The most common type of star in the Milky Way galaxy is a red dwarf. Red dwarfs are stars with low mass and low luminosity, and they emit most of their light in the red part of the visible spectrum. They are the smallest and coolest type of stars that are able to sustain nuclear fusion in their cores. Red dwarfs are very numerous, and they make up about 70-80% of all the stars in the Milky Way galaxy.