Two bright stars orbit an unseen black hole, in this artist's impression of the HR 6819 triple system. By Daniel CleryThe Milky Way galaxy is thought to contain hundreds of millions of black holes.
But only a few dozen have revealed themselves—through the x-ray glow of hot gases that surround them. Now, astronomers have found a “dark” black hole only 1000 light years away from Earth—just down the road in galactic terms.
It is the closest black hole to our planet ever found, in a star system that is visible to the naked eye. “They have good evidence,” says Todd Thompson, an astronomer at Ohio State University. “I believe them.”The invisible nature of most black holes frustrates astronomers, who can learn about this final stage of stellar