Even a monstrous black hole needs a break after a cosmic feast, according to new findings by University of Cambridge astronomers.
The James Webb Space Telescope (JWST) has once again expanded our understanding of the universe, this time capturing behavior from a distant black hole that almost feels human. This enormous and ancient black hole lies at the very edge of our observable universe, so far away that the light from its early existence is only now reaching JWST’s lenses.
Ancient, Enormous, and Slumbering
The new JWST data reveals a black hole that was formed only 800 million years after the Big Bang, which occurred almost 14 billion years ago. It’s one of the largest black holes in the early universe known to science, coming in at a staggering 400 million times the mass of Earth’s Sun and 40% of the mass of its own galaxy.
Typically, a black hole contributes only about 0.1% of its galaxy’s mass. Yet, like a bear in hibernation after consuming its last meal of the year, this one is dormant, only consuming one-hundredth of its gas intake limit.
The black hole’s enormous size and dormancy conflict with the current understanding of how black holes develop. One potential solution offered in the latest research is that black holes do not grow steadily but experience massive growth periods followed by dormant periods.
Massive Yet Dim Black Hole
These dormant black holes lack the brilliance of their active counterparts, causing even the JWST to struggle when observing them. Since black holes are black against the blackness of space, astronomers can only observe the swirling ultraviolet glow of hot gasses around the event horizon. The low gas intake makes dormant black holes more difficult for astronomers to spot.
“Even though this black hole is dormant, its enormous size made it possible for us to detect,” said lead author and Cambridge researcher Ignas Juodžbalis. “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 tiny galaxies.”
Pushing Black Hole Boundaries
The standard model for black holes centers on the Eddington Limit. Astronomers generally accept that black holes result from the collapse of dead stars accreting matter up to the Eddington Limit when radiation provides enough pressure to overcome the black hole’s pull. The incredible size of this black hole, among other recent findings, raises serious questions about current models.
“It’s possible that black holes are ‘born big,’ which could explain why Webb has spotted huge black holes in the early universe,” commented co-author Professor Roberto Maiolino. “But another possibility is they go through periods of hyperactivity, followed by long periods of dormancy.”
Rethinking Black Hole’s Eddington Limit
The Cambridge team collaborated with Italian colleagues to develop computer simulations modeling the hole’s possible growth history. The most likely model featured a start-and-stop development cycle where the black hole exceeded the Eddington Limit in short bursts followed by lengthy dormant periods. They concluded that the black hole probably eats for about five to ten million years before it rests for roughly 100 million years. Due to how much more time black holes spend dormant, astronomers will most likely discover them in this state.
“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 Maiolino.
“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,” said Juodžbalis. “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.”
Black Hole Detection Gets Trickier
Due to their dimness, it’s much more challenging to discover black holes in this state. Since the new findings indicate that early black holes spend much of their time in a dormant state, this may be only the beginning, with many left to discover. Astronomers will have to adjust to a new standard of difficult-to-detect black holes.
“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,” said Maiolino.
The paper “A Dormant Overmassive Black Hole in the Early Universe” appeared on December 18, 2024 in the Nature.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.