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TheFutureoftheSun(Note:notintextbook)
TheSunfuseshydrogenintoheliuminastablereaction.ButwhathappenswhentheSunrunsoutofhydrogeninitscore?
Thetimescaleforthisisabout10billionyears;weareabouthalfwaythere.
WhentheSunrunsoutofenergy,itsstructurehas tochange:stellarevolution.
TheFutureoftheSun(Note:notintextbook)
• NuclearfusionofHydrogenè HeliumprovidestheenergythathelpssupporttheSunagainstgravitationalcontraction.Withoutthat,theinnerregionswillcontractandheatup.
• Whenthathappens,thehydrogenjustoutsidethecorewillgethotenoughtostartfusingintoheliumevenmorequicklythanthecoredid:excessenergy.
• TheSunbrightensandtheouterregionsexpandandcool.TheSunbecomesaredgiant.
TheFutureoftheSun(Note:notintextbook)
EventuallythetemperatureofthecontractingHeliumcoregetssohighthatHeliumcanstartfusingintoCarbonandOxygenandreleaseenergy.TheSunsettlesdownforashorttime,muchbrighterthanbeforebutrelativelystable.
TheFutureoftheSun(Note:notintextbook)
• Only~100millionyearsafterstartingtoburnHelium,theSunwilluseupalltheHeliuminitscoreandhaveturneditintoCarbonandOxygen.Whatthen?
• SamethingthathappenedtomaketheSunaredgiant,exceptwithHeliumburninginashellaroundtheCarbon/Oxygencore.TheSunswellsevenmoreandbecomesaredsupergiant.
• Atthispoint,theSunisunstable,andtheenergyreleasedcomesinburstswhichcanactuallypushawaytheSun’s.outerlayers.
TheFutureoftheSun(Note:notintextbook)
• TheouterlayersoftheSunwillbepushedoutintospace,leavingbehindthesmallCarbon/Oxygencore.
• Theheatfromthiscorecausestheexpandingouterlayerstoshine,makingaplanetarynebula.
• Planetarynebulahavenothingtodowithplanets!
TheFutureoftheSun(Note:notintextbook)
• Aftertheouterlayersdriftawayandstopshining,allthatisleftbehindisthecoolingcoreofcarbonandoxygen,calledawhitedwarf.
• Itshinesfaintlybecauseitishot,butitsnothotenoughtodrivenuclearreactionsinvolvingcarbonoroxygen.
• Itisextremelydense,withamass abouthalfthatoftheSunandasizenotmuchlargerthantheEarth.
• Overbillionsofyears,thewhitedwarfsimplycoolsoffandfadesout.