life cycle of stars
TRANSCRIPT
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26.2
3/27/07
Star Stuff
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Forming a StarNebulacloud of dust and gas
protostar(takes 50 million years)
Contracts and rotates to form a ________
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A Star is Born!
•A star when ______ startsfusion
10
• Hydrogen atoms combine to form Helium, other atoms• Takes ___ billion years to form
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Adult Stars•Called “main sequence” stars•Longest period in life cycle•How long depends on star mass
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A Balancing Act• Two forces act on
stars•Outward force from energy released by nuclear fusion
•Inward force from gravity
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Old Age• Hydrogen fusion
slows• Gravity contracts
core• Core temperature
rises• Helium fusion
starts, releasing even more energy
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Small Stars
•Mass of our sun•Fusion forms Helium, some Lithium, Carbon and Oxygen
•Last up to ___ billion years10
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Small Star Old Age Red Giant
• Helium fusion when H atoms used up– produces heavier atoms – carbon &
oxygen
• Temperature rises with Helium fusion• Outer layers expand• Lasts ____ million years100
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Small Star Death
•Hydrogen & Helium used up
white dwarf
planetary nebula
• Outer layers expand to form a ________ _______• Star core cools and contracts to form a dim _____ _____
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Large Stars•6 x mass of our sun, or more•Fusion forms Helium, some Lithium, Carbon, Oxygen and Iron
•Last up to ___ million years10
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Old Massive Star SUPERGIANT!
•Can be 100 x larger than our sun
•Hydrogen used up•He fusion in core produces
heavier atoms•Finally, core made of Iron
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Dying Large Stars•Hydrogen gone - fusion stops•Core collapses, then rebounds
with explosion•SUPERNOVA!•Lasts few seconds
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After Supernova…
•If mass 1-3 x the sun, final stage is _______ ____neutron star
pulsar
dense
• Protons and electrons collapse together to form ________ neutrons• Very ______
• Called ______ if rotating
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After Supernova 2…
•If mass > 3 x sun, final stage is _____ ____black hole
gravitydense
• Extreme ______• Very ______
• No light escapes from it