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Unformatted text preview: Stellar structure Mass and Length scales Our local viewpoint appearance of sky and Fnding *’s, planets, galaxies changing sky & seasons phases, eclipses & tides SUN – Visible light Stars ? What is the structure nature of material How does it shine ? How does it evolve ? Know more about interior of sun than the earth !! • Equilibrium vs non-Equil. dynamic equil. (eg. orbital motion. static body) vs exploding,collapse thermal equil. and energy balance equil. of matter and radiation used very often in astrophysics to deduce state of objects e.g. stellar structure , temp. of planets gravity Gas pressure Hydrostatic equilibrium : gradient in gravitational force = gradient in press. force ¡ grav =GmM R /R 2 P gas =nkT as R increases, n,T decrease, P decreases As R increases, M R (enclosed mass) increases, ¡ grav increases radiation energy source Thermal equilibrium : energy radiated at surface must be replaced by energy energy from interior Energy sources: thermal chemical gravitational … • vast scales and regimes earth - sun = 1.5x10 13 cm , 93x10 6 miles = 1 Astronomical Unit , 1AU speed of light , c = 3x10 10 cm/s => earth-sun 500 light sec , 8 lmin pluto-sun : 40 AU, 320 lmin, 5 lhr nearest star (Proxima Centauri) : 3 lyr (0.9 parsec) sun - galactic center : 8 kpc , 24000 lyr How determined ? How determined ?...
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- Winter '09
- galactic center