Massive black hole in the early universe spotted taking a ‘nap’ after overeating

Like a bear devouring salmon before hibernating, or taking a much-needed nap after Christmas dinner, this black hole has eaten so much that it has become dormant in its host galaxy.

An international team of astronomers, led by the University of Cambridge, detected the black hole in the early universe just 800 million years after the Big Bang using the NASA/ESA/CSA James Webb Space Telescope.

The black hole is so massive – 400 million times more massive than the Sun – making it one of the most massive black holes Webb has discovered in the history of the universe. The black hole is so massive that it makes up about 40% of the total mass of its host galaxy: by comparison, most black holes in the local universe only make up about 0.1% of the mass of their host galaxy.

Yet despite its massive size, the black hole is gobbling up, or accreting, the gas it needs to grow at very low rates—roughly 100 times below its theoretical maximum limit—leaving it essentially dormant.

Such a supermassive black hole appeared early in the universe but did not grow, challenging existing models of how black holes develop. However, the most likely scenario is that the black hole undergoes a brief period of ultra-rapid growth, followed by a long period of dormancy, the researchers said. Their results were published in the journal nature.

When black holes “doze,” they are much less luminous, making them harder to detect, even with highly sensitive telescopes like Webb. Black holes cannot be observed directly, but they can be detected through the apparent light emitted by the rotating accretion disk that forms near the edge 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 dormant, its enormous size allows us to detect it,” said lead author Ignas Juodžbalis from the Kavli Institute of Cosmology at the University of Cambridge. “Its dormant state also tells us something about the mass of the host galaxy. The early universe managed to produce some absolute monsters, even in relatively small galaxies.”

According to the Standard Model, black holes form from the collapsed remnants of dead stars and accumulated material, reaching a predicted limit (called the Eddington limit) where radiation pressure on the material overcomes the black hole’s gravity. However, the massive size of this black hole suggests that the standard model may not fully explain how these monsters form and grow.

“It’s possible that black holes are ‘born big,’ which could explain why Webber discovered the massive black holes in the early universe,” said co-author Roberto Maio from the Kavli Institute and Cambridge’s Cavendish Laboratory Professor Lino said. “But another possibility is that they go through a period of hyperactivity, followed by a long period of dormancy.”

The Cambridge researchers, working with colleagues from Italy, conducted a series of computer simulations to model how this dormant black hole could have grown to such a huge size in the early universe. They found that the most likely scenario is that black holes can exceed the Eddington limit for short periods of time, during which they grow very rapidly, followed by long periods of inactivity: Black holes like this could eat It takes five to ten days.

“It sounds counterintuitive to explain a dormant black hole by a period of hyperactivity, but these brief bursts allow it to grow rapidly while dozing off most of the time,” Maiolino said.

Because dormant periods are much longer than superfast growth periods, it is during these periods that astronomers are most likely to detect black holes. “This was the first result I had during my PhD, and it took me a while to realize how brilliant it was,” Juodžbalis said. “It wasn’t until I started talking to colleagues in theoretical astronomy that I was able to see the true significance of this black hole.”

Dormant black holes are harder for astronomers to detect because of their lower luminosities, but researchers say that if a black hole in the early universe spent most of its time dormant, the black hole was almost certainly the tip of a much larger iceberg. .

“It’s likely that the vast majority of black holes are in this dormant state – I’m surprised we found this one, but I’m excited to think we’ll find more,” Maiolino said.

These observations are part of the JWST Advanced Deep Galactic Survey (JADES). The research was partly supported by the European Research Council and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).