Credit: Image: ESA/Hubble, NASA; Science: NASA, ESA, Eduardo Vitral (STScI)
A Hubble Space Telescope image of the globular star cluster, Messier 4. The cluster is a dense collection of several hundred thousand stars. Astronomers suspect that an intermediate-mass black hole, weighing as much as 800 times the mass of our Sun, is lurking, unseen, at its core.