What is an M Dwarf Star?
Astronomers classify stars according to two physical properties: surface temperature and luminosity (energy emitted per second). The surface temperature can be determined by studying the spectrum of the star, i.e., the amount of energy it emits at different wavelengths (colors). Stars are grouped by temperature, from hottest to coolest, into “spectral classes” labeled: O, B, A, F, G, K, and M. In recent years, two more classes, L and T, have been added after M. An M star has a surface temperature of 2200 – 3500 K. (The Sun has a surface temperature of 5800 K.) Each of the classes is subdivided into ten intervals, 0 to 9. The Sun is a G2 star. The “luminosity class” indicates the stage of life for the star. Stars go through a process of “stellar evolution” as they age. Stars like the Sun are in the prime of their lives and generate energy by fusing hydrogen into helium in their cores. These stars are called “dwarfs” and are designated luminosity class V. (The Sun is a G2V star and has a
