Astronomers Capture the Biggest Cosmic Explosion Ever: “A Fireball 100 Times Bigger Than the Solar System” | Sciences

Astronomers first noticed the explosion at Zwicky’s Transian facility in California in 2020. Zwicky astronomers scanned the starry sky for sudden increases in brightness that could indicate cosmic events such as supernovae or passing asteroids and comets. The small flash went unnoticed at first, but when the scientists checked all the observations and could calculate the distance of the flash, they realized they had caught an incredibly rare event.

AT2021lwx, as the explosion was called, appears to be caused by a huge cloud of gas, thousands of times more massive than our Sun, that collapsed into a supermassive black hole. Located 8 billion light-years from Earth, it is 10 times brighter than known supernovae. Moreover, the eruption has been going on for three years now.

“We estimate that it is 100 times the size of the solar system with a luminosity of about 2 trillion times that of the sun,” said Philip Wiseman, an astronomer at the University of Southampton. “In three years, this event released about 100 times as much energy as the Sun in its 10 billion years of age.”

“When I told our team these numbers, everyone was shocked,” Wiseman said. “Once we understood how very bright it was, we had to try to make sense of what it was.”

This phenomenon was a long way from being an exploding star, so astronomers looked at another possible cause for the bright flash of light in the sky: tidal disturbance. In addition, the star gets too close to the black hole, causing it to tear itself apart as it were. Then part of the star is swallowed up, and the rest is “stretched” into a column swirling around the black hole.

However, simulations of this scenario suggested that a star of up to 15 times the mass of the Sun would be needed to explain AT2021lwx. “It’s very rare to see such a large star, so we think the possibility of a much larger cloud of gas is more likely,” Wiseman explains.

Supermassive black holes are usually surrounded by a huge “cake” of gas and dust, and astronomers speculate that some of this material may have been broken down, perhaps by a galaxy collision, and sent inward. As matter spirals toward the black hole’s event horizon (its spherical outer boundary), it would release massive amounts of heat and light, illuminating and heating part of the donut to 12-13,000°C.

AT2021lwx is not the brightest phenomenon ever observed. An even brighter gamma-ray burst known as GRB 221009A was seen last year, but it only lasted a few minutes. On the one hand, the new event is still going on, which means more energy is released.