Black hole spotting — the week in infographics
How to see a wandering black hole
Our first graphic shows how a team of astronomers has, for the first time, seen an isolated black hole wandering across the Milky Way. Lone black holes probably litter the Galaxy, but they’re extremely hard to spot. Black holes are typically glimpsed as they interact with other objects, such as companion stars.
To find a lone one, the team used a technique known as microlensing. The researchers looked for stars that appeared to brighten as an invisible object passed by, its gravitational pull bending and focusing the stars’ light like a lens. Very massive objects, such as black holes, affect a larger area of space and so brighten the star for longer. The team selected 8 candidate objects, which produced no light of their own but brightened a background star for at least 200 days, for further observations. The researchers now have enough data to assert that one is a black hole.