Black Holes in Active Galactic Nuclei

Abstract

There are two completely different astrophysical contexts in which black holes are believed to play an important role: (1) As members of stellar-mass binary systems and (2) as supermassive black holes in the nuclei of active galaxies and quasars. A black hole most vividly manifests itself when it accretes matter from a companion star or the surroundings. As the matter moves under the spell of the black hole’s gravity, it heats up to high temperatures and emits radiation. Rotational energy can also be extracted from a black hole through the medium of a magnetic field. Much of the energy released can appear in non-thermal form, and can be transported through relativistic beams, which give rise to startling phenomena like apparent faster than light motion, rapid variability and flux amplification.