This is the Medusa Planetary Nebula. It’s in the constellation Gemini and is about 1500 light years distant. It’s very old, very large and very dim (magnitude 16). The Medusa is roughly 12,000,000 times dimmer than the brightest star of the evening sky (Sirius at magnitude -1.4).
Planetary Nebulas are star remnants of stars similar in size to our own Sun. At the end of a medium star’s life it turns into a red giant and expels most of its material in the form of an expanding shell rich in carbon, nitrogen, oxygen and calcium. The radiation from the core remnant ionizes these materials and causes the shell to radiate.
Image META information