An M dwarf is a small M-type star. The term red dwarf includes M dwarfs, but sometimes also includes small K-type stars (K dwarfs). Early M dwarfs (at the hotter end of the scale) are now considered likely places to observe extra-solar planets within a habitable zone. An estimate is about a quarter would have such a planet, but another reason is that M dwarfs are very common. But given their evolution, such planets are more likely to have experienced a longer period of stellar activity, giving it time to remove the planet's atmosphere. Examples include AD Leonis, Barnard's Star, Lacaille 9352, Lalande 21185, Ross 154, Ross 248, Scholz's Star, and Wolf 359.