But black holes do have gravity, and they know how to use it. If a black hole has a stellar companion, and they orbit each other closely enough, the former can strip some of the gas from the star. The gas falling into the black hole heats up and shines in high-energy radiation. Astronomers have found more than 50 such systems in the Milky Way.
However, when a black hole and its companion star orbit each other at a greater distance, the star remains whole. The black hole is then dormant and much more challenging to spot. To find it, one has to search for wobbling stars whose peculiar motion could be due to an unseen dark companion.
This is how a team of astronomers discovered the newest black hole candidate, which they call Gaia BH1. (The study, which is under review, is available here). Although it isn’t the first proposed candidate of its kind, it seems to be the most compelling to date.
Comments are closed.