Huge black hole detected in earliest universe

Dec. 18 () –

Cambridge-led astronomers have detected a supermassive black hole in the early universe with the James Webb Space Telescope, just 800 million years after the Big Bang.

As reported in ‘Nature’ The black hole is enormous (400 million times the mass of our Sun), making it one of the most massive black holes discovered by the Webb at this point in the development of the universe. The black hole is so huge that it represents approximately 40% of the total mass of its galaxy host: By comparison, most black holes in the local universe have about 0.1% the mass of their host galaxy.

However, despite its gigantic size, this black hole is consuming, or accumulating, the gas it needs to grow at a very slow rate (about 100 times below its theoretical maximum limit), which makes it essentially inactive.

Such a massive black hole so early in the universe, but not growing, challenges existing models of how black holes develop. However, researchers say the most likely scenario is that black holes go through short periods of ultrafast growth, followed by long periods of inactivity.

When black holes are “asleep,” they are much less luminouswhich makes them more difficult to detect, even with highly sensitive telescopes like the Webb. Black holes cannot be observed directly, but are detected by the telltale glow of a rotating accretion disk, which forms near the edges of the black hole. The gas in the accretion disk becomes very hot and begins to glow and radiate energy in the ultraviolet range.

“Although this black hole is inactive, its enormous size allowed us to detect it,” details lead author Ignas Juodzbalis of the Kavli Institute of Cosmology in Cambridge. “Its dormant state also allowed us to learn about the mass of the host galaxy. “The early universe managed to produce some absolute monsters, even in relatively small galaxies.”

According to standard models, black holes form from the collapsed remains of dead stars and accumulate matter up to a predicted limit, known as the Eddington limit, where the radiation pressure on the matter exceeds the gravitational pull of the hole. black. However, the large size of this black hole suggests that standard models may not adequately explain how these monsters form and grow.

“Black holes may have been born large, which could explain why Webb detected huge black holes in the early universe,” argues co-author Professor Roberto Maiolino of the Kavli Institute and the Cavendish Laboratory in Cambridge. “But another possibility is that they go through periods of hyperactivity, followed by long periods of inactivity.“.

Collaborating with colleagues in Italy, the Cambridge researchers ran a series of computer simulations to model how this dormant black hole could have grown to such a massive size so early in the universe. They found that the most likely scenario is that black holes can exceed the Eddington limit for short periods, during which they grow very quickly, followed by long periods of inactivity: the researchers say that black holes like this They probably eat for five to ten million years and sleep for about 100 million years.

“It seems contradictory to explain an inactive black hole with periods of hyperactivity, but these short bursts allow it to grow rapidly while it spends most of its time sleeping,” Maiolino points out.

Because dormancy periods are much longer than ultrafast growth periods, it is during these periods that astronomers are most likely to detect black holes. “This was the first result I got as part of my PhD, and it took me a while to appreciate how extraordinary it was.“Adds Juodzbalis. “It wasn’t until I started talking to my colleagues on the theoretical side of astronomy that I was able to see the true importance of this black hole.”

Because of their low luminosity, dormant black holes are harder for astronomers to detect, but researchers say this black hole is almost certainly the tip of a much larger iceberg, if black holes in the early universe pass the mark. most of its time in an inactive state.

“It is likely that the vast majority of black holes are found in this dormant state. I am surprised that we found this one, but I am excited to think that there are many more that we could find,” concludes Maiolino.