ASTR 3 Lecture Notes - Lecture 3: Photosphere, Chromosphere, Hydrogen Fuel
Document Summary
Black body is a perfect absorber and perfect emitter of radiation: curves are function of temp; hotter they are, further into the uv spectrum, we are black bodies, hotter the black body, the more energy. Stable star must be in hydrostatic equilibrium. Compensated by an increase in central temperature increase in luminosity. Present luminosity is 30% higher than when sun formed. Sun has now used approx. half of its fuel contained in the core. After 10 billion years luminosity will be 2-3 times higher than today: nuclear reactions in core will cease, hydrogen fuel will be exhausted, and the sun will become a red giant. R=0. 5 au: will end life as a white dwarf. R=10^-2 r (sub sun) = 1 r (sub earth) Mass of sun, size of earth (100x smaller than sun is now) Layer we see and call surface of sun is between photosphere and chromosphere. Density of gas increases as you move toward core.
