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Unformatted text preview: Stars • Stars have a range of intrinsic luminosities and temperatures (colour) • Correlations between colour and luminosity tell the story of stellar evolution. • Intrinsically faint stars are much more common than bright stars • The Solar luminosity is 3.8x10 26 W ¾ This is enough energy to melt a block of ice 1AUx1kmx1km in only 0.1 s. ¾ If the luminosity of the Sun has been approximately constant, the total energy released since its formation would be 4.8x10 43 J. • The surface temperature of the sun is about 5700 K ¾ The central temperature is inferred to be much higher: about 10 million K • This means the Sun is a fairly ordinary, main sequence star. Stellar Structure • Gas pressure in the stellar interior opposes gravity to keep the star in equilibrium • The equation of hydrostatic equilibrium equates the pressure gradient to the gas density. 2 r GM dr dP r ρ − = , where M r is the total mass within radius r. • The gas density and enclosed mass are related by the conservation of mass: ρ π 2 4 r dr dM r = • The density, pressure and temperature are related by the equation of state, which can usually be approximated as the ideal gas law....
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This note was uploaded on 04/15/2009 for the course PHYS 275 taught by Professor Harris during the Winter '09 term at Waterloo.
- Winter '09