red star

noun Astronomy.

any star with a low surface temperature and a reddish color, as a red giant or a red dwarf.

Origin of red star

First recorded in 1900–05

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

One is the F. of hydrogen; another is the red-star line of Jupiter and Saturn.
History of Astronomy
George Forbes