https://phys.org/news/2018-05-image-black-hole-bounty-captured.html

Theoretical studies of the dynamics of stars in galaxies have indicated that a large population of stellar mass black holes—as many as 20,000—could drift inward over the eons and collect around Sgr A*. This recent analysis using Chandra data is the first observational evidence for such a black hole bounty.

A black hole by itself is invisible. However, a black hole—or neutron star—locked in close orbit with a star will pull gas from its companion (astronomers call these systems "X-ray binaries"). This material falls into a disk and heats up to millions of degrees and produces X-rays before disappearing into the black hole. Some of these X-ray binaries appear as point-like sources in the Chandra image.

                                                            
                                    
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