The Crab Nebula is the remnants of a supernova explosion, which occurred in the year 1054 and was recorded by Chinese and Japanese astronomers at the time. It is approximately 6500 ly away, 6 ly wide and is still expanding.
Its name is derived from its appearance in early drawings made of it by Lord Rosse in 1844. This image was composed by the Hubble Space Telescope in 1999/2000 and the various colours denote different elements blown out when the parent star exploded. Blue in the filaments in the outer part of the nebula represents neutral oxygen, green is singly-ionised sulphor, and red indicates doubly-ionized oxygen.