NASA’s James Webb Space Telescope has observed a supernova that exploded when the universe was only 730 million years old — the earliest detection of its kind to date. Webb’s crisp near-infrared images also allowed astronomers to locate the supernova’s faint host galaxy. The telescope took these quick-turn observations July 1 in support of an international group of telescopes that detected a super bright flash of light known as a gamma-ray burst in mid-March. NASA’s missions are part of a growing, worldwide network watching for fleeting changes in the skies to solve mysteries of how the universe works.
NASA’s James Webb Space Telescope identified the source of a super bright flash of light known as a gamma-ray burst: a supernova that exploded when the universe was only 730 million years old. Webb’s high-resolution near-infrared images also detected the supernova’s host galaxy.Image: NASA, ESA, CSA, STScI, Andrew Levan (Radboud University); Image Processing: Alyssa Pagan (STScI)
With this observation, Webb also broke its own record: The previous chart-topping supernova exploded when the universe was 1.8 billion years old.
“Only Webb could directly show that this light is from a supernova — a collapsing massive star,” said Andrew Levan, the lead author of one of two new papers in Astronomy and Astrophysics Letters and a professor at Radboud University in Nijmegen, Netherlands, and the University of Warwick in the United Kingdom. “This observation also demonstrates that we can use Webb to find individual stars when the universe was only 5% of its current age.”
While a gamma-ray burst typically lasts for seconds to minutes, a supernova rapidly brightens over several weeks before it slowly dims. In contrast, this supernova brightened over months. Since it exploded so early in the history of the universe, its light was stretched as the cosmos expanded over billions of years. As light is stretched, so is the time it takes for events to unfold. Webb’s observations were intentionally taken three and a half months after the gamma-ray burst ended, since the underlying supernova was expected to be brightest at that time.
“Webb provided the rapid and sensitive follow-up we needed,” said Benjamin Schneider, a co-author and a postdoctoral researcher at the Laboratoire d’Astrophysique de Marseille in France.
Gamma-ray bursts are incredibly rare. Those that last a few seconds may be caused by two neutron stars, or a neutron star and a black hole colliding. Longer bursts like this one, which lasted around 10 seconds, are frequently linked to the explosive deaths of massive stars.
The first alert chimed March 14. The news of the gamma-ray burst from a very distant source came from the SVOM mission (Space-based multi-band astronomical Variable Objects Monitor), a Franco-Chinese telescope that launched in 2024 and was designed to detect fleeting events.
Within an hour and a half, NASA’s Neil Gehrels Swift Observatory pinpointed the X-ray source’s location on the sky. That enabled subsequent observations that would pin down the distance for Webb.
Eleven hours later, the Nordic Optical Telescope on the Canary Islands was queued up and revealed an infrared-light gamma-ray burst afterglow, an indication that the gamma ray might be associated with a very distant object.
Four hours later, the European Southern Observatory’s Very Large Telescope in Chile estimated the object existed 730 million years after the big bang.
“There are …