No CrossRef data available.
Published online by Cambridge University Press: 30 March 2016
The activity of galactic nuclei entails a continuous release of energy in the form of hot gas, violent motions, relativistic particles and ordered magnetic fields. The spectrum radiated spans most of the electromagnetic band, from radiowaves to γ-rays, and the power can reach or exceed 10441 - 1046 ergs sec-1. Various extensive surveys dealing with this subject have been published recently (see, e.g., Hazard and Mitton 1979; Physica Scripta 1978; Setti 1976; Wolfe 1979): we refer the reader to these publications for details. In the following we shall just outline the main ideas which are being discussed to explain the origin of these phenomena which pose one of the most important problems of modern astronomy.