A powerful flash of cosmic light disrupted Earth’s atmosphere

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The giant gamma-ray flare, the brightest ever observed by astronomers, illuminated telescopes for seven minutes.

A burst of light with record energy, which reached Earth last year after traveling two billion light years through the cosmos, disrupted the upper atmosphere in an unprecedented way, according to a study published on Tuesday, November 14.

On October 9, 2022, astronomers discovered a gigantic burst of gamma rays, the most intense form of electromagnetic radiation, a phenomenon caused by the most extreme events in the universe, such as the explosions of giant stars.

This gamma-ray burst was nicknamed BOOT (“Brightest of all time»: «The brightest ever“), emitted from a distance of about two billion light-years, illuminated telescopes for only seven minutes but left residual light visible to amateur astronomers for seven hours.

The powerful lightning triggered lightning detectors in India and activated instruments intended for studying solar flares. Scientists were quickly able to determine its impact on long-wave radio communications in the lower part of the ionosphere (the upper layer of Earth’s atmosphere), between 60 and 350 km altitude.

Continuing to analyze the phenomenon, Italian and Chinese researchers noted for the first time that it had also affected the upper part of the same ionosphere. Located between 350 and 950 km above Earth, near the edge of space, the upper ionosphere is where radiation from the Sun is converted into charged particles that form a large electric field.

For about two decades, experts have debated the possibility that gamma-ray bursts could affect the upper ionosphere, Mirko Piersanti, lead author of the study published in Nature Communications, explained to AFP. “I think we have finally answered this question», said this researcher at the Italian University of L’Aquila.

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Erase“the ozone layer?

A stroke of luck for his team: the Chinese-Italian CSES satellite, equipped with an electric field detector, was located “right in the area illuminated by the gamma-ray burst», 500 km above the Earth. “We have found a shape in the electric field that has never been observed before», Specifies the researcher.

It’s amazing that we can see things that happen deep in space, but that also affect the Earth», Erik Kuulkers, gamma radiation expert at the European Space Agency (ESA), underlined in a press release. The discovery should help understand the potential threat of future gamma-ray bursts.

The worst-case scenario would be for such a powerful outburst to occur in our galaxy, the Milky Way. She would have the powererase completely» the Earth’s ozone layer, explains Mirko Piersanti. Everything on the surface would then be exposed to the sun’s ultraviolet rays, which could wipe out life on Earth.

But don’t panic, because it’s just as likely that the ionosphere absorbs all the gamma rays and that these “nothing happens» for earthlings, the researcher continues. The BOAT gamma-ray burst that occurred in our sky last year from the small constellation Arrow, officially called GRB 221009A, could be the result of the explosion of a massive star at the end of its life, or the birth of a black hole.

Or both, given its power: a giant star explodes and becomes a supernova, before collapsing in on itself to form a black hole. Matter then forms a disk around the black hole, is absorbed there and is released in the form of energy. On average, more than one gamma-ray burst hits Earth every day, but a burst of BOAT’s intensity is estimated to occur only once every 10,000 years.

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