Astrophysical black holes

Abstract

Black holes are exotic relativistic objects which are common in the Universe. It has now been realised that they play a major role in the evolution of galaxies. Accretion of matter into them provides the power source for millions of high-energy sources spanning the entire electromagnetic spectrum. Observations of stars orbiting close to the centre of our Galaxy provide detailed clear evidence for the presence of a 4 million Solar mass black hole. Gas accreting onto distant supermassive black holes produces the most luminous persistent sources of radiation observed, outshining galaxies as quasars. The energy generated by such displays may even profoundly affect the fate of a galaxy. We briefly review the history of black holes and relativistic astrophysics before exploring the observational evidence for black holes and reviewing current observations including black hole mass and spin. In parallel (and in italic)we outline the general relativistic derivation of the physical properties of black holes relevant to observation. Finally we speculate on future observations and touch on black hole thermodynamics and the extraction of energy from rotating black holes.