Transcript: A cool main sequence star with a temperature of about three thousand Kelvin lies on the main sequence with a luminosity of about a hundredth the luminosity of the Sun and a size about a quarter the Sun’s size, but there are stars with the same temperature, or color, as the Sun that are much more luminous, up to ten thousand times the luminosity of the Sun or even more. Betelgeuse and Antares are two well known examples. Application of the Stephan-Boltzmann Law shows that these stars must have sizes that are several hundred times the Sun’s size. These are called red giant stars.