Zero Genie

By nature, black holes are impossible to see directly. But astronomers can sense their presence by the way they interact with their environments, letting us glimpse these objects whose gravity is so strong that nothing can escape. In the past century, not only have astronomers shown that black holes do exist, but they’ve found dozens in our own galaxy.

However, based on the number of stars in our galaxy, there should actually be tens of millions out there. The trouble is that, unless they’re near another star, they can be hard to detect. In these binary systems, a black hole can steal material from its companion star, generating distinct X-ray light in the process. A 2016 paper reported 77 nearby candidate black holes from such X-ray observations. We’ve curated a list of 10 of the closest black holes to Earth that astronomers know a little about.

Because of their shrouded nature, black holes are hard to study. So scientists are continually learning more about these objects and refining black holes’ known properties, particularly mass, as telescopes gather more evidence. The numbers listed here include astronomers’ current best estimates of these black hole properties.