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lowmassstars.pdf - The Evolution of Low-mass Stars Stellar...

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The Evolution of Low-mass Stars
After birth, newbornstarsare very large, so they arevery bright.Gravity causesthem to contract,and theybecome fainterbecause oftheir smaller sizes.After contractingfor millionsof years, stars eventuallybecome hot enoughto fusehydrogen,whichhalts theircontraction.Theynowmaintaina stable size andluminosity untiltheyrun outof hydrogen fuel.Thisis themain sequence.Stellar Birth and Reaching the Main Sequencecontracting
All stars spend most of their liveson the main sequence, but thelengthof time on the main sequence (i.e., the time spent fusinghydrogen)dependsa lot on a star’smass.The Main SequenceLifetimes of StarsA star with a higher mass has a core with:highergravityhigherpressurehighertemperaturefuses hydrogen fasterAlthoughmore massive stars have more hydrogenfuel,theyconsumethat fuel at a much higher rate than less massive stars.As a result, more massive stars exhaust their fuel much fasterand have shorter main sequence lifetimes. The lifetimes for themost massive stars are onlya fewmillionyears while the leastmassive stars fuse hydrogenfortrillionsof years. A star with themass of the Sun fuses hydrogen for10 billionyears.
The Main SequenceLifetimes of StarsSunfew millionyears>1 trillionyears10 billion years
The Main SequenceLifetimes of Stars
After a star exhausts itshydrogen fuel,its fate isdeterminedby its mass atbirth.

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Term
Spring
Professor
Brandt
Tags
Astronomy, Stellar Evolution, Supernova, White dwarf

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