Using the James Webb Space Telescope, astronomers believe they may have witnessed a star die at an almost absurdly early moment in cosmic history. The universe wasn’t even a billion years old yet.
The possible supernova is associated with a powerful gamma-ray burst, GRB 250314A, and appears to have occurred about 730 million years after the Big Bang. If confirmed, it would be the most distant stellar explosion ever observed. Events like this help astronomers trace how the first stars formed, evolved, and ended their lives in a universe that was still young and thinly populated.
GRB 250314A was detected in March by the Space Variable Objects Monitor, an X-ray telescope developed through a China–France collaboration. The burst lasted roughly 10 seconds, long enough to place it in the category typically associated with the collapse of massive stars. Those collapses often end in supernovae, followed by black holes or neutron stars. The problem is that most of these early-universe events vanish before scientists can learn much from them. This one lingered just long enough.
Researchers Say James Webb Might Have Found the Earliest Supernova
Gamma-ray bursts fade quickly, but their afterglows hang around in lower-energy light for days or even weeks. When Webb turned its attention to the site months later, the afterglow should have been nearly gone. Yet there was still light there. That meant astronomers had to play detective and figure out what was actually glowing.
“This leaves us to disentangle the galaxy and the supernova,” said A.J. Levan, lead author of one of two new papers published December 9 in Astronomy & Astrophysics, in an email to Live Science.
One option was strange. The light could’ve come from an unusually compact, very old galaxy with stars forming just 200 million years after the Big Bang. That would be rare, and it would be an odd place to find a gamma-ray burst. The other option made more sense. A supernova.
What surprised researchers next was how familiar that supernova looked. Stars in the early universe were expected to have heavier cores and behave differently from stars today. Instead, this explosion closely resembled modern supernovae.
“We were amazed that our predictions worked so well, and that we had been able to demonstrate that JWST could see individual exploding stars at such extreme distances,” Levan said.
The team plans to follow up with observations after the light fades even more, which should make it easier to separate the supernova’s glow from that of its host galaxy. If this detection holds up, it suggests something quite humbling. The universe learned how to make stars explode pretty early, and it may not have changed that much since.
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