Cosmic explosion last year may be ‘brightest ever seen’

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<span>Photograph: Soheb Mandhai/PA</span>
Photograph: Soheb Mandhai/PA

A cosmic explosion that blinded space instruments last year may be the brightest ever seen, according to astronomers.

The blast took place 2bn light years from Earth, producing a pulse of intense radiation that swept through the solar system in October last year.

The cosmic event, known as a gamma-ray burst (GRB), produced some of the strongest and brightest explosions in the universe, triggering detectors on multiple spacecraft.

The October blast was deemed so exceptional that astronomers said it was the brightest of all time since the beginning of human civilisation.

Dr Dan Perley, of the Astrophysics Research Institute at Liverpool John Moores University, who followed the event with the university’s Liverpool telescope on the Spanish island of La Palma, said: “There is nothing in human experience that comes anywhere remotely close to such an outpouring of energy. Nothing.”

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Though they last mere seconds, GRBs produce as much energy as the sun will emit during its entire lifetime.

Perley said the event, dubbed GRB 221009A, produced “a phenomenal amount of energy”, adding: “It’s certainly the highest value ever recorded for a gamma-ray burst.”

The explosion blinded most gamma-ray instruments in space, meaning astronomers could not measure the real intensity of the emission, the like of which occurs once every 10,000 years.

Scientists had to reconstruct its energy expenditure from past and present data, with the analysis of 7,000 GRBs suggesting that GRB 221009A is 70 times brighter than any yet seen.

According to the European Space Agency, the blast deposited about a gigawatt of power into the Earth’s upper atmosphere – the equivalent of a power station’s energy output.

Astronomers believe GRB 221009A is a result of a massive star collapsing in on itself to form a black hole.

Perley added: “The star would have been many times more massive than the sun, probably 20 times as massive or more.”

GRBs also produce a supernova but astronomers are yet to ascertain whether that occurred in this case.

It is thought that GRB 221009A was so bright because it was much closer to Earth compared with other known GRBs and the beam of electromagnetic radiation happened to be pointing in the direction of the planet.

Andrew Levan, a professor of astrophysics at Radboud University in Nijmegen, the Netherlands, said: “We cannot say conclusively that there is a supernova, which is surprising given the burst’s brightness.

“If it’s there, it’s very faint. We plan to keep looking, but it’s possible the entire star collapsed straight into the black hole instead of exploding.”

GRBs are usually followed by a shock wave that emits lower energy radiation, known as an afterglow, that gradually fades over time.

The findings were reported in two separate papers in the Astrophysical Journal and Astrophysical Journal Letters.