Thermal Radiation and Planck Distribution — Charles Kittel & Herbert Kroemer
Physics — Statistical Mechanics · age-of-the-sun
Problem
Age of the Sun. Suppose 4×1026Js−1 is the total rate at which the Sun radiates energy at the present time. (a) Find the total energy of the Sun available for radiation, on the rough assumptions that the energy source is the conversion of hydrogen (atomic weight 1.0078) to helium (atomic weight 4.0026) and that the reaction stops when 10 percent of the original hydrogen has been converted to helium. Use the Einstein relation E=(ΔM)c2. (b) Use (a) to estimate the life expectancy of the Sun. It is believed that the age of the universe is about 10×109 years.