Red dwarf

Schematic Hertzsprung-Russel diagram.
wikimedia

wikipedia tells

A red dwarf is a small and relatively cool star on the main sequence, either late K or M spectral type. They have a mass of less than half that of the Sun (down to about 0.075 solar masses, below which stellar objects are brown dwarfs) and a surface temperature of less than 4,000 K.

Red dwarfs are by far the most common type of star in the Galaxy, at least in the neighborhood of the Sun. Proxima Centauri, the nearest star to the Sun, is a red dwarf (Type M5, apparent magnitude 11.05), as are twenty of the next thirty nearest. However, due to their low luminosity, individual red dwarfs cannot easily be observed. From Earth, none is visible to the naked eye.
wikipedia

Timeless stars!

Stellar models indicate that red dwarfs with less than 35% of the Sun's mass are fully convective. Hence the helium produced by the thermonuclear fusion of hydrogen is constantly remixed throughout the star, avoiding a buildup at the core.

Red dwarfs therefore develop very slowly, having a constant luminosity and spectral type for some hundreds of billions of years, until their fuel is depleted. Because of the comparatively short age of the universe, no red dwarfs of advanced evolutionary stages exist in the current era.
wikipedia

Personally, I really love this awesome sentence cleverly written by an anonymous contributor to the wikipedia article:

Because of the comparatively short age of the universe, no red dwarfs of advanced evolutionary stages exist in the current era.