An historic term for sunspot number. In 1849, R. Wolf of Zurich originated the general procedure for computing the sunspot number. The record of sunspot numbers that he began has continured to this da
y.
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 fro
m 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.
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 fro
m 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.