This gorgeous, classic view of the Crab Nebula is actually a composite of 24 images. Colors indicate the different elements expelled when the star that created the nebula went supernova in 1054. Blue in the filaments in the outer part of the nebula represents neutral oxygen, green is singly-ionized sulfur, and red indicates doubly-ionized oxygen. The rapidly spinning neutron star embedded in the center of the nebula is the dynamo powering the nebula's eerie interior bluish glow.
Image by NASA, ESA, J. Hester and A. Loll (Arizona State University)