Transcript: The Stephan-Boltzmann Law says that the luminosity of a star is proportional to its surface area and the fourth power of the temperature. If the luminosity is in watts, the radius is in meters, the temperature is in Kelvins, then the constant of proportionality, the Stefan-Boltzmann constant, is 5.67 times 10-8. This means that a star with twice the area has twice the luminosity, twice the number of photons emitted per second, but a star with twice the temperature has 24 or sixteen times the luminosity, sixteen times as much light emitted per second. So hotter stars emit more light per second and more light per unit area.