NGC 6888, the Crescent Nebula, is an emission nebula that surrounds WR136 (HD 192163), a magnitude 7.4 Wolf-Rayet star in the constellation of Cygnus.

Although it looks somewhat like a supernova remnant like IC 443, it is actually a relatively rare nebula surrounding a Wolf-Rayet star.

The nebula is a gigantic bubble of gas formed by the stellar wind from the extremely hot and massive young central star. The strong ultraviolet light from the star ionizes the gas and illuminates the nebula.

The Wolf-Rayet star will probably end up exploding in a supernova.

NGC 2359, Thor's Helmet, and NGC 7635, the Bubble Nebula, are two other examples of this type of nebula.

The nebula subtends an apparent angle of 18 x 13 arcminutes and is 26 light-years across. It is located 5,000 light-years from Earth.

NGC 6888 was discovered by William Herschel in 1792.

North is to the top in the above image.

NGC 6888 Catalogs: NGC 6888, LBN 203 Common Name: Crescent Nebula Object Type: Emission Nebula Magnitude: 10b Size: 18' x 13' Constellation: Cygnus Image Field Centered At: RA: 20h 12m 27s Dec: +38° 27' 12"