A carbon star is a late type star similar to a red giant (or
occasionally to a red dwarf) whose atmosphere contains more
carbon than oxygen; the two elements combine in the upper layers
of the star, forming carbon monoxide, which consumes all the
oxygen in the atmosphere, leaving carbon atoms free to form
other carbon compounds, giving the star a "sooty" atmosphere and
a strikingly ruby red appearance. In normal stars (such as the
Sun), the atmosphere is richer in oxygen than carbon. Ordinary
stars not exhibiting the characteristics of carbon stars but
cool enough to form carbon monoxide are therefore called oxygen-
rich stars. Astrophysical mechanisms  Carbon stars are explained
by more than one astrophysical mechanism. Classical carbon stars
are distinguished from non-classical ones on the grounds of
mass, with classical carbon stars being the more massive. In the
classical carbon stars, those belonging to the modern spectral
types C-R and C-N, the abundance of carbon is thought to be a
product of helium fus