Changes

The first Wolf-Rayet stars were identified in 1867 at the [[Paris]] Observatory when astronomers '''Charles Wolf''' and '''Georges Rayet''' observed three stars in the constellation of [[Cygnus]] that displayed unusually broad emission bands in their [[spectrum]].  The cause of these emission bands remained unknown for several decades.  At first, the emission bands were thought to be some unusual state of hydrogen, but were later shown to be helium, an element identified for the first time in 1868.<ref>http://adsabs.harvard.edu/abs/1912MNRAS..73...62F</ref>  Later, emission lines of [[carbon]], [[oxygen]], and [[nitrogen]] were identified in the spectra.<ref>http://adsabs.harvard.edu/abs/1933Obs....56..196B</ref>

The first Wolf-Rayet stars were identified in 1867 at the [[Paris]] Observatory when astronomers '''Charles Wolf''' and '''Georges Rayet''' observed three stars in the constellation of [[Cygnus]] that displayed unusually broad emission bands in their [[spectrum]].  The cause of these emission bands remained unknown for several decades.  At first, the emission bands were thought to be some unusual state of hydrogen, but were later shown to be helium, an element identified for the first time in 1868.<ref>http://adsabs.harvard.edu/abs/1912MNRAS..73...62F</ref>  Later, emission lines of [[carbon]], [[oxygen]], and [[nitrogen]] were identified in the spectra.<ref>http://adsabs.harvard.edu/abs/1933Obs....56..196B</ref>

Later observations showed the usually wide emission bands were due to the [[Doppler effect]] caused by the gas surrounding the [[star]] moving at extremely high speeds of around 300-2400 km/s.<ref>http://adsabs.harvard.edu/abs/1929MNRAS..90..202B</ref>  The [[International Astronomical Union]] in 1938 classified Wolf-Rayet stars officially according to their spectra.  These classifications are WN, for spectrum dominated by lines of nitrogen, and WC for spectrum dominated by carbon and oxygen.<ref>http://adsabs.harvard.edu/abs/1942ApJ....95..112S</ref>  Later in 1990, the WN classification was subdivided into two sub-catagories called WNL and WNE.<ref name="nz">http://www.peripatus.gen.nz/astronomy/wolraysta.html</ref>

Later observations showed the usually wide emission bands were due to the [[Doppler effect]] caused by the gas surrounding the [[star]] moving at extremely high speeds of around 300-2400 km/s.<ref>http://adsabs.harvard.edu/abs/1929MNRAS..90..202B</ref>  The [[International Astronomical Union]] in 1938 classified Wolf-Rayet stars officially according to their spectra.  These classifications are WN, for spectrum dominated by lines of nitrogen, and WC for spectrum dominated by carbon and oxygen.<ref>http://adsabs.harvard.edu/abs/1942ApJ....95..112S</ref>  Later in 1990, the WN classification was subdivided into two sub-categories called WNL and WNE.<ref name="nz">http://www.peripatus.gen.nz/astronomy/wolraysta.html</ref>

==Portrait==

==Portrait==