Hubble Space Telescope snapped this image of NGC 6624, a globular star cluster in Sagittarius. Observations over the past quarter-century suggest that a black hole at least 7,500 times the mass of the Sun inhabits the cluster’s center. It is one of the few possible intermediate-mass black holes discovered so far. [NASA/STScI]
Find out more in our radio program entitled Timing a Black Hole.