The Death of Stars.ppt - The Evolution and Death of Stars...

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The Evolution and Death of Stars
Stars spend most of their life cycleson the Main SequenceMain Sequence stars are in hydrostatic equilibriumbecause nuclear fusion is turning hydrogen intohelium and producing enough outward pressure tobalance gravitational collapse.90% of all stars are found on the Main Sequence90% of the whole life of all stars is spent on theMain SequenceBUT – What happens when the hydrogen runs out?
Stars Leave the Main SequenceThe hydrogen atoms in the core of the star thatfuse together to create helium, start to run outand fusion begins to slow downThe system becomesout of balanceSomething has to happen to keep the star fromcollapsing in on itself
Out of balanceStart running out of hydrogen in the core, now theoutward pressure is less than the gravitationalcollapse
Out of balanceWhat will happen to the core?
When core hydrogen fusion ceases, amain-sequence star becomes a giantWhen hydrogen fusion ceases in the core, the starwill collapse inward – thiscauses the layer justoutside the core to become so hot and dense thathydrogen fusion will begin in this outer layer.The energy produced by hydrogen fusion in thislayer just outside the core causes the rest of thestar to expand into a giant star.Stellar burp!
Helium fusion begins at the coreof a giantWhile the exterior layers expand, the helium corecontinues to contract and eventually becomes hotenough (100 million Kelvin) for helium to beginto fuse into carbon and oxygencore helium fusion3 HeC + energyandC + HeO + energy
Main Sequence Stars become Red GiantsHelium fusionHydrogen fusion
Background image
As stars evolve,stars move frombeing mainsequence stars toRedGiantswheretheyincrease inluminosity andbrightness anddecrease intemperature
InterstellarCloud (gasand dust)MainSequenceStarRedGiantThe Life of a Star
Main Sequence Stars become Red GiantsHelium fusionHydrogen fusion

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Term
Spring
Professor
Bridenbecker,B
Tags
Supernova, White dwarf, Neutron star

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