Unexpected Discovery: Hubble Space Telescope Uncovers Concentration of Small Black Holes

Scientists were expecting to find an intermediate-mass black hole at the heart of the globular cluster NGC 6397, but instead they found evidence of a concentration of smaller black holes lurking there. New data from the NASA/ESA Hubble Space Telescope have led to the first measurement of the extent of a collection of black holes in a core-collapsed globular cluster. Globular clusters are extremely dense stellar systems, in which stars are packed closely together. They are also typically very old — the globular cluster that is the focus of this study, NGC 6397, is almost as old as the Universe…