A huge one black hole in the early universe was spotted by an international team of astronomers to be… sleeping, after hearty food.

The researchers, led by the University of Cambridge, used the space telescope James Webb to locate this black hole in the early universe, dating back just 800 million years after the Big Bang.

The black hole is one of the most voluminous which have been discovered at this point in the development of the universe: its mass is 400 million times the mass of our Sun and constitutes about 40% of the total mass of the galaxy in which it is located. However, despite its gigantic size, this black hole “eats” the gas it needs to grow at a very low rate, about 100 times below its theoretical maximum, so it is essentially inactive.

This finding of a supermassive black hole so early in the universe’s evolution, yet not growing, calls into question existing models of how black holes grow. Publishing the research in the journal Nature, the scientists point out that the most likely scenario is that black holes go through short periods of extremely fast growth followed by long periods of inactivity.

When black holes “they are sleeping“, it is much less brightwhich makes them more difficult to detect. Despite its inertia, this particular black hole was detected due to its enormous size.

According to established models, black holes form from debris dead stars and they accumulate matter up to a predicted limit (Eddington limit). However, the sheer size of this black hole suggests that established models may not adequately explain how such black holes form and grow. “It is possible that black holes are born large, which could explain why James Webb detected massive black holes in the early universe. Another possibility is that they go through periods of hyperactivity, followed by long periods of inactivity.”says one of the study’s authors, Professor Roberto Maiolino, from the Kavli Institute of Cosmology at the University of Cambridge.

The researchers ran computer simulations to model how this dormant black hole could grow to such a large 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 rapidly, followed by long periods of inactivity. The researchers point out that black holes like this one probably eat for five to ten million years and sleep for about 100 million years.