A brilliant cosmic lightningbrief but immensely powerful, traveled more than 13 billion years before reaching Earthh. She crossed a universe that was still young, turbulent and dark, long before galaxies like ours took shape. The burst was only ten seconds.
Its origin was not immediately clear. But as data accumulated from space and ground telescopes, scientists realized they were observing something far older than anything previously confirmed in its category. A collapsing star, perhaps. Or a type of stellar death not yet fully understood.
Signals like this are not uncommon. They are detected, cataloged and studied. Still, this one stood out. The time it took to arrive and the way it unfolded made it different.
By the time its nature was confirmed, it had broken a record. The light came from a supernova that exploded when the cosmos was only 730 million years old. Not only is it the most distant event of its kind ever observed, but it could also reshape how researchers think about star formation during the first billion years of the universe.
Coordinated international detection
The initial detection took place on March 14, 2025, when the SVOM (Space-based multi-band astronomical Variable Objects Monitor), a joint Franco-Chinese mission, recorded a gamma burst lasting ten seconds. These long bursts are generally associated with the death of massive stars and the birth of black holesemitting focused jets of energy that remain visible over vast cosmic distances.
SVOM’s early successes in identifying what was later designated GRB250314A was remarkable, as the mission had only just begun full operations. Researchers from Paris Observatory – PSL and other European institutions confirmed that the explosion took place during the Reionization epochthe time when the first stars and galaxies began to ionize the intergalactic medium.
A few hours after the detection, NASA Neil Gehrels Swift Observatory located the source of gamma rays. Follow-up observations by the Nordic Optical Telescope And Very Large Telescope (VLT) revealed an infrared afterglow, allowing astronomers to determine a redshift of 7.3indicating that light has traveled over 13 billion years.
Few gamma-ray bursts have been detected at this early stage in cosmic history. According to the Update on ESA’s missionthis particular event now holds the record for the most distant supernova confirmed to date.
Confirmation by the James Webb Space Telescope
Three and a half months after the initial burst, the James Webb Space Telescope (JWST) was directed towards the fading afterglow. This delay was not a setback. Because of the expansion of the universelight from distant objects stretches, a phenomenon known as red shiftand events appear to take place over longer periods of time.
JWST NIRCam And NIRSpec instruments captured images of the supernova and its host galaxyconfirming that the gamma-ray burst came from the collapse of a massive star. This is the first time that a the host galaxy has been detected for a supernova so distant in space and time.
In a peer-reviewed article published in Astronomy and astrophysics letters and cited by the European Southern Observatory And NASAscientists confirmed that GRB 250314A broke the previous distance record set by a supernova observed with a redshift of 4.3.
“Only Webb could directly show that this light comes from a supernova, a massive collapsing star,” said Andrew Levan, a professor at Radboud University and lead author of one of the studies.
The team used a rapidly rotating director’s discretionary time schedule to ensure the event was observed at maximum brightness. The light from the explosion was spread out over time, so capturing the right moment required precise modeling and timing.
Unexpected similarity to modern supernovae
The results challenged long-held assumptions. The explosion did not display the unique chemical or energetic characteristics expected of early universe stars, often called Population III stars. These first generation stars, devoid of heavy elements (or metals), would have died in asymmetric and highly energetic explosions.
Instead, the data from JWST observations revealed a standard Type II supernovaclosely matching those observed in the local universe today. This suggests that the processes that determine star death, and perhaps even chemical enrichment, were already well underway just 730 million years after the Big Bang.
Nial Tanvir, professor at the University of Leicester and co-author of the study, noted: “Webb showed that this supernova looks exactly like modern supernovae. »
If confirmed in additional events, it could indicate that galaxies evolved faster than previously thought, producing several generations of stars in a relatively short cosmological time frame.
Implications for early cosmic evolution
The detection of GRB 250314A provides new insight into how quickly complexity arose in the early universe. Thanks to the combined efforts of SVOM, JWSTand other ground installations, researchers were able to confirm both the nature of the explosion and the structure of its host environment.
The discovery also illustrates how gamma-ray bursts can serve as powerful tools for probing the earliest epochs of the universe. Their brightness and distinct signatures allow scientists to trace cosmic events that occurred billions of years ago, providing a complementary approach to traditional deep-field imaging.
Researchers involved in the current project have obtained additional observation time on JWST to monitor similar high-redshift events. These future campaigns will focus on detecting afterglow And host galaxieshelping astronomers to get a clearer idea of early stellar evolution.
