​Closest Known Black Hole to Earth Identified Using ESA’s Gaia | Astronomy Knowledge

​Closest Known Black Hole to Earth Identified Using ESA’s Gaia Astrometry Mission.

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 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.

Black holes are difficult to observe, by their definition: mass concentrated in a region with a diameter so small that the resulting extremely strong gravity allows nothing to escape, not even light. Still, these objects have long found their place in astrophysics. So-called stellar black holes, in particular, with a few solar masses, are the end state of very massive stars. Now, a group of astronomers led by Kareem El-Badry (Max Planck Institute for Astronomy [MPIA] and Harvard-Smithsonian Center for Astrophysics) has used a novel method to discover the closest known black hole. The discovery also shows up gaps in current astronomical knowledge, namely about the formation of binary star systems.