An emission nebula in Cygnus, formed by the fast stellar wind from the Wolf-Rayet star WR 136 colliding with the slower wind the same star ejected when it was a red supergiant. That collision compresses the gas into a bright, crescent-shaped shell roughly 25 light-years across, about 5,000 light-years from Earth. The result is one of the most visually dramatic examples of a wind-blown bubble in the sky.

WR 136 is a ticking clock — massive Wolf-Rayet stars like it are in the final stages before a supernova. When it eventually explodes, the Crescent Nebula will be swept away entirely. In narrowband imaging, the nebula shows striking filamentary detail along the shock front where the two winds meet.