Veil nebula supernova remnant (NGC 6960), optical image. This wisp of glowing gas is part of a much larger spherical shell called the Cygnus Loop. The shell comprises stellar material ejected in a supernova, the explosive death of a massive star. The supernova forming this shell is thought to have occurred between 5-8000 years ago. The gas was cast off into space at high speeds, and when it impacted the interstellar medium it compressed and heated it, forming a glowing plasma. The bright star at upper right is 52 Cygni, which is unrelated to the supernova. The distance to the nebula is a matter of debate, with estimates ranging from 1400 to 2600 light years. It lies in the constellation Cygnus.