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astro notes4 - Last Time Fission and Fusion Thermonuclear...

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Last Time Fission and Fusion Thermonuclear Fusion as the energy Only get fusion to go if the temp is high enough Stable equilibrium of stars Thermal equilibrium Energy generated in core defined as energy out of surface Hydrostatic equilibrium Pressure from lower layer balances weight of upper layers Linked Energy generated temp of atomic motion pressure in lower layers Energy out of sureface related to density of star related to weight of upper layers Example tin can with flame underneath Flame puts energy in, enrgy comes out from hole in top Boiling pressure of water vapor or steam means atmospheric pressure Less atmospheric pressur emeans a lower boining point Seal Can- Remove from burning Heat in is zero Heat out is not zero because its cooling Hydrostatic equilibrium weight of atmosphere crushes can pressure inside drops Ball floats Weight = water pressure from below Heat water- density drop pressure from below Properties of stars What must we observe/ measure to determine properties of stars: distance brightness, luminosity, radius, mass, temperature, composition What does it use for fuel Distance Recall second lecute: parallax (section 1.7 D = 1/p D= 1/p if d comes out its in parsecs 1 parsec =3.26 light years Proxima centauri tycho brahe could measure angles higher than 2 arcmins
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could not see parallax in starts from earth limit of p that we can measure is .005- .o1 arcsec
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This note was uploaded on 12/01/2009 for the course ASTR 50800 at USC.

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astro notes4 - Last Time Fission and Fusion Thermonuclear...

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