One definition is synonymous with stellar M dwarfs ( M-type main sequence stars), yielding a maximum temperature of 3,900 K and 0.6 M ☉. There is some overlap with the properties of brown dwarfs, since the most massive brown dwarfs at lower metallicity can be as hot as 3,600 K and have late M spectral types.ĭefinitions and usage of the term 'red dwarf' vary on how inclusive they are on the hotter and more massive end. These red dwarfs have spectral types of L0 to L2. The coolest red dwarfs near the Sun have a surface temperature of about 2,000 K and the smallest have radii about 9% that of the Sun, with masses about 7.5% that of the Sun. According to some estimates, red dwarfs make up three-quarters of the stars in the Milky Way. Proxima Centauri, the nearest star to the Sun, is a red dwarf, as are fifty of the sixty nearest stars.

From Earth, not one star that fits the stricter definitions of a red dwarf is visible to the naked eye.

However, as a result of their low luminosity, individual red dwarfs cannot be easily observed. Red dwarfs are by far the most common type of star in the Milky Way, at least in the neighborhood of the Sun. Proxima Centauri, the closest star to the Sun, at a distance of 4.2 ly (1.3 pc), is a red dwarf.Ī red dwarf is the smallest and coolest kind of star on the main sequence.

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