天文学英文版PPT资料 (15)

UniverseEighthEditionRogerA.Freedman•WilliamJ.KaufmannIIICHAPTER16OurStar,theSunStarsindifferentstagesoftheirevolutionmaygenerateenergyusingdifferentnuclearreactions.Thesereactionscanoccurinthecoreorinalayeraroundthecore.Atthepresent,theenergyoftheSunisgeneratedA.initscentralcorebyfissionofheavynuclei.B.fromgravitationalenergyastheSunslowlyshrinks.C.initscorebyradioactivedecayofuranium.D.inthecentralcorebyfusionofheliumnucleiandinanoutershellbyfusionofhydrogennuclei.E.initscentralcorebyfusionofhydrogennuclei.Q16.1Starsindifferentstagesoftheirevolutionmaygenerateenergyusingdifferentnuclearreactions.Thesereactionscanoccurinthecoreorinalayeraroundthecore.Atthepresent,theenergyoftheSunisgeneratedA.initscentralcorebyfissionofheavynuclei.B.fromgravitationalenergyastheSunslowlyshrinks.C.initscorebyradioactivedecayofuranium.D.inthecentralcorebyfusionofheliumnucleiandinanoutershellbyfusionofhydrogennuclei.E.initscentralcorebyfusionofhydrogennuclei.A16.1ThesurfacelayersoftheSunareverymassive.WhatstopstheSunfromcollapsingunderitsownweight?A.Thestrongnuclearrepulsionbetweentheatomsoftheselayers.B.Neutrinosexertastrongoutwardpressure,holdingthelayersup.C.Themagneticfieldexertsastrongforce.D.Thepressureoftheveryhigh-temperaturegaswithintheSunsupportstheouterlayers.E.TheinterioroftheSunisundersuchhighpressurethatitissolid.Q16.7ThesurfacelayersoftheSunareverymassive.WhatstopstheSunfromcollapsingunderitsownweight?A.Thestrongnuclearrepulsionbetweentheatomsoftheselayers.B.Neutrinosexertastrongoutwardpressure,holdingthelayersup.C.Themagneticfieldexertsastrongforce.D.Thepressureoftheveryhigh-temperaturegaswithintheSunsupportstheouterlayers.E.TheinterioroftheSunisundersuchhighpressurethatitissolid.A16.7Thisphotoshowssolargranulation.ThedarkerareasareregionswherethegasisA.hotter.B.cooler.C.Dopplershifted.D.movinglaterally.E.lessdense.Q16.9Thisphotoshowssolargranulation.ThedarkerareasareregionswherethegasisA.hotter.B.cooler.C.Dopplershifted.D.movinglaterally.E.lessdense.A16.9ThedarkregionsonthisphotooftheSunareA.thecorona.B.solargranules.C.Zeemaneffects.D.sunspots.E.prominences.Q16.11ThedarkregionsonthisphotooftheSunareA.thecorona.B.solargranules.C.Zeemaneffects.D.sunspots.E.prominences.A16.11Starsindifferentstagesoftheirevolutionmaygenerateenergyusingdifferentnuclearreactions.Thesereactionscanoccurinthecoreorinalayeraroundthecore.Atthepresent,theenergyoftheSunisgeneratedA.initscentralcorebyfissionofheavynuclei.B.fromgravitationalenergyastheSunslowlyshrinks.C.initscorebyradioactivedecayofuranium.D.inthecentralcorebyfusionofheliumnucleiandinanoutershellbyfusionofhydrogennuclei.E.initscentralcorebyfusionofhydrogennuclei.A16.1The“fuel”oftheSunis______,andthemainproductsofthenuclearreactionsinclude______.A.hydrogen/helium,neutrinos,andgammaraysB.helium/onlyneutrinosandgammaraysC.hydrogen/neutrinosandmicrowavesD.helium/neutrinosandmicrowavesE.hydrogen/onlyneutrinos.Q16.2KeyIdeasHydrogenFusionintheSun’sCore:TheSun’senergyisproducedbyhydrogenfusion,asequenceofthermonuclearreactionsinwhichfourhydrogennucleicombinetoproduceasingleheliumnucleus.TheenergyreleasedinanuclearreactioncorrespondstoaslightreductionofmassaccordingtoEinstein’sequationE=mc2.Thermonuclearfusionoccursonlyatveryhightemperatures;forexample,hydrogenfusionoccursonlyattemperaturesinexcessofabout107K.IntheSun,fusionoccursonlyinthedense,hotcore.KeyIdeasModelsoftheSun’sInterior:Atheoreticaldescriptionofastar’sinteriorcanbecalculatedusingthelawsofphysics.ThestandardmodeloftheSunsuggeststhathydrogenfusiontakesplaceinacoreextendingfromtheSun’scentertoabout0.25solarradius.Thecoreissurroundedbyaradiativezoneextendingtoabout0.71solarradius.Inthiszone,energytravelsoutwardthroughradiativediffusion.Theradiativezoneissurroundedbyaratheropaqueconvectivezoneofgasatrelativelylowtemperatureandpressure.Inthiszone,energytravelsoutwardprimarilythroughconvection.KeyIdeasSolarNeutrinosandHelioseismology:Conditionsinthesolarinteriorcanbeinferredfrommeasurementsofsolarneutrinosandofsolarvibrations.NeutrinosemittedinthermonuclearreactionsintheSun’scorehavebeendetected,butinsmallernumbersthanexpected.Recentneutrinoexperimentsexplainwhythisisso.HelioseismologyisthestudyofhowtheSunvibrates.Thesevibrationshavebeenusedtoinferpressures,densities,chemicalcompositions,androtationrateswithintheSun.KeyIdeasTheSun’sAtmosphere:TheSun’satmospherehasthreemainlayers:thephotosphere,thechromosphere,andthecorona.Everythingbelowthesolaratmosphereiscalledthesolarinterior.ThevisiblesurfaceoftheSun,thephotosphere,isthelowestlayerinthesolaratmosphere.Itsspectrumissimilartothatofablackbodyatatemperatureof5800K.Convectioninthephotosphereproducesgranules.KeyIdeasAbovethephotosphereisalayeroflessdensebuthighertemperaturegasescalledthechromosphere.Spiculesextendupwardfromthephotosphereintothechromospherealongtheboundariesofsupergranules.Theoutermostlayerofthesolaratmosphere,thecorona,ismadeofveryhigh-temperaturegasesatextremelylowdensity.Activityinthecoronaincludescoronalmassejectionsandcoronalholes.Thesolarcor