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 spectrum of a reflection nebula is similar to that of the star or stars illuminating the nebula. Reflection nebulas are smaller and fainter than emission nebulas; the luminosities of the responsible stars are tens of times greater than those of the nebulas.