The Ring Nebula, also known as M57 in the Messier Catalog
, or NGC
6720, is probably the most famous planetary nebula
of them all. It is located in the constellation Lyra
The inner regions of the nebula emits only ultraviolet radiation, while a bit further from the center it emits green light, from ionized oxygen and nitrogen. The outer regions consists mostly of hydrogen, giving off red light.
Unfortunately, it's not very bright, having a visual magnitude of 8.8, but one should be able to make it out with a good amateur telescope. But to see the magnificent colors and the real magic of this nebula, one needs a larger one. With a really good telescope one might even catch a glimpse of the central star, which is a white dwarf of magnitude 15.
The distance to the nebula isn't known. Estimations vary from 1,000-2,000 light years to over 5,000.
Recent research has revealed that the material in the nebula is not a spherical cloud after all, but more likely a torus, or perhaps even a cylinder. We just happen to be viewing it from one of its "poles".