Using data from ESA’s Gaia astrometry mission, astronomers have identified the closest known black hole, less than 1600 light-years away from Earth and have determined its mass. The black hole is orbiting a star similar to our Sun, and was identified by tracking the star that the black hole is orbiting. It is expected to be the first one of many black holes to be discovered using the same method. At the same time, the properties of the binary star system are unexpected, indicating a serious gap in astronomers’ understanding of how such systems form in the first place.