GRB 250702B Sets Record as Longest Gamma-Ray Burst Observed

GRB 250702B has drawn attention in the scientific community due to its exceptional duration and complex emission pattern, offering new insights into gamma-ray burst phenomena.

On July 2, 2025, NASA’s Fermi Gamma-ray Space Telescope detected a gamma-ray burst designated GRB 250702B, which persisted for approximately seven hours. This event stands out as the longest gamma-ray burst recorded to date, surpassing previous observations in both length and structure.

Analysis of the event showed that GRB 250702B consisted of several gamma-ray emission episodes originating from the same region in the sky over several hours. Prior to the gamma-ray activity, China’s Einstein Probe registered soft X-ray emissions from the same location about a day earlier, indicating a precursor phase to the main burst.

High-resolution imaging from the Hubble Space Telescope and the James Webb Space Telescope placed the burst near the periphery of its host galaxy, approximately 1,900 light-years from the galactic center. This spatial information has contributed to ongoing discussions about the possible origins of such long-duration gamma-ray bursts.

What the numbers show

• The burst lasted about 25,000 seconds, or roughly seven hours
• Previous gamma-ray burst records were around 15,000 seconds
• The burst’s location is approximately 1,900 light-years from its galaxy’s center

Several theoretical models have been advanced to account for the unusual properties of GRB 250702B. One explanation involves a helium merger scenario, where a black hole merges with a helium star and generates a sustained jet. This model is consistent with the extended emission observed during the event.

Alternative theories include a relativistic tidal disruption event, in which a star is torn apart by a black hole, producing a jet that emits gamma rays. Another proposed mechanism is a micro-tidal disruption event, where a compact object disrupts a star, potentially explaining both the early X-ray signal and the prolonged gamma-ray activity.

Additional models suggest that a precessing magnetic jet, resulting from a misaligned debris disk around a black hole, could cause episodic gamma-ray pulses through a process known as Lense-Thirring precession. There is also a milli-tidal disruption event hypothesis, involving an intermediate-mass black hole disrupting a main-sequence star, which may account for the observed afterglow and energy output.

Researchers continue to analyze data from GRB 250702B to refine these models and improve understanding of the processes behind ultra-long gamma-ray bursts. The event’s unique characteristics have provided new data for evaluating existing theories and developing new approaches to gamma-ray burst research.

* This article is based on publicly available information at the time of writing.