Today in Astronomy 142 - Astro Pas Rochester

Energy and the sun! Hydrostatic equilibrium and ideal-gas behavior ensurethat the center of the Sun is very hot, and energy (in theform of light) is radiated from the center.! The high opacity of the Sun to light determines the rate atwhich the energy leaks out. As we have seen, it takes along time for photons to diffuse from center to surface.! This cannot go on forever, without the Sun cooling down,or replacement for the energy that leaks away.! We know that the solar system is about 4.5x10 9 years old(from many radioisotope abundance measurements onmeteorites), and that life has existed here for at least 3x10 9years. Thus the Sun must have had close to its presentluminosity for billions of years.Astronomy 142 25