Diocese definition, an ecclesiastical district under the jurisdiction of a bishop. See more.
planetary nebulae represented here by the ring nebula are examples of emission nebulae an emission nebula is a nebula formed of ionized gases that emit light of various colors the most common source of ionization is high energy photons emitted from a nearby hot star
The Ring Nebula (M 57) is a <%= link_to 'planetary nebula', 'http://www.sun.org/encyclopedia/emission-nebula' %> about 2300 light years away from us. This is how it looks when a star blows its outer layers at the end ...