M57 - Ring Nebula
[M57 - the Ring Nebula] is one of the best examples of planetary nebulae (PNe) in the sky.. A planetary nebulae is the end point in the life of a star. Medium and low mass stars, like the Sun eventually run of material to fuse in the stellar core. The object expands, as a means to achieve equilibrium and as the internal temperature changes their can be energetic events that cause an expanding gaseous shall to be form around the central star. The gas is then illuminated by the remaining white dwarf star. The Ring Nebula is some [2,300 light years] from the Earth. Thus its angular extent is quite small and to get any vague idea of the shape of the object requires a telescope and a dark site.
