Veil nebula supernova remnant, optical image. This is part of the Veil nebula known as the Witch's Broom nebula, or NGC 6960. The nebula comprises shells of gas cast off during a supernova explosion around 15,000 years ago. A supernova is the death of a massive star in which its outer layers are blown into space at high speeds. The ejected shells impact the interstellar medium and the gases are ionised, causing them to emit light. Here the red regions are ionised hydrogen and the blue regions are ionised sulphur. The star 52 Cygni is seen at upper centre, but it is not related to the nebula. The Veil nebula lies around 1400 light years from Earth in the constellation Cygnus.