A ball of energy a hundred times the size of our solar system. Astronomers announced Friday the discovery of the "largest" cosmic explosion ever recorded, a ball of energy that suddenly lit up three years ago. Scientists have not yet found explanations for the cause of the phenomenon, but they insist on the imperative of continuing research to clarify the matter.
The event, cataloged AT2021lwx, can be described as the "largest" because it released infinitely more energy in three years than the gamma-ray burst detected in October 2022, according to the lead author of the study published in the journal Monthly Notices of the British Royal Astronomical Society, Philip Wiseman, an astrophysicist at the British University of Southampton.
A team of astronomers led by researchers at @unisouthampton have discovered the largest cosmic explosion ever witnessed. đź’Ą
Known as AT2021lwx, it is more than 10x brighter than any known supernova. The research is published in Monthly Notices of the Royal Astronomical Society. pic.twitter.com/LWaX4mbuWx
— Royal Astronomical Society (@RoyalAstroSoc) May 12, 2023
AT2021lwx is the result of an "accidental discovery". The explosion had certainly been detected in 2020, automatically, by the American observatory Zwicky Transient Facility in California. But that detection "went unused in the database," Wiseman said. Before scientists noticed it the following year.
"We have never seen such a thing"
Direct observation of the phenomenon has changed the situation. Analysis of the light established that it took eight billion years to reach the telescope. Astronomers are still wondering about the cause of the phenomenon. It could be a supernova, the explosion of a massive star at the end of its life, but the luminosity here is ten times greater than expected.
Another possibility is a tidal rupture event, in which a star is torn apart by the attractive forces of a black hole to which it has come too close. But then again, AT2021lwx is three times too bright to validate such a scenario. The measured brightness has no equivalent known except with that of quasars, these galaxies sheltering in their heart a supermassive black hole that gorges itself with matter by emitting a phenomenal amount of light. "We have never observed such a thing (...). It appeared out of nowhere," says the scientist.
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His team does have an idea, set out in the study. His theory is that a gigantic cloud of gas, the size of 5,000 suns, is being devoured by a supermassive black hole. Since the principle of science is that there are "never certainties," the team is working on new simulations — using the data — to test the "unavoidable plausibility" of their theory.
The problem is that supermassive black holes are thought to be at the center of galaxies. And that the one of the AT2021lwx event should be a size equivalent to our Milky Way. However, no one has yet detected a galaxy in the vicinity of the observed event. According to Philip Wiseman, "it's a real enigma."