NGC 6888, the Crescent Nebula, is located in the constellation Cygnus near the bright star Sadr. The emission nebula, also designated Caldwell 27 and Sharpless 105) was discovered in 1792 by William Herschel. Located 5000 light years from Earth, the emission nebula is a product of the impact of shock waves from the stellar wind of red giant HD192163 colliding with the star's ejecta when it became a red giant. The star is likely to go supernova sometime soon