A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses (M☉)) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere 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.
The most common red giants are the so-called red-giant-branch (RGB) stars whose shells are still fusing hydrogen into helium in a shell surrounding a degenerate helium core. Other red giants are: the red clump stars in the cool half of the horizontal branch, fusing helium into carbon in their cores via the triple-alpha process; and the asymptotic-giant-branch (AGB) stars burning a helium shell outside a degenerate carbon–oxygen core, and sometimes also a hydrogen shell closer to the surface of the star.
The nearest red giant is Gamma Crucis, 88 light years away, but the orange giant Arcturus is described by some as a red giant and it is 36 light years away.
Read more about Red Giant: Characteristics, Evolution, Well Known Examples, The Sun As A Red Giant
Famous quotes containing the words red and/or giant:
“Who dreamed that beauty passes like a dream?
For these red lips, with all their mournful pride,
Mournful that no new wonder may betide,
Troy passed away in one high funeral gleam,
And Usna’s children died.”
—William Butler Yeats (1865–1939)
“The sense of death is most in apprehension,
And the poor beetle that we tread upon
In corporal sufferance finds a pang as great
As when a giant dies.”
—William Shakespeare (1564–1616)