Astronomers Observe Unprecedented Seven-Hour Gamma-Ray Burst

On July 2, 2025, NASA's Fermi Gamma-ray Space Telescope detected an extraordinary gamma-ray burst (GRB) that persisted for over seven hours, significantly longer than typical GRBs, which usually last from milliseconds to minutes. This event, named GRB 250702B, originated from a galaxy approximately 8 billion light-years away in the constellation Scutum.

Astronomers worldwide mobilized to study the phenomenon, utilizing instruments such as the Very Large Telescope in Chile, the Keck Observatory in Hawaii, and the Hubble Space Telescope. These observations revealed that the host galaxy's dense dust obscured visible light, allowing only infrared and high-energy X-ray wavelengths to be detected.

Jonathan Carney, lead author of a study published in The Astrophysical Journal Letters, stated, "This was the longest gamma-ray burst that humans have observed — long enough that it does not fit into any of our existing models for what causes gamma-ray bursts."

Researchers are considering several explanations for GRB 250702B, including the collapse of a massive star, a star being torn apart by a black hole, or the merger of a helium star and a black hole. However, no definitive cause has been identified. Carney noted, "But we can't yet tell which explanation is correct. In the future, this event will serve as a unique benchmark — when astronomers discover similar explosions, they'll ask whether they match GRB 250702B's properties or represent something different entirely."

The unprecedented duration and characteristics of GRB 250702B challenge existing astrophysical models and may indicate a previously unobserved type of cosmic explosion. Ongoing studies aim to uncover the mechanisms behind this remarkable event.