NASA's Webb Telescope Finds Record-Breaking Oldest Supernova Ever Recorded

by Aaron Leong — Wednesday, December 10, 2025, 09:20 AM EDT

A faint, ancient flash of light detected by the James Webb Space Telescope (JWST) has broken the record for the most distant stellar explosion ever recorded, revealing a massive star’s demise when the cosmos was just a child. Astronomers confirmed the event occurred approximately 13 billion years ago (versus the Big Bang at 13.8 billion years old).

The discovery originated with a signal known as a long-duration gamma-ray burst (GRB 250314A), first spotted by the Franco-Chinese Space Variable Objects Monitor (SVOM) satellite on March 14. GRBs, the most powerful explosions in the universe, are often the result of a massive star collapsing into a black hole or neutron star.

Subsequent observations by ground-based telescopes, including the European Southern Observatory’s Very Large Telescope in Chile, pinned the event to a redshift of 7.3, confirming its extreme antiquity—just 730 million years after the Big Bang. The previous record-holding supernova (also spotted by JWST) exploded 1.8 billion years after the Big Bang.

supernova artist1 — Artist impression. (Left) Characteristic jets of a gamma-ray burst can be seen punching through material that was ejected by the supernova explosion. (Right) Glowing supernova shines through gas continuing to rush outward from the blast. In the background, the supernova’s host galaxy contains numerous bright star-forming regions.(CreditL NASA, ESA, CSA, STScI, Leah Hustak (STScI))

To confirm the presence of an underlying supernova (or the subsequent brightening after the initial burst of gamma rays), astronomers had to wait. The expansion of the universe creates a phenomenon called cosmic time dilation, which stretches the light and, consequently, the time scale of distant cosmic events. What would typically be a peak brightness lasting a few weeks was stretched, from our perspective, to occur months later. With that in mind, the team, led by Andrew Levan of Radboud University, secured specialized Director’s Discretionary Time on JWST (plus support from an international group telescopes) to observe the location at the precise moment the light was expected to peak on July 1.

"Only Webb could directly show that this light is from a supernova—a collapsing massive star," Levan noted. Utilizing its Near-Infrared Camera (NIRCam), the telescope was able to isolated the faint, stretched light signature of the explosion.

Surprisingly, when the researchers analyzed the light from the record-breaking supernova, they found it to resemble modern supernovae in key ways. Up till now, stars from the early universe were theorized to be fundamentally different. i.e. more massive and containing far fewer heavy elements.

"We went in with open minds," said co-author Nial Tanvir of the University of Leicester. "And lo and behold, Webb showed that this supernova looks exactly like modern supernovae."

This similarity suggests that at least some massive stars during the Epoch of Reionization were much like their younger, modern counterparts. Furthermore, JWST was able to detect the faint, reddened smudge of the host galaxy itself, a tiny structure described as similar to other galaxies seen from that time.