red dwarf

A red dwarf is a small main sequence star, generally an M-type star (M dwarf). Sometimes the term is used to include some or all main-sequence K-type stars (K dwarfs), but K dwarfs can be referred to as orange dwarfs. The red-dwarf mass range is from 0.075 to about 0.5 solar masses and their surface temperature is 2000-4000 K. Red dwarfs make up about 75% of the stars in the Milky Way, and many of the nearest stars are red dwarfs. They have become of interest in the search for habitable extra-solar planets because there are so many (thus, as a group, they host many planets), thus such a large number are close to us (making it easier to study their planets), and their relative dimness is conducive to direct imaging of the planets. On the other hand, they can be quite active and the habitable zone is close to the star, making otherwise-habitable planets less so. Red dwarf examples:

• AD Leonis
• Proxima Centauri
• AU Microscopii
• Barnard's Star
• G239-25
• GJ 1132
• Gliese 436
• K2-18b
• Kapteyn's Star
• Kepler-186
• Lacaille 9352
• Lalande 21185
• LHS 1140
• LHS 3844
• Luyten 726-8
• OGLE-2005-BLG-390L
• Ross 154
• Ross 248
• Scholz's Star
• Teegarden's Star
• TOI 700
• TRAPPIST-1
• Wolf 359