the other extreme, dwarfs of less than half the mass of our Sun (spectral type M) are likely to tidally lock planets within their habitable zone, along with other problems (see Habitability of red dwarf systems). While there are many problems facing life on red dwarfs, many astronomers continue to model these systems due to their sheer numbers and longevity. For these reasons NASA's Kepler Mission is searching for habitable planets at nearby main-sequence stars that are less massive than spectral type A but more massive than type M—making the most probable stars to host life dwarf stars of types F, G, and K. See also , survey of stars Explanatory notes References External links Libraries of stellar spectra by D. Montes, UCM Spectral Types for Hipparcos Catalogue Entries Stellar Spectral Classification by Richard O. Gray and Christopher J. Corbally Spectral models of stars by P. Coelho Stellar classification table Classification Concepts in astronomy