Discovery of the largest cosmic explosion ever seen

Observed the largest cosmic explosion ever documented so far: more than ten times brighter than any supernova, it lasted not only a few months, but more than three years. Named AT2021lwx, it was located almost 8 billion light-years from Earth thanks to the Zwicky Transient Facility in California. The discovery is published in the journal Monthly Notices of the Royal Astronomical Society by a team of astronomers led by the University of Southampton.

AT2021lwx was first detected in 2020 and then followed by the Atlas telescope, which from Hawaii monitors the night sky for objects that rapidly change brightness, such as supernovae, asteroids and comets. The researchers then decided to further investigate the explosion with other telescopes, such as Swift (mission conducted by NASA in collaboration with Italy and the United Kingdom), the New Technology Telescope of the European Southern Observatory (ESO) in Chile and the Gran Telescopio Canarias in Spain.

The explosion, which occurred when the Universe was about 6 billion years old, could be the result of a vast cloud of gas (thousands of times larger than the Sun) that was violently destroyed by a supermassive black hole. Fragments of the cloud would have been swallowed, emitting shock waves through their remains as well as in the large dust doughnut surrounding the black hole. Such events are very rare and never before has one of this magnitude been observed.

Last year the brightest explosion ever seen was detected, a gamma ray called GRB 221009A: although it was brighter than AT2021lwx, it lasted much less, so the overall energy emitted was much lower.