Astronomers have witnessed the biggest explosion in space.
The explosive event labeled AT2021lwx was observed to be ten times brighter than any other known. supernovathe explosions that occur so massive stars die. And while supernova explosions only last a few months, this explosive event has been going on for at least three years.
AT2021lwx is also three times brighter than the light emitted when stars are torn apart and devoured by supermassives. black holes, occurrences called “tidal disruption events” or “TDEs.” The explosion is about 8 billion light-years from Earth and therefore occurred when the universe was only 6 billion years old.
AT2021lwx was first detected by the Zwicky Transient Facility in California in 2020 and later picked up by the Hawaii-based Asteroid Terrestrial-impact Last Alert System (ATLAS). Both systems are designed to survey the night sky for astronomical events that change rapidly in brightness over time, also known as “transients.” This change in brightness can indicate a supernova or gamma-ray burst (GRB) deep in the universe or something much closer to home like a comet or asteroid.
Although it was detected by these facilities three years ago, the magnitude and power of the AT2021lwx explosion were unknown until now.
Related: What is a supernova?
“We came across this by chance, as our search algorithm flagged it when we were looking for a type of supernova,” Philip Wiseman, a researcher at the University of Southampton who led the research, said in an emailed statement. “Most supernovae and TDEs only last a couple of months before fading away. For something to be bright for more than two years was immediately very unusual.”
Wiseman and the team of astronomers believe that AT2021lwx may be the result of a black hole violently disrupting a gas cloud with a mass thousands of times greater than Sun. As it did so, the black hole swallowed fragments of the gas cloud, sending shock waves both into what was left of the gas and into a wider, donut-shaped dust toroid that surrounded it, causing them to emit bright radiation. electromagnetic.
Events like this have been witnessed before, they are rare. Also, none that have been witnessed before have been on the scale of AT2021lwx.
While AT2021lwx is actually not as bright as gamma-ray burst GRB221009A Detected by astronomers in 2022, this event that erupted 2.4 billion light-years away lasted just ten hours after detection. Although that’s quite long for a GRB, it means that AT2021lwx has emitted much more energy during its entire lifetime than this gamma-ray burst alone.
Measuring the power of a cosmic explosion
After its initial discovery, the team of researchers behind this discovery continued to examine AT2021lwx using several different telescopes, including the Neil Gehrels Swift Telescope, the New Technology Telescope in Chile, and the Gran Telescopio Canarias on La Palma, Spain.
After these observations, the researchers took the spectrum of light emitted by the event and divided it into its constituent wavelengths, measuring how light was emitted and absorbed around the event. This allowed the researchers to calculate the distance to the source of AT2021lwx.
“Once you know the distance to the object and how bright it appears to us, you can calculate the brightness of the object at its source,” team member and University of Southampton professor Sebastian Hönig said in the statement. “Once we did those calculations, we realized that this is extremely bright.”
The only thing in the known universe that is as bright as AT2021lwx are supermassive black holes. When these black holes feed on stellar gases that fall into them at high speeds, they can emit incredibly bright emissions known as quasars.
“With a quasar, we see the brightness flicker up and down over time,” added team member and University of Southampton professor Mark Sullivan. “But looking back for over a decade, there was no detection of AT2021lwx, then suddenly it appears as bright as the brightest things in the universe, which is unprecedented.”
Although there are other possible explanations for the explosive event, astronomers currently favor the explanation that sees an extremely large cloud of mostly gaseous hydrogen or dust being ejected from its orbit around the black hole and sucked into it. This will only be conclusively determined when the team has collected more data on AT2021lwx.
The team will now look at the explosion in different wavelengths of light, including X-rays. Doing so could reveal the temperature of the event and what processes are driving it. They will also run computer simulations to find out if their model of a titanic gas cloud punctuated by a black hole could explain AT2021lwx.
“With new facilities, such as the Vera Rubin Observatory’s Legacy Survey of Space and Time, coming online in the coming years, we look forward to discovering more events like this and learning more about them,” Wiseman concluded in the statement. “It could be that these events, while extremely rare, are so energetic that they are key processes in how the centers of galaxies change over time.”
The team’s research is discussed in a document (opens in a new tab) published in the Monthly Notices of the Royal Astronomical Society.