Space Telescope data and new JWST observations taken before and after the explosion, researchers identified the progenitor star—the red supergiant that ultimately detonated. This is a rare case where astronomers can tie a specific star to a specific supernova, a feat made possible by JWST’s infrared capabilities.
Why this red supergiant looked so unusual
Red supergiants are among the largest and most luminous stars in the universe, often hundreds to thousands of times bigger than our Sun. Yet, the latest JWST data suggest that some of these giants are enshrouded in clouds of dust that conceal their light in visible wavelengths. The team estimates the progenitor shone about 100,000 times brighter than the Sun, but its dusty cocoon dimmed this light by more than a factor of 100 when viewed in optical light. In infrared, where dust absorbs less efficiently, JWST could peer through the veil and reveal the star’s true nature.
Why dust hides red supergiants—and why JWST matters
For decades, astronomers have debated how red supergiants end their lives. If dust shells are common around these stars, many might explode without being properly observed in optical surveys, leading to gaps in our understanding of pre‑supernova behavior. JWST’s infrared sensitivity is a game changer: it allows scientists to study the environments around dying stars as they approach the moment of explosion, offering a more complete picture of the final stages of massive stellar evolution.
Implications for the broader mystery
The new observations support the idea that the most massive aging stars are indeed the dustiest. By directly studying the progenitor of SN 2025pht, researchers can begin to quantify how much dust blocks visible light and how this affects estimates of supernova brightness and frequency. If many red supergiants are hidden behind dusty curtains, the true rate and nature of core‑collapse supernovae may need revision. JWST’s data provide a rare benchmark for calibrating models of stellar death and dust production in galaxies beyond our own.
Looking ahead
As JWST continues to monitor nearby galaxies and archive their pre‑explosion images, the chance of linking other supernovae to their progenitors will grow. Each confirmed progenitor adds a piece to the puzzle of how red supergiants end their lives, how dust forms in stellar environments, and how the brightest stellar explosions illuminate the cosmos for astronomers today and tomorrow.
“SN2025pht is surprising because it appeared much redder than almost any other red supergiant we’ve seen explode as a supernova,” said study lead author Charlie Kilpatrick, a research assistant professor at Northwestern University. “With JWST, we finally have the data quality to identify the exact type of red supergiant that exploded and what its immediate environment looked like.”
