Right now, a giant black hole that was born in the early years of the universe is doing something shockingly relatable: taking an extended nap after overeating. In a new study, researchers observed the black hole in a dormant state, having fallen asleep after consuming matter and undergoing a whirlwind period of growth. Its slumber, although uneventful, may deliver answers on the birth and growth of black holes.
An updated perspective on black holes drives the recently published Nature study, featuring a team of international astronomers, led by the University of Cambridge, that made the discovery through the James Webb Space Telescope. The black hole taking center stage in the study originated 800 million years after the Big Bang, early in the universe’s evolution.
What Makes a Black Hole Fall Asleep?
As the research team discovered, this black hole is also somewhat of an anomaly due to its staggering size, as it makes up roughly 40 percent of the total mass of its host galaxy. Meanwhile, the majority of black holes in the local universe only represent 0.1 percent of their host galaxy mass.
The primitive black hole, however, doesn’t currently possess a voracious appetite to match its immensity. At the moment, it’s only accreting the gas it needs to grow at about 100 times below the theoretical maximum limit of what it can eat. The lack of continuous growth has put it in a dormant state.
Black holes are often observable not directly, but by their accretion disc, a structure of hot gas and dust that gives off a bright glow. When they aren’t experiencing active growth, they become less luminous, and therefore harder to spot. Researchers noticed the dormant black hole, though, because of its massive size.
“Even though this black hole is dormant, its enormous size made it possible for us to detect,” said Ignas Juodžbalis, a lead author of the study from Cambridge’s Kavli Institute for Cosmology, in a statement. “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.”
Read More: Black Holes Eat Far More Voraciously Than We Previously Thought, and They Make a Mess
Explaining the Black Hole's Hunger
Seeing that it was sleeping, the researchers questioned how a black hole of this size and age could have developed.
Normally, black holes manifest from collapsed stars and grow by accreting matter up to such a maximum limit, called the Eddington limit, which strikes a balance between the pressure of radiation and the gravitational pull of the black hole. But this doesn’t explain how the giant, dormant black hole ballooned to its current size.
The most plausible answer, as proposed by the new study, is that black holes can experience bursts of hyperactive growth, followed by long periods of dormancy.
Using computer simulations to understand the black hole’s growth, they learned that it likely exceeded the Eddington limit for a brief time before falling into inactivity. The researchers say that black holes like this one may eat for 5 million years to 10 million years, and then sleep for about 100 million years. In November 2024, a separate study in Nature Astronomy revealed a black hole from 1.5 billion years after the Big Bang that similarly exceeded the Eddington limit — yet another sign that early-universe black holes may have consumed matter at rapid rates.
“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 Roberto Maiolino, an astrophysicist from the Kavli Institute and Cambridge’s Cavendish Laboratory, in a press release.
Although dormant black holes are not easily observable due to their low luminosities, researchers are determined that more cases exist across the universe, waiting to be found. With this pattern of swift growth and prolonged dormancy, the way black hole development is viewed could now receive a major overhaul.
“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.
Read More: Black Holes May Have Sped Up Star Formation After the Big Bang
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Nature. A dormant overmassive black hole in the early Universe
IFLScience. Black Hole Found Devouring Matter At A Rate 40 Times Greater Than The Eddington Limit
Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
