Extragalactic double radio sources—the current observational and theoretical position

Abstract

Abstract Recent high resolution observations of powerful double radio sources have revealed both compact high brightness regions and extended low brightness regions, as well as complex polarization structure. This is consistent with the view that the sources have their energetic origins in the compact nuclei of galaxies and quasars and that energy must be supplied continuously during the source's active lifetime. Possible models involving either the formation of two antiparallel beams of hot plasma or the ejection of massive objects are discussed.