The largest cosmic explosion ever documented was observed: more than ten times brighter than any supernova, lasting only a few months, but more than three years. Called AT2021lwx, it lies about 8 billion light-years from Earth thanks to the Zwicky transit facility in California. The discovery was published in the Monthly Notices of the Royal Astronomical Society by a team of astronomers led by the University of Southampton.
AT2021lwx was first spotted in 2020 and then followed by the Atlas telescope, which from Hawaii scans the night sky for rapidly changing brightness objects, such as supernovae, asteroids and comets. The researchers then decided to investigate the explosion further using other telescopes, such as Swift (a mission conducted by NASA in collaboration with Italy and the United Kingdom), the European Southern Observatory (ESO) New Technology Telescope in Chile and the Gran Telescopio of the Canary Islands in Spain.
The study shows that the explosion, which occurred when the universe was about 6 billion years old, could have been the result of a huge cloud of gas (thousands of times larger than the sun) that was destroyed by a supermassive black hole. Parts of the cloud would have been swallowed up, emitting shock waves through its remnants as well as into the large cake of dust surrounding the black hole. Such events are very rare and no one of this magnitude has ever been observed before.
Last year, the brightest burst ever observed was identified as a gamma-ray burst called GRB 221009A: although it was brighter than AT2021lwx, it lasted much less, so the total energy emitted was definitely less.
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