Term
STAGE 1
Giant Molecular Cloud
(3) |
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Definition
-fragments into solar mass-size clumps
-those cores have spatial sizes .01 parsecs
-2x10^6 yrs |
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Term
STAGE 2
First Dynamical Collapse
(5) |
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Definition
-core collapses in free fall in 30,000 yrs
-cooled by IR radiation; keeps T & P low
-collapse stops when core becomes optically thick to IR
-IR Traps heat, raises pressure
-Radius: 100AU
-3x10^4yrs |
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Term
STAGE 3
Second Dynamical Collapse
(5) |
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Definition
-dissociation of molecular H & ionization of H absorbs E
-internal pressure reduces causing 2nd rapid collapse
-R=100Ro., Tcore: 500,000K, Tsurface: 4000K
-becomes protostar and shrinks
-10^5yrs |
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Term
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Definition
-interior is cool, opacity is high
-heat transported by convection
-L decreases as R decreases (10^6 yrs)
-Tsurf increases|H- decreases|opacity decreases|heat escapes more easily|Ts decreases
-Ts decreases|opacity increases|escape of heat becomes harder|Ts increases
-L decreases as protostar contracts under gravity |
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Term
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Definition
-10 Ro., 10Lo., Tc:10^6K
-deuterium burns to He3, little E
-10^7 years |
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Term
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Definition
-ends when core becomes radiative
-Tc and Ts increase
-nuclear reactions start when Tc 10&7K
-10^7 yrs |
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Term
STAGE 7
Zero Age Main Sequence
(5) |
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Definition
-energy from nuclear burning balances energy lost by rad
-star no longer needs to contract bc of energy source
-Tc 1.5x10^7K
-chemical comp doesn't change
-star to ZAMS 3x10^7yrs |
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Term
STAGE 8
Subgiant Branch
(3) |
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Definition
-3Ro.,
-happens after H is depleted & core H burning stops
-shell burning causes expansion to stellar envelope |
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Term
STAGE 9
Red Giant Branch
(3) |
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Definition
-intense H shell burning
-expansion & cooling of outer envelope
-R increases, T cools & becomes RG |
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Term
STAGE 10
Horizontal Branch |
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Definition
-stars reach hydroEqu
-star burns He in its core |
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