|
Mike,
The colour of a star has more to do with its surface temperature. As an analogy, consider a bunsen burner. A hot flame is bluish whilst a cooler flame is yellowish or reddish. The spectral class of a star correlates pretty well with its colour or surface temperature.
The one dimensional Harvard spectral classes were OBAFGKM in that order, with O class stars being hot blue stars (temperature 30000 to 60000 degs K), M class stars being cooler red stars (temperature 2000 to 3500 degs K).
The Morgan-Keenan spectral classification further subdivides each class from 0 to 9. A G9 star is cooler than a G0 star, which is closer to an F9 star.
A red M class star is not really that red, more orange. Carbon stars are much redder and this is actually due to a high level of carbon in the star's outer shell. The majority of carbon stars are old cooling giants or supergiants.
Regards, Rob.
|