The gamma-ray burst GRB250314A was detected on 14 March 2025 by the Space-based multi-band astronomical Variable Objects Monitor, a French–Chinese telescope launched in 2024. Within 24 hours, NASA’s Neil Gehrels Swift Observatory, the Nordic Optical Telescope in the Canary Islands, and the European Southern Observatory’s Very Large Telescope in Chile were deployed to pinpoint the source. These rapid follow-up observations enabled JWST to begin studying the exceptionally bright flash caused by the explosion of a massive star at the end of its life.
Webb not only observed the earliest supernova ever recorded, but also identified the host galaxy of the exploding star. With this observation, JWST surpassed its own previous record, which involved a supernova dating back to when the universe was 1.8 billion years old.
0,7 billion years old
Andrew Levan, first author of one of the papers, was impressed by JWST’s capabilities: 'With JWST, we were able to immediately demonstrate that this light comes from a supernova—a collapsing massive star. This observation also shows that we can use this space telescope to identify individual stars from a time when the universe was only about 5 per cent of its current age, roughly 0.7 billion years old.'
Although this exceptionally early supernova closely resembles those observed closer to Earth, additional data are needed to uncover any subtle differences. The researchers also hope these observations will shed light on the universe’s first billion years after the Big Bang, a period that remains poorly understood.
JWST was also able to detect light from the supernova’s distant host galaxy. Because the galaxy’s light is concentrated into only a few pixels, it appears as a small red spot in the images. The team has now received approval to use JWST to observe additional afterglows from similar gamma-ray bursts. Levan concludes: 'We hope this will give us a clearer picture of the host galaxies in which these early supernovae occurred.'