A 7-hour long gamma-ray burst (GRB) – the most energetic type of explosion in the Universe since the Big Bang – was detected on July 2, 2025 by NASA’s Fermi Gamma-ray Space Telescope, which has been orbiting Earth since 2008.
The event, called GRB 2507028, is the longest gamma-ray burst ever recorded. Astronomers now believe its origins are linked to another previously unseen explosion, which launched a narrow jet of cosmic radiation toward the Solar System, traveling at at least 99 percent of the speed of light.
GRB 2507028 was not easy to identify. Researchers used several types of telescopes to pinpoint its origin, across all wavelengths of light, including the twin 8.1-meter Gemini telescopes in Chile and Hawaii, the Very Large Telescope in Chile, the Keck Observatory in Hawaii, and the Hubble Space Telescope.
Gamma ray bursts come from the depths of the Universe. Even the closest such event came from more than 100 million light-years away, according to NASA.
According to astronomers, GRB 2507028 originated from a massive galaxy 8 billion light-years away, which is so rich in cosmic dust that it blocked out almost all visible light.
The only light detected by the telescopes was infrared and high-energy X-rays. Because of the dense dust clouds in the home galaxy, the GRB phenomenon was almost invisible in the visible light spectrum, according to the study.
“This was the longest gamma-ray burst ever observed, long enough to not fit into any of our existing models of what causes gamma-ray bursts,” Jonathan Carney, the study’s lead author and a doctoral candidate in physics and astronomy at the University of North Carolina at Chapel Hill, said in a statement.
The analysis shows that GRB 2507028 could have been caused by the death of a massive star, a star torn apart by a black hole, or the merger of a helium star and a black hole, in which the black hole pierces the core of the massive star, triggering an explosion from within. The study states that, for now, there is not enough data to tip the balance towards one of these causes.
