NGC 6888 (Crescent Nebula)

Constellation: Cygnus

Distance: 4700 light years

The Crescent Nebula is illuminated solely by the bright blue Wolf-Rayet star at its center. Wolf-Rayet stars are part of the evolution of supergiant type O stars, but are rare because this phase is short lived, typically ending in a supernova within a million years. The hydrogen in the Crescent Nebula was ejected from the star during its red giant phase, and was then dispersed by the strong stellar winds created by the Wolf-Rayet phase (a similar process creates the Bubble Nebula) . The residual gases are being ionized by the central star.