class21a - Friday, Oct. 17 Syllabus, class notes, and...

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Friday, Oct. 17 Syllabus, class notes, and homeworks are at: www.as.utexas.edu courses AST 301, Lacy Reading for next week: chapter 10 The Wednesday help session is in GRG 424 at 5:00 (for the entire semester).
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Topics for this week Describe how the luminosities of main sequence stars are related to their masses. Describe the process of formation of a protostar from a molecular cloud. Describe the concept of hydrostatic equilibrium. Describe the concept of thermal equilibrium. Describe how a star changes if it is not in thermal equilibrium, and how this causes protostars to become main sequence stars and keeps the Sun’s luminosity stable. Describe how the mass-luminosity relation can be used to calculate the lifetimes of main sequence stars.
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Gas Properties Simulation Go to Phet.colorado.edu, run gas properties simulation. Put some atoms in the box. Describe what they do. Read the pressure. Turn up the heat to double the temperature. How do the atom motions change? How does the pressure change? Why? Turn the temperature back down and double the number of atoms in the box. Use light atoms this time. How do the light atoms’ motions differ? How does the pressure change? Turn off collisions. Does anything change? Hold the temperature constant and turn on gravity. How does the distribution of atoms in the box change? What else can you play with in the simulation?
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Equilibrium in stars Main-sequence stars are in equilibrium in two ways: Hydrostatic equilibrium means that the pressure of the gas inside of a star (which tries to make it expand) balances
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This note was uploaded on 07/13/2010 for the course AST 301 taught by Professor Harvey during the Fall '07 term at University of Texas at Austin.

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class21a - Friday, Oct. 17 Syllabus, class notes, and...

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