An Etymological Dictionary of Astronomy and Astrophysics

An expanding cloud of debris from the explosion of a → Type I supernova in the → constellation  → Taurus. Its light reached Earth in 1054 and
was visible to the naked eye even in the daytime. Lying about 6,300 → light-years away, the Crab nebula is an intense → radio source (Tau A), and also a source of X-rays and gamma-rays. The diameter of the → supernova remnant is about 6 light-years; it is expanding at velocity of 1000 km/sec.

See also: → crab; → nebula.