Wolf-Rayet stars are very hot, mass-rich and bright stars. Massive Wolf-Rayet stars have burned through their nuclear fuel at a prodigious rate and end this final phase of massive star evolution in a spectacular supernova explosion. They are shedding their outer envelopes in powerful stellar winds. At the same time their radiation is ionizing the gas and makes it glow. These beautiful figures as depicted above consist mostly of hydrogen and oxygen.Another example is the Crescent Nebula NGC 6888,also located in the constellation of Cygnus. The spectacle in the above picture is the bright, pink star at the centre of the frame (chain of 4 stars), accompanied by two blueish stars above and beneath. These stars are not related to the nebula. A closer look reveals that the arc is not only blue but pink as well. This indicates that it consists of oxygen and hydrogen gas. Also the background shows the veils of ionized hydrogen, omnipresent in the constellation of cygnus.

    
Distance estimates put WR 134 about 6,000 light-years away, making the frame over 200 light-years across. Wolf-Rayet stars conclude their lives in spectacular supernovae. The stellar winds and final supernovae enrich the interstellar material with heavy elements to be incorporated in future generations of stars.