Astronomers have witnessed the biggest explosion in space.
The explosive event labeled AT2021lwx was observed to be ten times brighter than any known supernova, the explosions that occur as massive stars die. And whereas supernova explosions only last a couple of months, this explosive event has been raging for at the least three years.
AT2021lwx can also be 3 times brighter than the sunshine that’s emitted as stars are ripped apart and devoured by supermassive black holes, occurrences called “tidal disruption events” or “TDEs.” The blast is around 8 billion light-years from Earth and thus occurred when the universe was just 6 billion years old.
AT2021lwx was first spotted by the Zwicky Transient Facility in California in 2020 and was then picked up by the Asteroid Terrestrial-impact Last Alert System (ATLAS) based in Hawaii. Each of those systems are designed to survey the night sky for astronomical events that rapidly change in brightness over time, also often called “transients.” This modification in brightness can indicate a supernova or a gamma-ray burst (GRB) deep within the universe or something much closer to home like a comet or an asteroid.
Though it was spotted by these facilities three years ago, the sheer scale and power of the explosion AT2021lwx were unknown until now.
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“We got here upon this by likelihood, because it was flagged by our search algorithm after we were looking for a kind of supernova,” University of Southampton research fellow Philip Wiseman, who led the research, said in an emailed statement. “Most supernovae and TDEs only last for a few months before fading away. For something to be vivid for 2 plus years was immediately very unusual.”
Wiseman and the team of astronomers think that AT2021lwx stands out as the results of a black hole violently disrupting a cloud of gas with a mass 1000’s of times greater than the sun. Because it did so, the black hole swallowed fragments of the gas cloud, sending shockwaves into each what stays of the gas and right into a wider donut-shaped torus of dust surrounding it, causing them to emit vivid electromagnetic radiation.
Events like this have been witnessed before, they’re rare. What’s more, none which have been witnessed previously have been on the size of AT2021lwx.
While AT2021lwx is not actually as vivid because the gamma-ray burst GRB 221009A spotted by astronomers in 2022, this event that erupted from 2.4 billion light-years away lasted for just ten hours after detection. Regardless that that is sort of long for a GRB, it implies that AT2021lwx has put out way more energy over its entire lifetime than this gamma-ray burst did in its own.
Measuring the facility of a cosmic explosion
Following its initial discovery, the team of researchers behind this discovery continued to look at AT2021lwx using several different telescopes including the Neil Gehrels Swift Telescope, the Recent Technology Telescope in Chile, and the Gran Telescopio Canarias in La Palma, Spain.
Following these observations, the researchers took the spectrum of sunshine that was emitted from the event and split it down into its constituent wavelengths, measuring how light was emitted and absorbed across the event. This allowed the researchers to calculate the space to the source of AT2021lwx.
“Once you recognize the space to the thing and the way vivid it appears to us, you possibly can calculate the brightness of the thing at its source,” team member and University of Southampton professor Sebastian Hönig said within the statement. “Once we might performed those calculations, we realized this is amazingly vivid.”
The one thing within the known universe that’s as vivid as AT2021lwx are supermassive black holes. When these black holes feed on stellar gases that fall into them at high velocities, they will let off incredibly vivid emissions often called quasars.
“With a quasar, we see the brightness flickering up and down over time,” team member and University of Southampton professor Mark Sullivan added. “But looking back over a decade there was no detection of AT2021lwx, then suddenly it appears with the brightness of the brightest things within the universe, which is unprecedented.”
Though there are other possible explanations for the explosive event, the astronomers currently favor the reason that sees an especially large cloud of mostly gaseous hydrogen or dust that was knocked from its orbit across the black hole and sucked into it. This can only be conclusively determined when the team has collected more data about AT2021lwx.
The team will now have a look at the explosion in numerous wavelengths of sunshine including X-rays. Doing so could reveal the temperature of the event and what processes are driving it. They will even conduct computer simulations to find if their model of a titanic gas cloud disrupted by a black hole could account for AT2021lwx.
“With recent facilities, just like the Vera Rubin Observatory’s Legacy Survey of Space and Time, coming online in the subsequent few years, we hope to find more events like this and learn more about them,” Wiseman concluded within the statement. “It may very well be that these events, although extremely rare, are so energetic that they’re key processes to how the centers of galaxies change over time.”
The team’s research is discussed in a paper (opens in recent tab) published within the journal Monthly Notices of the Royal Astronomical Society.