Kathrine Frich
Astronomers are used to sudden flashes from the distant universe.
Most appear briefly, are catalogued, and then fade into the growing archive of cosmic events.
But every so often, something arrives that refuses to fit existing patterns.
Earlier this year, one such signal prompted an unusual level of global attention.
An extraordinary signal
Scientists revealed that on July 2 they detected an exceptionally long burst of energy coming from deep space.
The event originated around eight billion light years from Earth and immediately stood out for its duration.
Gamma-ray bursts, or GRBs, are among the most powerful explosions known and are usually detected about once a day.
This one, however, continued emitting radiation for more than seven hours, making it the longest GRB ever recorded.
The event was later named GRB 250702B.
Telescopes mobilised
GRB 250702B was first spotted by NASA’s Fermi Gamma-ray Space Telescope, which has been orbiting Earth since 2008.
Once its unusual behaviour became clear, observatories around the world turned their attention to the aftermath.
Major facilities involved included the twin Gemini telescopes in Chile and Hawaii, the Very Large Telescope in Chile, the Keck Observatory in Hawaii and the Hubble Space Telescope.
Astronomers analysed the data to understand what kind of cosmic process could sustain such a prolonged release of energy.
Unclear origins
Researchers now believe the burst came from a rare and previously unseen type of explosion.
Their analysis suggests it launched a narrow jet of material aimed toward the solar system, travelling at least 99% of the speed of light.
Several explanations have been proposed.
These include the collapse of a massive star, a star being torn apart by a black hole, or a scenario in which a black hole spirals into the core of a helium star, triggering an internal explosion.
So far, scientists say they cannot determine which explanation is correct.
A new benchmark
GRBs occur far beyond the Milky Way, with even the closest known examples originating more than 100 million light years from Earth.
In a study published last month in The Astrophysical Journal Letters, researchers said GRB 250702B would become a reference point for future discoveries.
Lead author Jonathan Carney said: “This was the longest gamma-ray burst that humans have observed, long enough that it does not fit into any of our existing models for what causes gamma-ray bursts.”
He added that future explosions would be compared against its unique properties to determine whether they represent the same phenomenon or something entirely new.
