so the Earth and the other terrestrial planets would be quickly vaporized. The smallest, least massive main sequence stars are about 1000 times dimmer than the Sun. If one of these stars replaced the Sun, the Earth’s temperature would fall to about 50 K, approximately the temperature of Pluto. The spectral types, temperatures, radii, and luminosities for main sequence stars of various masses are given in Table 19-1. In Table 19-1, masses, radii, and luminosities are given in terms of those of the Sun (M☉, R☉, and L☉).