页数：43页文件大小：9.76 MB来源： 天文学概论ppt课件
本课件为《天文学概论》第一章宇宙概观的前半部分，从太阳大气的光球、色球与日冕三层讲起，依次展开太阳黑子与磁场、11年太阳活动周、日珥与空间天气，说明质子—质子链如何为太阳提供能量，并给出八大行星的参数对照与行星分类依据。
通识课天文学概论
第一章宇宙概观1.1太阳系1.2恒星世界1.3银河系及河外星系
1.1.1太阳1.1.2太阳系行星1.1.3地球1.1.4日月食1.1.5太阳系的物质分布1.1
1.1.1太阳
太阳大气（the Solar Atmosphere）Heat Flow太阳内部只有在日食期间可观测到人眼看到的太阳光球色球日冕
Apparent surface layer of the sun光球（photosphere）日冕
光球的能力传输Energy generated in the sun’s center must be transported outward.In thephotosphere, this happens through对流（Convection）Bubbles of hotgas rising upCool gassinking down≈1000 kmBubbles last for≈10–20 min.
米粒组织（Granulation）… is the visible consequence of convection
色球（Chromosphere）Chromospheric structuresvisible in Hαemission(filtergram)
针状体Spicules: Filamentsof cooler gas from thephotosphere, risingup into thechromosphere.Visible in Hαemission.Each one lastingabout 5–15 min.
太阳大气层VisiblePhotosphereUltravioletChromosphereCoronal activity,seen in visiblelightCoronaSun SpotRegions
日冕磁场
太阳风（the Solar Atmosphere）Constant flow of particles from the sun.Velocity≈ 300–800 km/s⇒Sun is constantly losing mass:107tons/year(≈ 10-14of its mass per year)
日震（Helioseismology）The solar interior is opaque (i.e.it absorbs light) out to thephotosphere.⇒Only way to investigatesolar interior is throughHelioseismology= analysis of vibration patternsvisible on thesolar surface:Approx. 10 millionwave patterns!
太阳黑子（Sun Spots）Cooler regions of thephotosphere (T≈ 4240 K).Only appear dark against the brightsun. Would still be brighter thanthe full moon when placed on thenight sky!
太阳黑子（2）Active RegionsVisibleUltraviolet
太阳表面Solar Activity, seen in soft X-rays
黑子中的磁场（Magnetic Fields in Sun Spots）Magnetic fields on the photosphere can be measuredthrough the Zeeman effect→Sun Spots are related to magnetic activityon the photosphere
太阳黑子(3)Magnetic field in sun spots is about 1000 times stronger thanaverage.In sun spots, magnetic field lines emerge out of thephotosphere.Magnetic North PolesMagneticSouthPoles
磁力线（Magnetic Field Lines）MagneticNorthPoleMagneticSouth PoleMagneticField Lines
恒星黑子（Star Spots）?Other stars might also have sun spot activity:Image constructedfrom changingDoppler shiftmeasurements
太阳周（The Solar Cycle）11-year cycleReversal of magnetic polarityAfter 11 years, North/Southorder of leading/trailing sunspots is reversed=> Total solar cycle= 22 years
太阳周(2)蒙德蝴蝶图（Maunder ButterflyDiagram）Sun spot cycle starts out with spots at higherlatitudes on the sunEvolve to lower latitudes (towards the equator)throughout the cycle.
太阳磁动力学（Magnetic Dynamo）This differential rotation might be responsible formagnetic activity of the sun.The sun rotates faster at the equator than near thepoles.
磁环（Magnetic Loops）Magnetic field lines
太阳磁活动周（Magnetic Cycle）After 11 years, the magnetic fieldpattern becomes so complex thatthe field structure is re-arranged.→New magnetic field structureis similar to the original one, butreversed!→New 11-year cycle starts withreversed magnetic-fieldorientation
蒙德极小期（The Maunder Minimum）Historical data indicate a very quiet phase of the sun,~ 1650–1700: TheMaunder MinimumThe sun spot number also fluctuateson much longer time scales:
其他恒星上的磁活动周（Magnetic Cycles on Other Stars）H and K lineemission of ionizedCalcium indicatemagnetic activityalso on other stars.
日珥（Prominences）Looped Prominences: gas ejected from the sun’sphotosphere, flowing along magnetic loopsRelatively cool gas(60,000–80,000oK)May be seen as darkfilaments against thebright background of thephotosphere
爆发的日珥(Ultravioletimages)Extreme events (solarflares) can significantlyinfluence Earth’smagnetic field structure andcause northern lights(aurora borealis).
空间天气（Space Weather）Solar AuroraSoundwavesproducedby a solarflare~ 5 minutesCoronal mass ejections
冕洞（Coronal Holes）X-ray images ofthe sun revealcoronal holes.These arise at thefoot points ofopen field linesand are the originof the solar wind.
能量产生（Energy Production）Energy generation in the sun (andall other stars):Nuclear Fusion= fusing together 2 or morelighter nuclei to produceheavier ones.Nuclear fusion canproduce energy up to theproduction ofiron;For elements heavier thaniron, energy is gained bynuclear fission.Binding energydue to strong force= on short range,strongest of the 4known forces:electromagnetic,weak,strong,gravitational
太阳内部能力产生：质子－质子链（The Proton-Proton Chain）Basic reaction:41H→4He + energy4 protons have 0.048*10-27kg (= 0.7 %) more massthan4He.⇒Energy gain =Δm*c2= 0.43*10-11Jper reaction.Need large proton speed (↔hightemperature) to overcomeCoulombbarrier(electromagnetic repulsionbetween protons).Sun needs 1038reactions, transforming5 million tonsof mass into energy every second, to resist its owngravity.T ≥ 107K =10 million0K
太阳中微子问题The Solar Neutrino ProblemThe solar interior can not beobserved directly because it ishighly opaque to radiation.Butneutrinoscan penetratehuge amounts of materialwithout being absorbed.Davis solar neutrinoexperimentEarly solar neutrino experimentsdetected a much lower flux ofneutrinos than expected (→the“solar neutrino problem”).Recent results have proven thatneutrinos change (“oscillate”)between different types (“flavors”),thus solving the solar neutrino problem.
1.1.2太阳系行星
行星大小Assume, we reduce all bodiesin the solar system so that theEarth has diameter 0.3 mm.Mercury, Venus, Earth, Mars: ~size of a grain of salt.Sun: ~ size of a small plum.Jupiter: ~ size of an apple seed.Saturn: ~ slightly smaller thanJupiter’s“apple seed”.Pluto: ~ Speck of pepper.
八大行星参数
| 行星 | 到太阳距离（天文单位） | 公转周期（天） | 轨道偏心率 | 质量（千克） | 赤道半径（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） | 已知卫星数（个） |
|---|---|---|---|---|---|---|---|---|---|
| 水星 | 0.387 | 87.97 | 0.206 | 3.3×1023 | 2.44 | 5.43 | 3.63 | 4.30 | 0 |
| 金星 | 0.723 | 324.7 | 0.007 | 4.87×1024 | 6.07 | 5.25 | 8.60 | 10.30 | 0 |
| 地球 | 1.000 | 365.256 | 0.017 | 5.976×1024 | 6.378 | 5.52 | 9.82 | 11.21 | 1 |
| 火星 | 1.524 | 686.98 | 0.093 | 6.42×1023 | 3.395 | 3.96 | 3.76 | 5.02 | 2 |
| 木星 | 5.205 | 4332.6 | 0.048 | 1.989×1027 | 71.4 | 1.33 | 25.92 | 59.5 | 18 |
| 土星 | 9.576 | 10759 | 0.055 | 5.684×1026 | 60.0 | 0.70 | 11.29 | 35.6 | 23 |
| 天王星 | 19.28 | 30685 | 0.051 | 8.686×1025 | 25.9 | 1.24 | 11.49 | 21.4 | 15 |
| 海王星 | 30.13 | 60189 | 0.006 | 1.029×1026 | 24.75 | 1.66 | 11.59 | 23.6 | 6 |
| 冥王星 | 39.87 | 90465 | 0.256 | 1.31×1022 | 1.10 | 2.34 | 0.72 | 1.26 | 1 |
注：冥王星于2006年被国际天文学联合会列为矮行星，本表沿用课件原表中的行星序列。
注：已知卫星数为课件编撰时的数据，后续观测持续更新。
行星轨道PlutoUranusSaturnJupiterMarsEarthVenusMercuryAll planets in almostcircular (elliptical)orbits around the sun,in approx. the sameplane (ecliptic).Sense of revolution:counter-clockwiseSense of rotation:counter-clockwise(with exception ofVenus, Uranus, andPluto)Orbits generallyinclined by nomore than 3.4oExceptions:Mercury (7o)Pluto (17.2o)(Distances and times reproduced to scale)
行星分类（Two Kinds of Planets）Planets of our solar system can be divided into twovery different kinds:类地行星Terrestrial (earthlike)planets: Mercury,Venus, Earth, Mars类木行星Jovian (Jupiter-like) planets:Jupiter, Saturn, Uranus, Neptune
类地行星（Terrestrial Planets）Four inner planets ofthe solar systemRelatively small in sizeand mass (Earth is thelargest and mostmassive)Rocky surfaceSurface of Venus can not be seendirectly from Earth because of itsdense cloud cover.
行星表面环形山（Craters on Planets’Surfaces）Craters (like on ourMoon’s surface)are commonthroughout the SolarSystem.Not seen onJovian planetsbecause theydon’t have asolid surface.
类木行星（The Jovian Planets）平均密度低，都有光环，大都是气体，没有固体表面
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