life cycle of a star. what is a star? 1. giant balls of exploding gas consisting mainly of hydrogen...
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Life Cycle of a Star
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What is a Star?
• 1. Giant balls of exploding gas consisting mainly of hydrogen and helium.
• 2. There are 100 billion stars in the Milky Way Galaxy alone
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The Life Cycle of a Star Depends on its Mass
• 1. Nebula
• 2. Star/Large Star
• 3. Red Giant/Red Supergiant
• 4. Planetary Nebula/SuperNova
• 5. White Dwarf/ Blackhole/ Neutron Star
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The Life Cycle Depends on Starting Mass Cont.
ProtostarMain SequenceWhite DwarfBlack Dwarf
ProtostarMain SequenceRed GiantWhite DwarfBlack Dwarf
ProtostarMain SequenceSuper GiantSupernova
neutron star black hole
Small Mass Medium Mass Large Mass
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I: Stage One: a Nebula
• 1. All stars begin the same way
• 2. A nebula is a cloud of interstellar dust, hydrogen & helium gas, and plasma
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II: Stage Two: The Protostar
• 1. Ball of gas and dust that is pulled together by gravity
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III: Stage Three: Main Sequence
• 1. All stars go through a Main Sequence stage
• 2. Hydrogen fuses into helium which creates enormous amounts of energy (nuclear fusion)
• 3. Stars in the main sequence stage are middle aged stars
• 4. Longest stage
• 5. Luminosity (light) depends directly on temperature
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IV: Stage Four: White Dwarf (Small Mass Star)
• 1. Small hot star that is the leftover center of an older star
• 2. Cooler & less bright than the main sequence star
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IV: Stage Four: Red Giant (Medium Mass Star)
• 1. Occurs when star begins running out of hydrogen – it starts cooling and expanding at the same time
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IV: Stage Four: Supergiant (Large Mass Star)
• 1. Occurs when star begins running out of hydrogen – it starts cooling and expanding at the same time
• 2. The only difference between a Red Giant and a Super Red Giant is the size and the luminosity
• 3. 1,000,000 times brighter than the sun
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V: Stage Five: Black Dwarf (Small Mass Star)
• 1. A Black Dwarf is a White Dwarf that has cooled so much that it no longer emits heat or light
• 2. It is estimated that it takes more than 13 billion years for this to occur, so there are no black dwarfs around
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V: Stage Five White Dwarf (Medium Mass Star)
• 1. Small hot star that is the leftover center of an older star
• 2. Cooler & less bright than the Red Giant
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V: Stage Five: Supernova (Large Mass Star)
• 1. Gigantic explosion in which a massive star collapses after it uses up all its fuel
• 2. A Supernova explosion outshines an entire galaxy. It radiates as much energy as the Sun will emit over its entire life span
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VI: Stage Six: Black Dwarf (Medium Mass Star)
• 1. A Black Dwarf is a White Dwarf that has cooled so much that it no longer emits heat or light
• 2. It is estimated that it takes more than 13 billion years for this to occur, so there are no black dwarfs around
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VI: Stage Six: Neutron Star OR Black Hole (Large Mass Star)
• 2. Black Holes exhibit so much gravitational pull, that nothing can escape (including light rays)
• 1. Neutron Star- a star that has collapsed to a point at which all particles are neutrons1