Seven-Hour Gamma-Ray Burst Suggests a New Stellar Merger Engine

Astronomers using the Fermi Gamma-ray Space Telescope detected GRB 250702B, a gamma-ray burst lasting about seven hours—the longest on record—challenging standard GRB models. A helium-merger scenario, where a black hole accretes a helium star and transfers angular momentum to power an unusually long jet, offers a natural explanation. Future work with the COSI gamma-ray telescope, set to launch in 2027, aims to find more long-duration GRBs to unravel the underlying physics.