Artwork of a red dwarf star emitting a stellar flare. A red dwarf is a small and relatively cool star on the main sequence, either late K or M spectral type. They range in in mass from a low of 0.075 solar masses to about 50% of the Sun and have a surface temperatures of less than 4,000 K. Red dwarfs are by far the most common type of star in the Milky Way, at least in the neighbourhood of the Sun, but due to their low luminosity, individual red dwarfs cannot easily be observed. From Earth, not one is visible to the naked eye.