Lecture_Chap_12_2-21_

Lecture_Chap_12_2-21_ - Midterm 2 Next Thursday Two rooms...

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Midterm 2 Next Thursday • Two rooms for test?? • Review sheet and sample test are posted • Lecture notes for Chapter 11 are posted
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Lifeline of the Sun Possible test question: Why are most stars we see on the Main Sequence? now
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Computing a model of Stellar Evolution The results are compared with the stars that we see in the sky, and the model is adjusted accordingly.
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Gravitational Contraction and Heating • As the gas cloud of the star contracts smaller, the atoms are falling inwards, and heat the interior. • This ignites hydrogen burning at the beginning, and will continue to ignite further nuclear reactions as each fuel is used up. • Gravitational contraction will continue to a Black Hole unless a structure forms that can support the pressure without high temperature; i.e., the electron degeneracy of a white dwarf, or the neutron degeneracy of a neutron star.
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Summary of the Life of a Sun-like Star
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Evolution Off the Main Sequence
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Structure of a Red Giant Tiny compact He core, degenerate matter, super hot, size of Earth, contains ± of mass of star Hydrogen burning shell Vast distended envelope, size of Earth’s orbit, outer parts are quite rarified, cool and red, probably looks diffuse without a sharp edge
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Red Giant
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Degenerate Matter • Text calls it “dense matter”. • In core of red giant, and also makes up a white dwarf (W.D.) • The electrons are so dense that they pack up in quantum states through the whole core via the Pauli Exclusion Principle (Core or W.D. is sort of like a giant atom.) • Density = 10 9 Kg/m 3 = 5 tons/cm 3 • Can support pressure without high temperatures
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Helium Burning The Triple Alpha Reaction
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Track on the HR diagram Sub giant Red giant Helium flash Asymptotic giant (The text shows this in stages.)
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Planetary Nebulae (misnomer) Ring Eskimo Eight-Burst Cat’s Eye
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This note was uploaded on 04/23/2008 for the course ASTR 3 taught by Professor Hauser during the Winter '07 term at UCLA.

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Lecture_Chap_12_2-21_ - Midterm 2 Next Thursday Two rooms...

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