Astronomers Identify First Red Giant Supernova Candidate Using ASAS-SN and JWST

Researchers at Northwestern University have announced a significant astronomical breakthrough: the identification of the first red giant star that is definitively predicted to end its life in a powerful supernova explosion. This landmark achievement, detailed in the October 8, 2025, edition of Astrophysical Letters, offers crucial insight into a long-standing cosmic mystery regarding stellar demise. The star, designated SN2025pht, resides in the NGC 1637 galaxy, situated approximately 39 million light-years from Earth. Current projections suggest that SN2025pht will detonate as a supernova within the next few million years, ultimately collapsing into either a pulsar or a black hole.

The ability to pinpoint this precursor was the result of meticulous data analysis conducted by Charles Kilpatrick and Aswin Suresh. They utilized the All-Sky Automated Survey for Supernovae (ASAS-SN), a system that continuously monitors the night sky for sudden shifts in stellar luminosity—often harbingers of an impending stellar catastrophe. The team cross-referenced this information with archival data from the Hubble Space Telescope to precisely characterize the star's location and nature, confirming its status as a red giant supernova candidate. Theoretical models have long posited that red supergiants should account for the majority of observed supernovae, yet direct observation of such a precursor object has remained elusive until now.

This discrepancy, often termed the “red supergiant problem,” is believed to stem from observational limitations. During the transition phase leading up to a supernova, the star can generate copious amounts of dust, effectively obscuring its visible light and shifting its spectral signature into the infrared range. In the specific case of SN2025pht, this dust, composed primarily of carbon, is being expelled by slow but forceful stellar winds. Following the initial detection by ASAS-SN, the James Webb Space Telescope (JWST) performed targeted observations of SN2025pht, revealing intense infrared emission.

Dr. Kilpatrick proposed that previous estimates regarding the size and frequency of supernova progenitors might have been underestimated because Hubble lacked the necessary infrared capability to fully characterize these dusty, “reddened” objects. JWST's unique capacity to analyze dust clouds and infrared bodies holds the potential to revolutionize the classification of previously recorded dying stars. Dr. Kilpatrick expressed confidence that as the JWST archives grow, the detection of these rare red giant supernova precursors will become increasingly common.

However, he cautioned that capturing such stars currently requires them to be relatively close for initial observation by Hubble, meaning it will still take several years for JWST to amass a substantial dataset. This finding echoes earlier observations, such as Supernova 2003gd in the M74 galaxy, where Hubble and the Gemini telescope documented a red supergiant 6–9 months before its explosion, confirming the theory that cool red supergiants are the direct precursors to Type II-plateau supernovae. Crucially, the application of infrared data, as demonstrated with SN2025pht, may finally help resolve the long-standing issue associated with the mismatch between the observed mass and the theoretically expected mass of supernova progenitors, closing a significant gap in our understanding of stellar evolution and death.