Ten seconds. That is how long an intense burst of high-energy light lit up space in March 2025, after traveling for about 13 billion years before reaching Earth. For astronomers, those few seconds opened a window onto a time when the universe was still in its cosmic childhood, only about 730 million years old.
An international team has now confirmed that this flash, labeled GRB 250314A, came from the death of a massive star in one of the earliest known galaxies. Using the James Webb Space Telescope together with a new French-Chinese satellite and several ground-based observatories, they have identified the earliest supernova ever seen and found that it looks far more familiar than many experts expected, as described in a detailed NASA overview. What can ten seconds of light really tell us about the birth of stars and galaxies?
A Ten-Second Flash From the Cosmic Dawn
The story began on March 14, 2025, when the SVOM satellite spotted a sudden spike of gamma rays, the most energetic type of light. These brief events, called gamma-ray bursts, are among the most powerful explosions in the cosmos and often mark the final collapse of a very massive star.
SVOM, a space telescope designed by France and China to catch such fleeting signals, immediately broadcast an automated alert to astronomers around the world. Within about ninety minutes, NASA’s Neil Gehrels Swift Observatory had pinned down the position of the burst in the sky, and other telescopes began to swing toward the new target.
Hours later, the Nordic Optical Telescope in the Canary Islands and the Very Large Telescope in Chile picked up the fading glow of the burst in infrared light. By splitting that light into its colors, astronomers measured how strongly it had been stretched by the expansion of the universe, concluding that the explosion happened when the cosmos was only a few hundred million years old.
From Gamma-Ray Burst to Earliest Known Supernova
A gamma-ray burst is only the opening act in the death of a star. The initial flash may last from a fraction of a second to a few minutes, but the wrecked star then continues to brighten as a supernova, which normally reaches peak brightness over several weeks before slowly fading.
Because this event took place so early in cosmic history, its light has been stretched in both color and time as it crossed expanding space. What would have unfolded over weeks in a nearby galaxy played out over several months in our telescopes, giving observers a rare chance to plan detailed follow-up.
On July 1, about three and a half months after the burst, the James Webb Space Telescope used its near-infrared camera to take sharp images of the region. In those pictures, researchers could separate the glow of the supernova from the faint smudge of its host galaxy, confirming that a single massive star had collapsed and blown apart in the young universe.
An Ancient Explosion That Looks Surprisingly Modern
Many theories have predicted that the very first generations of stars were heavier, shorter-lived, and more extreme than the stars we see today. If that were true, their final explosions might have left very unusual signatures, perhaps brighter or with different patterns of chemical elements.
Instead, the team, led by Andrew Levan of Radboud University, found that the properties of this supernova looked strikingly similar to those of more recent stellar explosions in our cosmic neighborhood. Its brightness over time and the features in its light suggested that the same basic physics was already at work less than a billion years after the Big Bang.
What GRB 250314A Tells Us About the First Stars
In a companion press release from the Paris Observatory, Bernard Cordier and colleagues using SVOM and large ground-based telescopes showed that GRB 250314A erupted during a period called the era of reionization, when the first generations of stars and galaxies slowly cleared away a fog of hydrogen gas that filled space after the Big Bang. Their work, supported by scientists at the Paris Observatory, also confirms that this gamma-ray burst is among the most distant ever precisely measured and that its associated blast is the oldest supernova ever directly detected.
Events like this do not change anyone’s electric bill or daily commute, but they do reshape our picture of how everything in our world first came to be. The elements in our blood, our phones, and our cities were forged in ancient stars, and explosions like GRB 250314A helped spread those elements through space so that later generations of stars and planets could form.
The main study has been published in Astronomy & Astrophysics.