天文學(xué)概論多篇

通識(shí)課天文學(xué)概論教師：馬1麗第一章宇宙概觀

1.1太陽系1.2恒星世界1.3銀河系及河外星系

1.1.1太陽1.1.2太陽系行星1.1.3地球1.1.4日月食1.1.5太陽系的物質(zhì)分布1.11.1.1太陽太陽大氣（theSolarAtmosphere）HeatFlow太陽內(nèi)部只有在日食期間可觀測到人眼看到的太陽光球色球日冕Apparentsurfacelayerofthesun光球（photosphere）日冕Depth≈500kmTemperature≈5800oKHighlyopaque(H-ions)Absorbsandre-emitsradiationproducedinthesolarinterior光球的能力傳輸Energygeneratedinthesun’scentermustbetransportedoutward.Inthephotosphere,thishappensthrough對(duì)流（Convection）BubblesofhotgasrisingupCoolgassinkingdown≈1000kmBubbleslastfor≈10–20min.米粒組織（Granulation）…isthevisibleconsequenceofconvection色球（Chromosphere）ChromosphericstructuresvisibleinHaemission(filtergram)Regionofsun’satmospherejustabovethephotosphere.Visible,UV,andX-raylinesfromhighlyionizedgasesTemperatureincreasesgraduallyfrom≈4500oKto≈10,000oK,thenjumpsto≈1millionoKTransitionregionFilaments針狀體Spicules:Filamentsofcoolergasfromthephotosphere,risingupintothechromosphere.VisibleinHaemission.Eachonelastingabout5–15min.太陽大氣層VisiblePhotosphereUltravioletChromosphereCoronalactivity,seeninvisiblelightCoronaSunSpotRegions日冕磁場Coronacontainsverylow-density,veryhot(1millionoK)gasCoronalgasisheatedthroughmotionsofmagneticfieldsanchoredinthephotospherebelow(“magneticcarpet”)Computermodelofthemagneticcarpet太陽風(fēng)（theSolarAtmosphere）Constantflowofparticlesfromthesun.Velocity≈300–800km/sSunisconstantlylosingmass:107tons/year(≈10-14ofitsmassperyear)日震（Helioseismology）Thesolarinteriorisopaque(i.e.itabsorbslight)outtothephotosphere.

OnlywaytoinvestigatesolarinterioristhroughHelioseismology

=analysisofvibrationpatternsvisibleonthe

solarsurface:Approx.10millionwavepatterns!太陽黑子（SunSpots）Coolerregionsofthephotosphere(T≈4240K).Onlyappeardarkagainstthebrightsun.Wouldstillbebrighterthanthefullmoonwhenplacedonthenightsky!太陽黑子（2）ActiveRegionsVisibleUltraviolet太陽表面SolarActivity,seeninsoftX-rays黑子中的磁場

（MagneticFieldsinSunSpots）MagneticfieldsonthephotospherecanbemeasuredthroughtheZeemaneffect

SunSpotsarerelatedtomagneticactivityonthephotosphere太陽黑子(3)Magneticfieldinsunspotsisabout1000timesstrongerthanaverage.Insunspots,magneticfieldlinesemergeoutofthephotosphere.MagneticNorthPolesMagneticSouthPoles磁力線（MagneticFieldLines）MagneticNorthPoleMagneticSouthPoleMagneticFieldLines恒星黑子（StarSpots）?Otherstarsmightalsohavesunspotactivity:ImageconstructedfromchangingDopplershiftmeasurements太陽周（TheSolarCycle）11-yearcycleReversalofmagneticpolarityAfter11years,North/Southorderofleading/trailingsunspotsisreversed=>Totalsolarcycle

=22years太陽周(2)蒙德蝴蝶圖（MaunderButterflyDiagram）SunspotcyclestartsoutwithspotsathigherlatitudesonthesunEvolvetolowerlatitudes(towardstheequator)throughoutthecycle.太陽磁動(dòng)力學(xué)（MagneticDynamo）Thisdifferentialrotationmightberesponsibleformagneticactivityofthesun.Thesunrotatesfasterattheequatorthannearthepoles.磁環(huán)（MagneticLoops）Magneticfieldlines太陽磁活動(dòng)周（MagneticCycle）After11years,themagneticfieldpatternbecomessocomplexthatthefieldstructureisre-arranged.

Newmagneticfieldstructureissimilartotheoriginalone,butreversed!

New11-yearcyclestartswithreversedmagnetic-fieldorientation蒙德極小期（TheMaunderMinimum）Historicaldataindicateaveryquietphaseofthesun,~1650–1700:TheMaunderMinimumThesunspotnumberalsofluctuates

onmuchlongertimescales:其他恒星上的磁活動(dòng)周

（MagneticCyclesonOtherStars）HandKlineemissionofionizedCalciumindicatemagneticactivityalsoonotherstars.日珥（Prominences）LoopedProminences:gasejectedfromthesun’sphotosphere,flowingalongmagneticloopsRelativelycoolgas(60,000–80,000oK)Maybeseenasdarkfilamentsagainstthebrightbackgroundofthephotosphere爆發(fā)的日珥(Ultravioletimages)Extremeevents(solarflares)cansignificantlyinfluenceEarth’smagneticfieldstructureandcausenorthernlights(auroraborealis).空間天氣（SpaceWeather）SolarAuroraSoundwavesproducedbyasolarflare~5minutesCoronalmassejections冕洞（CoronalHoles）X-rayimagesofthesunrevealcoronalholes.Theseariseatthefootpointsofopenfieldlinesandaretheoriginofthesolarwind.能量產(chǎn)生（EnergyProduction）Energygenerationinthesun(andallotherstars):NuclearFusion=fusingtogether2ormorelighternucleitoproduceheavierones.Nuclearfusioncanproduceenergyuptotheproductionofiron;Forelementsheavierthaniron,energyisgainedbynuclearfission.Bindingenergy

duetostrongforce

=onshortrange,strongestofthe4knownforces:

electromagnetic,weak,

strong,

gravitational太陽內(nèi)部能力產(chǎn)生：質(zhì)子－質(zhì)子鏈

（TheProton-ProtonChain）Basicreaction:41H

4He+energy4protonshave0.048*10-27kg(=0.7%)moremassthan4He.Energygain=Dm*c2

=0.43*10-11Jperreaction.Needlargeprotonspeed(hightemperature)toovercomeCoulombbarrier(electromagneticrepulsionbetweenprotons).Sunneeds1038reactions,transforming5milliontonsofmassintoenergyeverysecond,toresistitsowngravity.T≥107

0K=10million0K太陽中微子問題

TheSolarNeutrinoProblemThesolarinteriorcannotbeobserveddirectlybecauseitishighlyopaquetoradiation.Butneutrinoscanpenetratehugeamountsofmaterialwithoutbeingabsorbed.DavissolarneutrinoexperimentEarlysolarneutrinoexperimentsdetectedamuchlowerfluxofneutrinosthanexpected(

the“solarneutrinoproblem”).Recentresultshaveproventhatneutrinoschange(“oscillate”)betweendifferenttypes(“flavors”),thussolvingthesolarneutrinoproblem.1.1.2太陽系行星行星大小Assume,wereduceallbodiesinthesolarsystemsothattheEarthhasdiameter0.3mm.Mercury,Venus,Earth,Mars:~sizeofagrainofsalt.Sun:~sizeofasmallplum.Jupiter:~sizeofanappleseed.Saturn:~slightlysmallerthanJupiter’s“appleseed”.Pluto:~Speckofpepper.八大行星參數(shù)

行星到太陽距離（天文單位）公轉(zhuǎn)周期（天）

軌道偏心率

質(zhì)量（千克）赤道半徑（103千米）平均密度（103千克/米3）表面重力加速度（米/秒2）逃逸速度（米/秒）已知衛(wèi)星數(shù)（個(gè)）水星0.38787.970.2063.3×10232.445.433.634.30金星0.723324.70.0074.87×10246.075.258.6010.30地球1.000365.2560.0175.976×10246.3785.529.8211.21火星1.524686.980.0936.42×10233.3953.963.765.02木星5.2054332.60.0481.989×102771.41.3325.9259.518土星9.576107590.0555.684×102660.00.7011.2935.623天王星19.28306850.0518.686×102525.91.2411.4921.415海王星30.13601890.0061.029×102624.751.6611.5923.66冥王星39.87904650.2561.31×10221.102.340.721.261行星軌道PlutoNeptuneUranusSaturnJupiterMarsEarthVenusMercuryAllplanetsinalmostcircular(elliptical)orbitsaroundthesun,inapprox.thesameplane(ecliptic).Senseofrevolution:counter-clockwiseSenseofrotation:counter-clockwise(withexceptionofVenus,Uranus,andPluto)Orbitsgenerallyinclinedbynomore