Astronomers have discovered a bizarre gamma-ray burst labelled GRB 250702B that challenges expectations. Detected by NASA’s Fermi telescope in July 2025, it erupted multiple times over roughly a day; records from China’s Einstein Probe then revealed it had also flared a day earlier. Normally, GRBs are fleeting, one-off blasts from collapsing stars or black-hole disruptions. This newly observed burst defies that, prompting scientists to say it is “unlike any other seen in 50 years of GRB observations”. This unexpected behaviour has surprised astronomers worldwide.
Discovery and Observations
According to the study, Gamma-ray bursts (GRBs) usually signal a single, short-lived explosion from a collapsing star or a star being torn apart by a black hole. GRB 250702B broke the mould. In July 2025, NASA’s Fermi telescope recorded three bursts from this source over a few hours, and Einstein Probe data revealed an outburst the day before. Space.com notes that this GRB “exploded several times in one day”.
ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile pinpointed the source in another galaxy, a result confirmed by Hubble. At a distance of billions of light-years, the burst was extraordinarily powerful.
Possible Causes
Researchers are now scrambling to explain the strange event. Typically, a collapsing star’s explosion emits a brief flash, not a day-long sequence. A star torn apart by a black hole could extend the burst, but the scenario fails to match all observations.
So far no model neatly explains GRB 250702B, suggesting it may represent a new class of these events. Indeed, astronomers stress GRBs “never repeat” in normal circumstances. To resolve the puzzle, the team is using the James Webb Space Telescope and other observatories to search for any afterglow or remnant. Follow-up data may reveal the mechanism behind this unprecedented explosion.
