Class M stars are by far the most common. About 76% of the main-sequence stars in the Solar neighborhood are class M stars.
Because main-sequence stars of spectral class M have such low luminosities, none are bright enough to be visible to see with the unaided eye unless under exceptional conditions.
Although most class M stars are red dwarfs, the class also hosts most giants and some supergiants such as VY Canis Majoris, Antares and Betelgeuse. Proxima Centauri, the nearest star to the Sun, is a red dwarf (Type M5).
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, from 5,000 Kelvin and lower.
50 giant planets have been discovered around giant stars. However these giant planets are more massive than the giant planets found around solar-type stars.
While other, more massive stars only burn through the hydrogen at their core before coming to the end of their lifetimes, red dwarfs consume all of their hydrogen, in and out of their core. This stretches the lifetime of red dwarfs out to trillions of years, far beyond the 10-billion-year lifetime of sun-like stars.
History of the Future
Habitable planets can be found orbiting Class M stars.