APOD 2.8: "Jellyfish Nebula"

This usually faint, elusive nebula, which looks much more like a brain than a jellyfish to me, is part of a supernova remnant known as IC 443. It forms a debris cloud, from an enormous star that exploded. Light from the explosion reached Earth 30,000 years ago- although I should like to review how astronomers find this out. This nebula is located near a bright star called Eta Geminorum, in the constellation Gemini. It is about 5,000 light years away, and it is a "complex environment."