JWST identifies SN Eos: The most distant supernova ever spectroscopically confirmed
Astronomers using NASA’s James Webb Space Telescope identified a supernova, SN Eos, that exploded when the universe was 1 billion years old, marking the most distant stellar explosion confirmed via spectroscopy.
SN Eos, detected at a redshift of 5.133 by the JWST’s Vast Exploration for Nascent, Unexplored Sources (VENUS) collaboration, provides insight into massive star deaths in the early cosmos. David Coulter of Johns Hopkins University led the research team, which first identified the transient in JWST imaging of the MACS 1931.8-2635 galaxy cluster field on September 1, 2025. Findings were published on the arXiv preprint server on January 7.
The supernova, which exploded shortly after the epoch of reionization, became visible due to gravitational lensing from a foreground galaxy cluster that amplified its light 25 to 30 times, producing multiple images.
Follow-up JWST spectroscopy on October 8, 2025, confirmed SN Eos as a Type II supernova, displaying hydrogen-rich signatures, including Balmer P-Cygni profiles. The team classified it as a Type IIP supernova at the end of its plateau phase, a period of sustained luminosity from hydrogen recombination.
Spectral data indicated SN Eos’s progenitor star formed in an environment with metal concentrations less than 10% of the Sun’s abundance, evidenced by weak iron absorption lines. This provides direct evidence of massive star formation and death in the metal-poor early universe. Or Graur from the University of Portsmouth said this immediately informs about the stellar population from which the star exploded, noting high-mass stars explode quickly after formation, tracing ongoing star formation.
SN Eos’s host galaxy is an ultra-faint Lyman-alpha emitting galaxy that would have been undetectable without the supernova acting as a beacon. Archival Hubble Space Telescope imaging from March 2024 captured rest-frame far-ultraviolet emission days after the explosion, showing evidence of shock breakout or interaction with circumstellar material. Matt Nicholl of Queen’s University Belfast said, “We can observe this singular star with remarkable data at a distance where isolated supernovae have never been seen, and the quality of the data is sufficient to demonstrate that these stars differ from most found in the local universe.”
This discovery represents a critical step toward JWST’s mission of understanding the lives and deaths of the universe’s first stars and their role in seeding the cosmos with chemical elements.