Massive black hole is seen taking a 'nap' after eating too much

Black holes, among the most powerful forces in the universe, sometimes surprise us by taking it easy.

Consider the case of a giant black hole discovered in the early universe, found in a rare state of rest after a dramatic growth spurt.

Spotted quietly hibernating after consuming vast amounts of cosmic matter, it’s the celestial equivalent of a bear dozing off after feasting on salmon.

This unusual phenomenon sheds light on the mysterious life cycles of black holes, challenging our understanding of their behavior and growth in the early cosmos.

Nap time for an overfed black hole

The giant black hole, found just 800 million years after the Big Bang, is an extraordinary discovery.

Its size is an astronomical 400 million times the mass of our Sun, or roughly 40% of the total mass of its host galaxy. This is a stark contrast to most black holes, which usually account for about 0.1% of their host galaxy’s mass.

Interestingly enough, the gargantuan black hole isn’t continually feasting to maintain its size. Instead, it’s nibbling on its gas supply at a snail’s pace – about 100 times slower than its theoretical maximum limit.

Growth spurts followed by hibernation

The existence of such a monstrous, yet lazy, black hole in the early universe has scientists scratching their heads.

Researchers from the University of Cambridge suggest that this black hole must experience ultra-fast growth spurts followed by long hibernations.

Contrary to their vibrant and active cousins, napping black holes are less luminous, hence more challenging to spot.

In fact, black holes are not directly visible. Their presence is confirmed by the glowing accretion disc, a swirling formation near the black hole’s edges.

The gas in this disc becomes extremely hot and begins to radiate energy, making it possible to detect.

The slumbering giant challenges existing models

Study lead author Ignas Juodžbalis is an expert in Cambridge’s Kavli Institute for Cosmology.

“Even though this black hole is dormant, its enormous size made it possible for us to detect. Its dormant state allowed us to learn about the mass of the host galaxy as well. The early universe managed to produce some absolute monsters, even in relatively small galaxies,” noted Juodžbalis.

Traditional models suggest that black holes form from dead star remnants and accumulate matter up to a limit known as the Eddington limit.

However, the sheer size of this particular black hole suggests that standard models may not adequately explain how these cosmic monsters form and grow.

Hyperactive black hole needs a nap

The researchers speculate that black holes might either be born big, or they go through periods of hyperactivity, followed by long periods of dormancy.

To support this theory, the team conducted a range of computer simulations. The results suggested that black holes likely eat for five to ten million years and “nap” for about 100 million years.

“It sounds counterintuitive to explain a dormant black hole with periods of hyperactivity, but these short bursts allow it to grow quickly while spending most of its time napping,” said study co-author Roberto Maiolino.

Given the longer periods of dormancy, astronomers are more likely to spot black holes during these inactive phases.

“This was the first result I had as part of my PhD, and it took me a little while to appreciate just how remarkable it was. It wasn’t until I started speaking with my colleagues on the theoretical side of astronomy that I was able to see the true significance of this black hole,” said Juodžbalis.

Dormant black holes in the early universe

Detecting dormant black holes is a challenging task due to their low luminosity. However, this recently detected black hole hints at a potentially larger population of dormant black holes in the early universe.

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

The full study was published in the journal Nature.

Image Credit: Jiarong Gu

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