Webb Telescope Captures Ghostly Light from a 13-Billion-Year-Old Supernova

A flash of light from a dying star, traveling for 13 billion years, has finally reached us. In an observation that pushes the boundaries of what’s possible, the James Webb Space Telescope has captured the direct aftermath of a supernova that exploded when the universe was just a toddler, a mere 730 million years after the Big Bang. The event, triggered by a powerful gamma-ray burst, marks the violent end of a massive star and potentially the birth of a black hole in the cosmic dawn, giving astronomers a direct look at an era previously shrouded in theory.

“Only a handful of gamma-ray bursts over the last 50 years have been detected from the universe’s first billion years. This event is exceptionally rare and incredibly exciting,” stated Andrew Levan of Radboud University in the Netherlands and the University of Warwick in the UK.

The cosmic detective story began on March 14, when the Franco-Chinese SVOM satellite picked up a fleeting burst of gamma rays from deep space. The alert sent observatories scrambling. Ninety minutes later, NASA’s Swift observatory locked onto the same event, cataloged as GRB 250314A, in X-rays, giving astronomers a precise location on the sky. The chase continued on the ground, with the Nordic Optical Telescope in the Canary Islands spotting the faint, fading afterglow 11 hours later. A few hours after that, Chile’s Very Large Telescope measured the light’s redshift at a staggering 7.3, confirming its immense distance and 13-billion-year-old origin.

But observing the supernova itself, not just its initial flash, presented a unique challenge. The universe’s expansion stretches not only light but also time from our perspective. An explosion that would normally peak in brightness over days or weeks would appear to us to take three and a half months. Seizing this slow-motion window, Levan’s team successfully argued for director’s discretionary time on the James Webb Space Telescope. On July 1, Webb’s powerful Near-Infrared Camera pointed at the coordinates and saw it: the unmistakable, fading light of the supernova itself. “Only Webb could directly show that this light came from a supernova—from the collapse of a massive star,” Levan explained. “This observation also proves we can use Webb to spot individual stars in an era when the universe was just 5% of its current age.”

Left: An artist’s illustration of the gamma-ray burst. Right: The ancient supernova that caused it. Image credit: ESA

Webb’s sharp vision also managed to resolve the supernova’s home, a galaxy that appears as little more than a blurry smudge of pixels. Even from this faint image, scientists can extract clues about the environment where the star died. But does this ancient explosion truly rewrite our understanding of the early universe, or simply confirm what theories have long predicted? According to Emeric Le Floc’h of CEA Paris-Saclay, a member of the team publishing the findings in the journal Astronomy and Astrophysics, “The observations show that this distant galaxy looks like others that existed at the same time.”

The supernova’s light signature, or spectrum, also holds a surprising revelation: it looks remarkably similar to explosions seen in the modern universe, suggesting the star that died wasn’t unusually massive by today’s standards. This finding is somewhat counterintuitive, as stars in the early universe were forged from a much simpler chemical recipe, lacking the heavy elements common today. Subtle but significant differences are expected to be hiding in the data. To truly unpack these details, continued investment in multi-instrument, rapid-response astronomy is essential. More analysis is required to see if this ancient star’s death was truly a carbon copy of modern ones, or if it holds secrets unique to its primordial era.

For now, the discovery sets a new, definitive record. It is the most distant supernova ever spectroscopically confirmed, shattering the previous record—also set by Webb—of a supernova from 1.8 billion years after the Big Bang. This observation is more than just a new entry in the record books; it’s a precious, direct data point from a time when the first stars were lighting up the cosmos, offering a tangible connection to the universe’s very beginning.