A
red giant is a luminous
giant star of low or intermediate mass (roughly 0.3–8
solar masses ) in a late phase of
stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, from 5,000 K and lower. The appearance of the red giant is from yellow-orange to red, including the
spectral types K and M, but also class S stars and most
carbon stars.