Betelgeuse is a very large, luminous and cool star classified as a red supergiant of M2Iab class.

Consequently, cool stars do not occupy the entire 3-dimensional parameter space of (mass, age, period), but instead define a 2-dimensional surface in this space.

It is a cool star, with estimates of its surface temperature ranging from 2200 to 2700 Kelvin.

It is stable only as a diatomic gas and has been found naturally in cool stars.

The second image combined two deep red colors to highlight the smoother distribution of older, cooler stars.

Apparently a nova is a close binary system, made up of a cool, normal star and a White Dwarf.

The vision faded, and Frodo found that he was looking at the cool stars twinkling in the silver basin.

The thing is, Firstsun, as they call their primary, is a cool red star.

La Superba's temperature is believed to be about 2800 K, making it one of the coolest true stars known.

Many other cool low-mass stars for which the Sun is included have a similar mechanism going on across their surface layers.