by An example of an entirely new type of cosmic explosion that outnumbers supernovas would be the result of a small or medium-sized black hole destroying a star.
The burst, which has been named AT2022aedm, was spotted coming from a red galaxy located about 2 billion light-years from Earth by astronomers using the ATLAS network of robotic telescopes in Hawaii, Chile, and South Africa. It was quickly recognized as unprecedented.
“We’re always looking for things that are unusual and different from the normal types of supernovas, of which we find hundreds or thousands every year,” said Matt Nicholl, the team leader behind the discovery and an astrophysicist at Queen’s. University of Belfast, told Space.com. “AT2022aedm stood out because it was one of the brightest bursts we’ve ever seen, and it was one of the fastest to turn off after its peak.”
The explosion observed by Nicholl and team produced over 100 times more energy than the average supernova. And, while supernovas fade over months, Nicholl noted that AT2022aedm faded to 1% of its original brightness in just 14 days, then disappeared entirely. That means that, in just two weeks, AT2022aedm has released as much energy as the sun will in its 10 billion year lifetime.
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It is no wonder why the AT2022aedm sent a surprise to the group and found its own category, with the scientists behind the discovery describing it as the first “Luminous Fast Cooler” or “LFC”. That name emphasizes the characteristics of the explosion and Nicholl and his colleagues’ love of the English Premier League football club Liverpool Football Club, which also goes by the abbreviation “LFC.”
I think the most promising explanation for LFCs like AT2022aedm are models that include star annihilation. black hole“, said Nicoll.
This was the conclusion he and his colleagues reached by eliminating some of the prime suspects.
Strange suspects: How the finger pointed at destructive black holes
One of the first steps Nicholl and the University of Belfast scientists took was to eliminate some of the common problems of cosmic catastrophe.
The explosion was not seen as a supernova, as it was very powerful and very fast, but the place where it came from helped distinguish this LFC as something completely new.
One of the most common types of supernova is a core-collapse supernova formed when massive stars with masses 8 times that of the Sun run out of nuclear fusion fuel. Star clusters cannot fight gravity and eventually collapse. This leaves behind a black hole or neutron star in the heart of the star as it decays from the outer layer of the star.
“AT2022aedm can’t be a normal supernova collapse because the galaxy it’s seen in has very old stars with low masses; it doesn’t have eight times the mass of the Sun, and that’s what you need to have to get a supernova,” Nicholl said.
Alternatively, another common interstellar explosion, a Type-Ia supernova, occurs when the remnants of stars called white dwarfs strip material from a companion star. This deprivation of matter suggests a white dwarf above the mass limit required to trigger a supernova and create a neutron star or black hole, but these events create the same radiation output. For this reason, astronomers call them “common candles” and use them to accurately measure cosmic distances.
The AT2022aedm, however, doesn’t look like those at all.
That led the team to point the finger at black holes. But even then, they managed to eliminate the usual suspects.
Large black holes are being cleaned up
Events that see black holes rip apart stars and then eat away at the stellar remnants are rare, but not unknown. Astronomers have seen many examples of these so-called “Tidal Disruption Events” or “TDEs” and the light emitted during the violent process.
TDEs usually occur when a star gets too close to a supermassive black hole that sits at the heart of a galaxy. This black hole could be millions, or even billions, of times our sun. The gravitational effects of these black hole monsters generate massive tidal forces in their star bodies that stretch and compress the bodies of the stars, tearing them apart in a process called “spaghettification.”
However, Nicholl and his colleagues immediately realized that this LFC could not be the result of any TDA driven by a supermassive black hole. Again, this is partly due to where LFC appears to be coming from. Supermassive black holes sit at the heart of galaxies, and Nicholl said AT2022aedm was spotted far from the center of our home galaxy. This means that a small black hole (not at the heart of the galaxy) could be the cause of this LFC.
“If you had a low-mass black hole in a dense cluster of stars, and one of those stars is very close to the black hole, and the black hole is 10 to 100 times more massive, the sun might be able to tear itself apart and eat one of the stars,” he continued.
Nicholl added that he and the team have yet to rule out a more interesting suspect, however.
There is still the possibility that the LFC could be a function of an “intermediate mass,” or an intermediate black hole that sits between stellar black holes and supermassive black holes, ranging from 100 to a few thousand times their mass. of the sun.
This is an exciting prospect not only because medium-sized black holes remain rare, but also because studying them could help explain how supermassive black holes grew to such terrifying sizes early in the universe’s history.
“Intermediate black holes are expected to eat stars, and they don’t have to be at the center of galaxies because they could be ejected from a supermassive black hole,” Nicholl said. “LFCs can be associated with central black holes, and if so, they will give us a new way to try to find and respond to central black holes.
“This is the most important thing you can do in terms of trying to understand how massive black holes get.”
The team has already made great progress in its LFC research, searching archived data to find two “cold cases” like AT2022aedm, which show that this type of powerful cosmic explosion has been seen before but was buried in the data and probably missed.
Nicholl’s next step is to investigate globular clusters, which are incredibly dense groups of stars that can provide the conditions needed for small or medium-sized black holes to destroy a star and fuel an LFC.
Even if the research is successful, the thrill of discovering something completely new is unlikely to be lost on the astronomer.
“We’ve been looking at the sky for a long time, and sometimes people think we’ve seen everything there is,” Nicholl concluded. “I think things like this are really exciting because they remind us that nature still has a lot of amazing things waiting for us, and when we build a new telescope, we will find new things, and that will help us understand our nature.” better.”
The team’s research was published September 1 in The Astrophysical Journal Letters.
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