GALAXIES A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z           HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site Centaurus A (NGC 5128) The second strongest extragalactic radio source in the sky (after Cygnus A) and the nearest radio galaxy to the Milky Way; it lies in the constellation Centaurus, 13 to 15 million light-years away in the M83 group of galaxies. Cen A’s optical counterpart, discovered by James Dunlop in 1826, is an unusual elliptical galaxy (NGC 5128) bisected by a dark circumgalactic dust belt that appears to be debris from a merger between the elliptical and at least one spiral galaxy over the past few billion years. At radio wavelengths, Cen A show two vast lobes of radio emission, that extend thousands of light-years in opposite directions along the polar axis of the disk of NGC 5128. The most active radio emission, however, is associated with Cen A’s compact core which is the foremost example of a radio-loud active galactic nucleus and, at only 10 light-days across, the smallest known extragalactic radio source. Infrared measurements have revealed high-speed motions in this core that indicate a fast-spinning disk containing some 200 million solar masses of material. These data confirm a previous suspicion that the active nucleus of Cen A is powered by a supermassive black hole with a mass of about 100 million solar masses. Related category    • GALAXIES Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP