Science News

Astronomers survey chorus of black holes belting out X-rays

All across the cosmos are the “songs” of black holes — the X-rays that radiate outward as black holes accrete and swallow matter. Recently, astronomers with California Institute of Technology identified a chorus of black holes while analyzing data collected by NASA’s Nuclear Spectroscopic Telescope Array.

Scientists call the radiation emitted by a black hole its “song.” Telescopes and their handlers have become rather adept at locating black holes with modest songs, but until recently, those that really belt it out have been hard to find.

NuSTAR is changing that, helping astronomers begin to fill in the high-energy X-ray background.

“We’ve gone from resolving just 2 percent of the high-energy X-ray background to 35 percent,” Fiona Harrison, an astronomy professor at Caltech and principal investigator of NuSTAR, explained in a news release. “We can see the most obscured black holes, hidden in thick gas and dust.”

Harrison is the lead author of a new study on a chorus of X-ray emitting black stars, soon to be published in the Astrophysical Journal.

Extra luminous black holes are those with a healthy supply of material to pull in and consume. The bigger a black hole gets, the stronger its gravity. The stronger a black hole’s gravity, the more material it can pull in. As matter accumulates around a black hole, it’s squeezed into the accretion disk and super heated, causing the region to glow with X-ray emissions.

Until recently, telescopes have struggled to differentiate the glow of X-rays from different sources.

“Before NuSTAR, the X-ray background in high-energies was just one blur with no resolved sources,” said Harrison. “To untangle what’s going on, you have to pinpoint and count up the individual sources of the X-rays.”

NuSTAR is helping astronomers get a more detailed picture of black holes and their surroundings, revealing what exactly is responsible for the louder portions of the cosmic background and how these singers are evolving over time.