Gas: It’s what’s for dinner. At least that was the case for a black hole in the early universe, which had to take a break after eating too much nearly 13 billion years ago.
The black hole is 400 million times the mass of the Sun, as seen using the cutting-edge Webb Space Telescope. Webb can see some of the earliest light in the universe by observing light at near- and mid-infrared wavelengths, helping it cut through clouds of interstellar dust to see fainter, more distant light sources. According to a team of astronomers that studied the black hole, it’s essentially dormant despite its young age—putting conventional models of black hole growth to task. The researchers published their findings today in Nature.
“Even though this black hole is dormant, its enormous size made it possible for us to detect,” said Ignas Juodžbalis, a researcher at the University of Cambridge’s Kavli Institute for Cosmology, and lead author of the study, in a university release. “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.”
Black holes are thought to form from collapsed stars, and their intense gravitational fields amass matter around them. The matter swirling around the black hole glows, and is called an accretion disk. Occasionally, matter falls into the gaping maw of the black hole, causing a brilliant flash of light—this is how the black hole feeds.
Black hole accretion disks are filled with morsels for astronomers eager to better understand how the objects from which light cannot escape turn into some of the densest and most massive entities in the cosmos. In 2021, a team published a study on a star stuck in a doom loop with a black hole. In 2022, a different team saw a black hole puke up a star years after eating it. This year, a team determined that the fastest-growing black hole consumes a Sun per day and a separate team accurately forecast the snack schedule of a black hole 50 million times the mass of our Sun about 860 million light-years from Earth.
There are two fundamental differences between that snacking black hole and the one recently investigated in Webb data. For one, the most recently studied black hole is way, way larger, making up about 40% of the total mass of its host galaxy. And the crux of the issue: The more recently studied black hole is hardly eating, switching up previously held ideas about black hole evolution.
“It’s possible that black holes are ‘born big’, which could explain why Webb has spotted huge black holes in the early universe,” said study co-author Roberto Maiolino, a researcher with the Kavli Institute and Cambridge’s Cavendish Laboratory, in the same release. “But another possibility is they go through periods of hyperactivity, followed by long periods of dormancy.”
The idea is that black holes accrete material rapidly, and briefly exceed the predicted limit for their size. Then, the gravitational behemoths sit back and relax for about 100 million years before gorging themselves on more of the cosmos.
Black holes are difficult objects to study; besides their extreme physics, there’s the obvious issue of them not emitting light. Thankfully, scrutinizing the objects’ shadows and their effects on surrounding matter—including the accretion disk—enables astronomers to build better models simulating some of the most extreme physics that space has to offer.
