Astronomers Unravel Mystery Behind Record-Breaking Seven-Hour Gamma-Ray Burst

On July 2, 2025, astronomers detected a remarkable cosmic event known as GRB 250702B, which stands out as the longest gamma-ray burst ever observed. Unlike typical bursts that last mere seconds, this extraordinary event persisted for a full seven hours, emitting three distinct bursts throughout the day. The implications of this discovery have captured the attention of the scientific community, prompting an ongoing investigation into its origins.

Gamma-ray bursts (GRBs) are among the most violent phenomena in the universe, releasing energy that can exceed that of the Sun’s entire ten-billion-year lifespan in just a fraction of a second. Since the recognition of GRBs in 1973, approximately 15,000 bursts have been catalogued, with only a few exhibiting similar durations. Most GRBs arise from catastrophic, one-time events such as neutron star collisions or the collapse of massive stars. GRB 250702B, however, deviates from this norm.

“This is certainly an outburst unlike any other we’ve seen in the past 50 years,” remarked a member of the detection team, underscoring the significance of this anomaly.

Unpacking the Mystery of GRB 250702B

A recently published paper in the Monthly Notices of the Royal Astronomical Society presents a compelling hypothesis regarding the nature of GRB 250702B, suggesting it may be linked to an intermediate mass black hole (IMBH). Black holes exist in various sizes, from stellar mass black holes, formed from dying massive stars, to supermassive black holes found at the centers of galaxies. Intermediate mass black holes, which range from a few hundred to a hundred thousand solar masses, remain elusive, despite theoretical predictions of their abundance.

Researchers propose that GRB 250702B resulted from an ordinary star, similar in size to our Sun, straying too close to an intermediate mass black hole. The immense tidal forces exerted by the black hole could have torn the star apart, creating a relativistic jet of particles that travel close to the speed of light. This jet would have generated the intense gamma-ray emissions detected by the Fermi Gamma-ray Space Telescope.

Notably, the repetitive nature of the bursts aligns with this scenario. The star may not have been entirely destroyed in a single encounter; instead, it could have undergone multiple close passes, each generating a burst of gamma rays. This would explain the timing of the three emissions observed by Fermi.

Significance of the Discovery

The event’s location adds another layer of intrigue. GRB 250702B is situated approximately 5.7 kiloparsecs from the center of its host galaxy, distancing it from the supermassive black hole typically found at galactic cores. This positioning supports the idea that an intermediate mass black hole could exist in that region, potentially confirming a long-sought cosmic mystery.

If the researchers’ hypothesis holds true, GRB 250702B would mark the first observation of a relativistic jet produced by an intermediate mass black hole consuming a star, making it one of the most significant astronomical events in recent years.

Despite the promising theories, the mystery surrounding GRB 250702B is not yet fully resolved. Various competing models remain under consideration, and ongoing research aims to validate the current findings. In an ever-evolving field where groundbreaking discoveries often arise unexpectedly, the occurrence of this seven-hour gamma-ray burst serves as a reminder of the universe’s complexity and the challenges that astronomers face in unraveling its secrets.