Astronomers have just watched the most powerful explosion ever seen

Astronomers have spotted what may be the most powerful explosion ever seen. The gamma ray burst, called GRB221009A, was spotted on 9 October, and even its afterglow is brighter than most objects in the sky.

This type of gamma ray burst (GRB) is thought to occur when a massive star explodes in a supernova, leaving behind a black hole. The explosion creates an extraordinary jet of light which makes up the GRB itself, and then the supernova causes a dimmer afterglow. This particular GRB appears so bright partially because it is about 2.4 billion light years away from Earth, making it one of the closest GRBs ever spotted in addition to being the brightest.

“If we look at all of the gamma ray bursts that have been detected, this one stands apart,” says Jillian Rastinejad at Northwestern University in Illinois. “Informally, we’ve been calling it the BOAT – the brightest of all time.” She and her colleagues calculated that a GRB this bright is expected to occur only once every thousand years or so.

We don’t know exactly how powerful this burst is, though, despite the fact that many telescopes around the world are looking at it. That is partially because it is so bright that it saturates the detectors of gamma-ray telescopes, so all they see are completely white pixels with no detail, says Andrew Levan at Radboud University in the Netherlands, one of Rastinejad’s colleagues. “If you had gamma-ray eyes, you’d be blinded,” he says. Current estimates put the energy of the GRB between 10^54 and 10^55 ergs, he says – in contrast, the total energy released by the sun throughout its lifetime is expected to be about 10^51 ergs.

GRB221009A is so bright that it is affecting Earth, even from billions of light years away. Naval radio transmitters recorded a strange disturbance in the upper atmosphere, which seems to have been caused by the powerful light from the GRB slamming into it. Detectors that search for high-energy photons – particles of light – have also seen extraordinary particles with energies far higher than anything produced at the Large Hadron Collider.

This has made a splash among astronomers. “It seems like pretty much every telescope in the world is starting to look at it,” says Rastinejad. But to learn more about the supernova itself and its home galaxy, they will have to wait until the bright jet fades, which could take months. Once that occurs, we should have a better idea of why this GRB was so extraordinarily bright.

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