The largest cosmic explosion ever recorded. “I have never noticed anything like this. It seems to have come out of nowhere”

Astronomers announced on Friday the discovery of the “biggest” cosmic explosion ever recorded, a ball of energy 100 times larger than our solar system, which suddenly ignited three years ago, reports AFP.

Scientists have a novel explanation for the cause of the phenomenon, but insist that further research is needed to clarify this aspect.

The event, named AT2021lwx, is not the brightest ever recorded, however. The “record” is held by a gamma-ray burst GRB221009A (a colossal burst of energy during the collapse of a star), detected in October 2022 and considered to be the “brightest ever”.

But the explosion AT2021lwx, described in the magazine Monthly Notices of the Royal Astronomical Society in the UK, can be described as “the biggest” because it released infinitely more energy in three years than the gamma-ray burst, according to the study’s lead author, Philip Wiseman, an astrophysicist at the University of Southampton in the UK.

AT2021lwx is the result of an “accidental discovery”, he told AFP. The explosion was detected in 2020, automatically, by the American observatory Zwicky Transient Facility in California. But that detection “went unused in the observatory’s database,” according to Wiseman. Then, scientists noticed it the following year. A direct observation of the phenomenon changed the situation. Analysis of the light showed that it took eight billion years to reach the telescope.

Astronomers are still wondering what caused the phenomenon. It could be a supernova, that is, the explosion of a massive star that has reached the end of its life, but the brightness in the case of AT2021lwx is ten times greater than would be expected.

Another possibility is a tidal dismemberment event, when a star is torn apart by the gravitational forces of a black hole it has gotten too close to. But then again, the AT2021lwx is three times brighter to validate such a scenario.

The only known equivalent of the measured luminosity is that of quasars, galaxies that have at their center a supermassive black hole that is soaked with matter and emits a phenomenal amount of light. But the light from quasars is flickering, whereas in this case it suddenly became brighter three years ago.

“I have never noticed something like this (…). It seems to have come out of nowhere,” says researcher Philip Wiseman. His team has an idea, however, as the study points out. Their theory is that a giant cloud of gas, the size of 5,000 suns, is being devoured by a supermassive black hole.

As the principle of science is that “there are never certainties”, the team is working on new simulations – using the data they have – to test how plausible this theory can be.

The problem is that supermassive black holes should be found at the center of galaxies. And the one from the AT2021lwx event should be the size of our Milky Way. However, no one has yet detected a galaxy in the vicinity of the observed event. “It’s a real enigma,” says Philip Wiseman.

It remains for astronomers to look – in the sky and in the databases with astral observations – for similar events that could help clarify the explosion. (news.ro)