Astronomers have spotted the highest-energy radiation ever seen from the most powerful and luminous cosmic explosion in the universe. The blast of radiation, known as gammarays, came in two bursts that hit Earth with more than 100 billion times the energy in visible light.
Gamma-ray bursts, or GRB, are the most intensely energetic phenomenon in the universe, suddenly appearing in the sky for only a brief period but releasing the same amount of energy in one second that the Sun will emit in its entire life. GRBs are thought to come out of massive stars when they collapse at the end of their lives, or when binary star systems merge into much smaller objects. As they do, they throw out a flash of radiation that flies across the whole universe.
When observed, they begin with a bright flash that is then followed by an “afterglow”. That afterglow throws out emissions across a range of different energies, including the very intense gigaelectronvolt gammarays – of which few have ever been seen. Gamma-ray bursts were first spotted during the Cold War. During that period, the US and former Soviety Union had satellites in orbit looking for gamma-rays being thrown out by the explosion of an atomic bomb.
Every so often, they would send an alert that they had spotted a huge increase in those gamma-rays. But there was no evidence of a nuclear explosion.
Gamma-ray bursts have stayed mysterious, in part because the data was kept strictly classified and in part because they are so difficult to track down.
Now scientists hope to delve into that mystery after spotting the newly energetic blast. Specialised telescopes were able to see the blast of photons, which reached about 100 billion times the level of visible light.
The breakthrough began when Nasa satellites spotted what appeared to be a gamma-ray burst, and sent a notification to other observatories that were looking for gamma-rays. That happened twice – in July 2018 and January 2019, allowing two teams of astronomers to see two GRB events from the ground for the first time.