A record-energy flash of light that reached Earth last year after traveling 2 billion light-years through the cosmos destroyed the upper layers of the atmosphere in an unprecedented way, according to a study published Tuesday.
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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.
Nicknamed BOAT (“Brightest Ever”), this gamma-ray burst, emitted at a distance of about two billion light-years, illuminated telescopes for just seven minutes but left residual light visible to amateur astronomers for seven hours.
The powerful flashes activated lightning detectors in India and triggered instruments used to study solar flares.
Scientists were able to quickly determine its impact on longwave radio communications in the lower part of the ionosphere (the upper layer of Earth’s atmosphere), between 60 and 350 kilometers above sea level.
By further analyzing the phenomenon, Italian and Chinese researchers discovered for the first time that it had also affected the upper part of the same ionosphere.
The upper ionosphere is located between 350 and 950 kilometers above Earth, near the edge of space. There, the sun’s radiation is converted into charged particles that form a large electric field.
For around twenty years, 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, tells AFP.
“I think we have finally answered this question,” commented this researcher from Italy’s University of L’Aquila.
“Delete” the ozone layer?
A stroke of luck for his team: the Chinese-Italian CSES satellite, equipped with an electric field detector, was located “exactly in the zone illuminated by the gamma-ray burst,” 500 km above Earth.
“We have found a shape in the electric field that has never been observed before,” explains the researcher.
“It’s incredible, we can see things that happen in space but also have an impact on Earth,” said Erik Kuulkers, a gamma ray expert at the European Space Agency (ESA), in a press release.
The discovery should help understand the potential threat from future gamma ray bursts.
The worst scenario would be that such a massive eruption would occur in our galaxy, the Milky Way. It would have the power to “completely destroy” 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 will absorb all the gamma rays and “nothing will happen” to Earthlings, the researcher continued.
The BOAT gamma-ray burst that occurred in our sky last year in the small constellation of Arrow, officially called GRB 221009A, could come from either 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 goes supernova before collapsing in on itself to form a black hole. Matter then forms a disk around the black hole, is absorbed there and released in the form of energy.
On average, more than one gamma-ray burst hits Earth every day, but a burst with the intensity of BOAT is estimated to occur only once every 10,000 years.