Radio galaxies and their relatives, radio-loud quasars and blazars, are types of active galaxy that are very luminous at radio wavelengths. They have luminosities up to 1039 W between 10 MHz and 100 GHz.
The radio emission is due to the synchrotron process. The observed structure in radio emission is determined by the interaction between twin jets and the external medium, modified by the effects of relativistic beaming. Radio galaxies are almost exclusively large elliptical galaxies. Radio-loud active galaxies can be detected at large distances, making them valuable tools for observation. Recently, much work has been done on the effects of these objects on the intergalactic medium, particularly in galaxy groups and clusters.