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Unformatted text preview: Key Concepts in Stellar Evolution Hydrostatic equilibrium
P everywhere supports weight of material above it
We can approximate this as: PC % GMf/Rf Note: massive stars will have higher central pressures, and therefore
higher central T Shell burning (w/ inert core)
Core contracts —> g at surface increases (since gshell—base = GMc/Rg ) Stellar material weighs more —> P must increase (HSE) —> increase in T
—> reaction rates increase (reactions very T sensitive) Ash from shell dumps onto core —> core mass increases —> core radius
decreases (degenerate) —> shell becomes even more luminous AST 203 (Spring 2010) Key Concepts in Stellar Evolution Fusing heavy elements requires higher T Heavy elements have more protons —> Coulomb repulsion higher
(Z1€)(Z2€) r[a2 F electric — Higher T —> higher velocity —> able to overcome Coulomb barrier (w/
tunneHng) Degenerate cores Degeneracy pressure important a high density
Greater mass core —> smaller radius —> higher g at surface AST 203 (Spring 2010) ...
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This note was uploaded on 05/04/2011 for the course AST 203 taught by Professor Simon,m during the Spring '08 term at SUNY Stony Brook.
- Spring '08