| Term: | Wolf-Rayet stars |
| Definition: |
A type of very luminous, very hot (as high as 50,000 K) stars whose spectrum is characterized by broad emission lines (mainly He I and He II), which are presumed to originate from material ejected from the star at very high (~ 2000 km s^-1) velocities. The most massive O stars (M > 25 solar masses for solar metallicity) become W-R stars around 2 and 3 million years after their birth, spending only some few hundreds of thousands of years (≤ 10^6 years) in this phase until they explode as type Ib and type Ic supernovae. The minimum stellar mass that an O star needs to reach the W-R phase and its duration is dependent on metallicity. |