Hubble searches for nearby intermediate black hole.

Astronomers using the Hubble Space Telescope have found a strong candidate for an intermediate-sized black hole, weighing roughly 800 solar masses, at the heart of the closest globular star cluster to Earth, located 6,000 light-years away. The suspected object can't be seen, but its mass is calculated by studying the motion of stars caught in its gravitational field. Hubble's unique capabilities have been used to zero-in on the core of the globular star cluster Messier 4 to go black-hole hunting with higher precision than in previous searches.