NEBULAE & STAR CLUSTERS 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 Cassiopeia A (3C 461) The supernova remnant associated with Cas A The strongest radio source in the sky, apart from the Sun. Cassiopeia A is associated with the second youngest known supernova remnant (after G1.9+0.3) in the Milky Way Galaxy. Cas A lies about 10,000 light-years away in Cassiopeia (R.A. 23h 23.4m, Dec. +58° 48.9') and coincides with a shell-type remnant of a Type II supernova whose light reached Earth in about 1667. Optically, it is a faint nebula, 10 light-years across, with an expansion velocity of about 800 km/s and a mass of a few solar masses. It is also an extended source of soft X-rays. Related category    • NEBULAE AND STAR CLUSTERS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP