Galaxy nuclei activity

The possible nature of activity of galactic nuclei is discussed. Many galactic nuclei contain compact sources of radiation of variable intensity the size of which is <=1018-1019 cm. The intensity variability observed in the optic and X-ray range prove that the most part of high-frequency radiation in the continuous spectrum is formed in regions with a small size. It is supposed that the energy source of active nuclei is the gravitation energy of collapsed objects. Substance accretion on the central object (accretion models) or energy removal in the form of large-scale electromagnetic fields from magnetosphere of rotating supermassive objects (electrodynamic models with substance outflow) are considered as mechanisms of separating gravitation energy. The assumption is made that the activity of galactic nuclei is one of the most important problems of modern astronomy