Radio galaxy, computer artwork. A radio galaxy is a type of active galaxy that is very luminous at radio wavelengths. An active galaxy is a typical galaxy, but with a core of emission in the middle of the galaxy, known as an active galactic nucleus (AGN). It is believed the radiation emitted from these is due to a central supermassive black hole attracting a large amount of material. In around 10% of active galaxies, the black hole and surrounding accretion disk produce narrow beams of energetic particles and magnetic fields, and eject them outward in opposite directions away from the disk. These are the radio jets (top left, bottom right), which emerge at nearly the speed of light.