About Stars: Wolf-Rayet Stars

Spectral class: WN, WC

These are very hot and blue stars with surface temperatures of 25 000 - 50 000 kelvin and a mass in the beginning of 25 times solar. Only a few hundred are known in our galaxy. WR stars cast away quickly large parts of their hull into space. Therefore in very big telecsopes they look similar to planetary nebulae.
Before the Wolf-Rayet phase they have been red supergiants or LBV which now expose their core. Supposably every star with enough mass goes through the Wolf-Rayet stadium. These stars are short before an explosion as supernova (astronomically that is. Those stars can as well still live for another several thousand years).

The very strong stellar wind is caused by a heightened accumulation of heavy elements on the surface. These block the light on its way out and therefore heat up the star, which powers the wind. The stellar wind can blow away up to one solar mass every 10 000 years.

Example: WR 124