Gamma-ray bursts (GRBs) are the most explosive events in the universe. They release more energy in seconds than our Sun will emit over its entire lifetime. Most GRBs are brief, lasting only fleeting moments. But on July 2, 2025, astronomers detected GRB 250702B, which lasted a remarkable seven hours and emitted multiple bursts throughout the day. This was unlike anything seen before.
Discovered by NASA’s Fermi Gamma-ray Space Telescope, GRB 250702B is now the longest gamma-ray burst known. Among about 15,000 bursts logged since the phenomenon was first identified in 1973, only a few come close in duration. Typically, GRBs are one-time events resulting from spectacular cosmic occurrences like neutron star collisions or the collapse of massive stars. Interestingly, GRB 250702B did not fit that mold. One team member remarked, “This is an outburst unlike any other we’ve seen in the past 50 years,” sparking intense curiosity among scientists.
The intriguing new research published in the *Monthly Notices of the Royal Astronomical Society* suggests that an intermediate mass black hole could be the cause of this prolonged burst. Black holes vary significantly in size. Stellar black holes are a few times heavier than the Sun, while supermassive black holes can weigh millions or even billions of times more. Yet, intermediate mass black holes—ranging from hundreds to thousands of solar masses—are still largely a mystery in astrophysics.
The theory posits that GRB 250702B was triggered when a star similar to our Sun strayed too close to an intermediate mass black hole and was torn to shreds by its powerful gravity. As the star’s material spiraled inward and was consumed, it generated a relativistic jet of particles shooting outward at nearly the speed of light. This would explain the extraordinary gamma-ray emissions detected by Fermi.
What makes this event even more compelling is its repetitive nature. The star might not have been destroyed in one swift moment; instead, it could have been partially stripped during several close approaches to the black hole. Each of these encounters might have led to a new burst of gamma rays, explaining the precise timing of the bursts observed.
Moreover, GRB 250702B is located about 5.7 kiloparsecs from its galaxy’s center, a region where wandering intermediate mass black holes might reside. If this theory holds water, it would mark the first time we’ve observed a relativistic jet created by an intermediate mass black hole devouring a star. This would be a monumental breakthrough in astronomy.
While this theory is exciting, it’s essential to note that other models are still being considered. The competitive nature of astronomical research means that new discoveries often arise unexpectedly. A seven-hour explosion that defies explanation remains a tantalizing puzzle for scientists, pushing the boundaries of our understanding of the universe.
For more information, check out the full study in the *Monthly Notices of the Royal Astronomical Society*: A milli-tidal disruption event model for GRB 250702B: main-sequence star disrupted by an IMBH.
