Supermassive black hole 'burps' reveal how big the cosmic monsters grow

Black hole feeding patterns may tell us more than how hungry they are.

Steph Panecasio
Steph Panecasio Former Editor
Steph Panecasio was an Editor based in Sydney, Australia. She knows a lot about the intersection of death, technology and culture. She's a fantasy geek who covers science, digital trends, video games, subcultures and more. Outside work, you'll most likely find her rewatching Lord of the Rings or listening to D&D podcasts.
2 min read

The way a supermassive black hole flickers may determine its size.

Mark A. Garlick / Simons Foundation

When you think about black holes, you probably don't tend to wonder if they're hungry. The idea of a hungrily feeding black hole is quite intimidating, I bet. Rest easy, however, because a black hole's eating pattern may help us better understand them.

A new study from the University of Illinois Urbana-Champaign published Thursday in the journal Science has revealed feeding supermassive black holes emit a noticeable flickering light, the pattern of which is directly related to their mass. 

When dormant, supermassive black holes are typically quite dull and don't emit much light. When active and feeding, however, they produce a pattern of flickering light we can detect from across the universe, ranging from hours to decades. 

"There have been many studies that explored possible relations of the observed flickering and the mass of the SMBH, but the results have been inconclusive and sometimes controversial," said Colin Burke, an astronomy graduate student and lead author of the study.

The team, led by Burke, analyzed the variability patterns to identify a characteristic timescale, allowing them to equate the flickering patterns with the mass of a supermassive black hole. When it comes to these active, feeding supermassive black holes, shorter timescales of flickering indicate a smaller black hole, while longer timescales indicate more massive black holes.

The researchers describe the flickering as the black hole equivalent of a burp. When we're infants, we typically burp a lot more. Adults however, are able to hold in the burp for longer (unless you're of the "better out than in" persuasion).

It's the burps that could help us come to terms with the relative sizes of not only supermassive black holes but also accreting white dwarfs and -- hopefully -- intermediate-mass black holes, or IMBHs, which are thought to have formed throughout the history of the universe but are rare and hard to find.

"Now that there is a correlation between the flickering pattern and the mass of the central accreting object, we can use it to predict what the flickering signal from an IMBH might look like," Burke said.