Wiktionary
n. (context star English) any of a class of red giant stars having a high proportion of carbon because of helium burning
Wikipedia
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 most 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.
Carbon stars have quite distinctive spectral characteristics, and they were first recognized by their spectra by Angelo Secchi in the 1860s, a pioneering time in astronomical spectroscopy.
Usage examples of "carbon star".
It seemed a per feet hideout, with all trails to Jijo quantum collapsed but one, and that one passing through the atmosphere of a giant carbon star.
Those patrons were called Buyur, and they came from Galaxy Four--from a world with a huge carbon star in its sky.