Black holes, once the preserve of theory and science fiction, are well-established inhabitants of the universe. Observations of the motions of stars orbiting the center of the Milky Way have proved beyond doubt that a black hole 4 million times as massive as the Sun resides there. Many other galaxies are thought to host similarly heavy or even heavier black holes at their centers. Scattered out beyond the center, there are thought to be millions of lighter, stellar-mass black holes, produced when the most massive stars collapse in on themselves at the end of their lives. This week, Science explores the current state of understanding of black holes with a series of Perspectives and Reviews.
Science 3 August 2012:
Vol. 337 no. 6094 p. 535