What is a Wolf-Rayet star ?
A Wolf-Rayet star is a very massive star, with a surface temperature between 25,000 and 50,000 K, luminosity from 100,000 to 1 million times the Sun’s and a mass from 10 to 50 times the Sun’s. The star Gamma Velorum is just such a star. What happens under these conditions of high luminosity and high temperature is that the light from the star itself produces radiation pressure which ejects large quantities of matter from the star. This heated matter can be seen in the spectra of these stars as bright ’emission lines’, rather than the dark absorption lines that most often are found in stars with the same surface temperatures…the so-called O-type stars. Wolf-Rayet stars are probably within a few million years of exploding as a supernova because of their very rapid evolution at such large masses.
