Astronomers Witness Longest-Lasting Gamma-Ray Burst in History, 8 Billion Light-Years Away

Astronomers have spotted an extraordinarily long-lived cosmic explosion lasting more than seven hours, breaking the record as the longest known gamma-ray burst. The event, known as GRB 250702B, took place 8 billion light-years away from the solar system and produced an enormous amount of energy – so much that it stands out as unlike anything else NASA's Fermi Gamma-ray Space Telescope has recorded before. Scientists quickly enlisted a raft of world-class observatories to follow up on this afterglow and study its host galaxy — one that is highly obscured by dust and opaque at optical wavelengths, but transparent in X-rays as well as in the infrared range used by Gemini telescopes, the Very Large Telescope, Keck Observatory, and Hubble Space Telescope.

Unprecedented Seven-Hour Gamma-Ray Burst Challenges Existing Astrophysics Models

According to a report published in The Astrophysical Journal Letters on November 26, 2025, Jonathan Carney, lead author and a doctoral student at the University of North Carolina, mentioned that GRB long duration is uncommon for existing gamma-ray burst models. The event could have been caused by the collapse of a large star, a black hole devouring a star and ejecting matter at close to light speed, or the merger of an ultra-dense object and a massive velocity jet blasting directly towards Earth.

The find is a testament to global telescope coordination; GRB 250702B's long duration and remote location add precision to models of stellar death, black holes, and the physics of jets.

Seven-Hour GRB Suggests a New Class of Ultra-Long Cosmic Explosions

Researchers witnessed a seven-hour GRB, which would imply a new class of ultra-long GRBs; whether such processes apply or there is some new physics retained will be determined by future detections.

Such discoveries help to shed light on high-energy phenomena occurring across the universe, providing insights into the life cycle of massive stars and the formation of exotic objects such as black holes.