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Fundamental Astronomy PDF

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Sixth Edition Hannu Karttunen Pekka Kröger Heikki Oja Markku Poutanen Karl Johan Donner Editors Fundamental Astronomy Hannu Karttunen (cid:2) Pekka Kröger (cid:2) Heikki Oja (cid:2) Markku Poutanen (cid:2) Karl Johan Donner Editors Fundamental Astronomy Sixth Edition With 419 Illustrations Including 34 Colour Plates and 83 Exercises with Solutions Editors HannuKarttunen MarkkuPoutanen TuorlaObservatory Dept.Geodesy&Geodynamics UniversityofTurku FinnishGeodeticInstitute Piikkiö,Finland Masala,Finland PekkaKröger KarlJohanDonner Helsinki,Finland FinnishGeodeticInstitute Helsinki,Finland HeikkiOja ObservatoryandAstrophysics Laboratory UniversityofHelsinki Helsinki,Finland ISBN978-3-662-53044-3 ISBN978-3-662-53045-0(eBook) DOI10.1007/978-3-662-53045-0 LibraryofCongressControlNumber:2016957787 SpringerHeidelbergNewYorkDordrechtLondon ©Springer-VerlagBerlinHeidelberg1987,1994,1996,2003,2007,2017 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewhole orpartofthematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseof illustrations,recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway, andtransmissionorinformationstorageandretrieval,electronicadaptation,computersoftware, orbysimilarordissimilarmethodologynowknownorhereafterdeveloped. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthis publication does not imply, even in the absence of a specific statement, that such names are exemptfromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationin thisbookarebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublisher northeauthorsortheeditorsgiveawarranty,expressorimplied,withrespecttothematerial containedhereinorforanyerrorsoromissionsthatmayhavebeenmade. Coverillustration:AtacamaLargeMillimeter/submillimeterArray(ALMA)isaninterferom- etertelescopecomposedof66antennas.ALMAobservesmoleculargasanddustofthecool Universe—building blocks of stars, planetary systems, galaxies and life itself. Credit: ESO/ Y.Beletsky Printedonacid-freepaper SpringerispartofSpringerScience+BusinessMedia(www.springer.com) Preface to the Sixth Edition As the title suggests, this book is about fundamental things that one might expecttoremainfairlythesame.Yetastronomyhasevolvedenormouslyover thelastfewyears,andonlyafewchaptersofthisbookhavebeenleftunmod- ified. Since the book is used also by many amateurs, the introductory chapter has been extended to give a brief summary of different celestial objects to “soften”thejumptorathertechnicaltopics. Thechapteronthesolarsystemwasverylong.Ithasnowbeensplitinto two separate chapters. Chapter 7 deals with general properties of the solar system. Individual objects are discussed in Chap. 8, which is more prone to change when new data will accumulate. Also, new data on exoplanets is obtained at an increasing rate. Therefore exoplanets are given a chapter of theirown;itisattheendofthebook,sinceitiscloselyrelatedtoastrobiology, alreadyincludedinthepreviousedition.Theselastchaptersmaychangemore thantherestofthebookinthefuture. These changes mean that the numbering of formulas and figures has changedquiteextensivelyafterthepreviousversionofthebook. Cosmologyandgalacticastronomyhavestillbeenevolvingrapidly.There- foretherearemanyrevisionstothechaptersontheMilkyWay,galaxies,and cosmology. In addition,several other chapters containsmaller revisions and manyof thepreviousimageshavebeenreplacedwithnewerones. Helsinki,Finland HannuKarttunen April2016 PekkaKröger HeikkiOja MarkkuPoutanen KarlJohanDonner v Preface to the First Edition Themainpurposeofthisbookistoserveasauniversitytextbookforafirst courseinastronomy.However,webelievethattheaudiencewillalsoinclude manyseriousamateurs,whooftenfindthepopulartextstootrivial.Thelack ofagoodhandbookforamateurshasbecomeaproblemlately,asmoreand morepeoplearebuyingpersonalcomputersandneedexact,butcomprehen- sible,mathematicalformalismfortheirprograms.Thereaderofthisbookis assumedtohaveonlyastandardhigh-schoolknowledgeofmathematicsand physics(astheyaretaughtinFinland);everythingmoreadvancedisusually derived step by step from simple basic principles. The mathematical back- ground needed includes plane trigonometry, basic differential and integral calculus,and(onlyinthechapterdealingwithcelestialmechanics)somevec- torcalculus.Somemathematicalconceptsthereadermaynotbefamiliarwith arebrieflyexplainedintheappendicesorcanbeunderstoodbystudyingthe numerous exercises and examples. However, most of the book can be read with very little knowledge of mathematics, and even if the reader skips the mathematicallymoreinvolvedsections,(s)heshouldgetagoodoverviewof thefieldofastronomy. Thisbookhasevolvedinthecourseofmanyyearsandthroughthework ofseveralauthorsandeditors.Thefirstversionconsistedoflecturenotesby one of the editors (Oja). These were later modified and augmented by the other editors and authors. Hannu Karttunen wrote the chapters on spherical astronomyandcelestialmechanics;VilppuPiirolaaddedpartstothechapter on observational instruments, and Göran Sandell wrote the part about radio astronomy; chapters on magnitudes, radiation mechanisms and temperature wererewrittenbytheeditors;MarkkuPoutanenwrotethechapterontheso- larsystem;JuhaniKyröläinenexpandedthechapteronstellarspectra;Timo Rahunenrewrotemostofthechaptersonstellarstructureandevolution;Ilkka Tuominen revised the chapter on the Sun; Kalevi Mattila wrote the chapter on interstellar matter; Tapio Markkanen wrote the chapters on star clusters and the Milky Way; Karl Johan Donner wrote the major part of the chap- ter on galaxies; Mauri Valtonen wrote parts of the galaxy chapter, and, in collaboration with Pekka Teerikorpi, the chapter on cosmology. Finally, the resulting, somewhat inhomogeneous, material was made consistent by the editors. The English text was written by the editors, who translated parts of the originalFinnishtext,andrewroteotherparts,updatingthetextandcorrecting vii viii PrefacetotheFirstEdition errorsfoundintheoriginaledition.Thepartsoftextsetinsmallerprintare lessimportantmaterialthatmaystillbeofinteresttothereader. For the illustrations, we received help from Veikko Sinkkonen, Mirva Vuoriandseveralobservatoriesandindividualsmentionedinthefigurecap- tions.Inthepracticalwork,wewereassistedbyArjaKyröläinenandMerja Karsma.ApartofthetranslationwasreadandcorrectedbyBrianSkiff.We wanttoexpressourwarmestthankstoallofthem. FinancialsupportwasgivenbytheFinnishMinistryofEducationandSuo- malaisenkirjallisuudenedistämisvarojenvaltuuskunta(afoundationpromot- ingFinnishliterature),towhomweexpressourgratitude. Helsinki,Finland HannuKarttunen June1987 PekkaKröger HeikkiOja MarkkuPoutanen KarlJohanDonner Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 CelestialObjects . . . . . . . . . . . . . . . . . . . . . . 1 1.2 TheRoleofAstronomy . . . . . . . . . . . . . . . . . . 3 1.3 AstronomicalObjectsofResearch . . . . . . . . . . . . . 4 1.4 TheScaleoftheUniverse . . . . . . . . . . . . . . . . . 10 2 SphericalAstronomy . . . . . . . . . . . . . . . . . . . . . . . 11 2.1 SphericalTrigonometry . . . . . . . . . . . . . . . . . . 11 2.2 TheEarth . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.3 TheCelestialSphere . . . . . . . . . . . . . . . . . . . . 16 2.4 TheHorizontalSystem . . . . . . . . . . . . . . . . . . . 16 2.5 TheEquatorialSystem . . . . . . . . . . . . . . . . . . . 17 2.6 RisingandSettingTimes . . . . . . . . . . . . . . . . . . 20 2.7 TheEclipticSystem . . . . . . . . . . . . . . . . . . . . 21 2.8 TheGalacticCoordinates. . . . . . . . . . . . . . . . . . 22 2.9 PerturbationsofCoordinates . . . . . . . . . . . . . . . . 22 2.10 PositionalAstronomy . . . . . . . . . . . . . . . . . . . 27 2.11 Constellations. . . . . . . . . . . . . . . . . . . . . . . . 31 2.12 StarCataloguesandMaps . . . . . . . . . . . . . . . . . 31 2.13 SiderealandSolarTime . . . . . . . . . . . . . . . . . . 34 2.14 AstronomicalTimeSystems . . . . . . . . . . . . . . . . 38 2.15 Calendars . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2.16 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 45 2.17 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3 ObservationsandInstruments. . . . . . . . . . . . . . . . . . 51 3.1 ObservingThroughtheAtmosphere . . . . . . . . . . . . 51 3.2 OpticalTelescopes . . . . . . . . . . . . . . . . . . . . . 54 3.3 DetectorsandInstruments . . . . . . . . . . . . . . . . . 64 3.4 RadioTelescopes . . . . . . . . . . . . . . . . . . . . . . 74 3.5 OtherWavelengthRegions . . . . . . . . . . . . . . . . . 80 3.6 OtherFormsofEnergy . . . . . . . . . . . . . . . . . . . 85 3.7 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 89 3.8 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . 90 4 PhotometricConceptsandMagnitudes . . . . . . . . . . . . . 91 4.1 Intensity,FluxDensityandLuminosity . . . . . . . . . . 91 ix x Contents 4.2 ApparentMagnitudes . . . . . . . . . . . . . . . . . . . . 93 4.3 MagnitudeSystems . . . . . . . . . . . . . . . . . . . . . 94 4.4 AbsoluteMagnitudes . . . . . . . . . . . . . . . . . . . . 96 4.5 ExtinctionandOpticalThickness . . . . . . . . . . . . . 97 4.6 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 99 4.7 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . 101 5 RadiationMechanisms . . . . . . . . . . . . . . . . . . . . . . 103 5.1 RadiationofAtomsandMolecules. . . . . . . . . . . . . 103 5.2 TheHydrogenAtom . . . . . . . . . . . . . . . . . . . . 105 5.3 LineProfiles . . . . . . . . . . . . . . . . . . . . . . . . 107 5.4 QuantumNumbers,SelectionRules,PopulationNumbers 108 5.5 MolecularSpectra . . . . . . . . . . . . . . . . . . . . . 111 5.6 ContinuousSpectra . . . . . . . . . . . . . . . . . . . . . 111 5.7 BlackbodyRadiation . . . . . . . . . . . . . . . . . . . . 111 5.8 Temperatures . . . . . . . . . . . . . . . . . . . . . . . . 114 5.9 OtherRadiationMechanisms. . . . . . . . . . . . . . . . 116 5.10 RadiativeTransfer . . . . . . . . . . . . . . . . . . . . . 117 5.11 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 118 5.12 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . 120 6 CelestialMechanics. . . . . . . . . . . . . . . . . . . . . . . . 123 6.1 EquationsofMotion . . . . . . . . . . . . . . . . . . . . 123 6.2 SolutionoftheEquationofMotion . . . . . . . . . . . . 124 6.3 EquationoftheOrbitandKepler’sFirstLaw . . . . . . . 126 6.4 OrbitalElements . . . . . . . . . . . . . . . . . . . . . . 127 6.5 Kepler’sSecondandThirdLaw . . . . . . . . . . . . . . 128 6.6 SystemsofSeveralBodies . . . . . . . . . . . . . . . . . 130 6.7 OrbitDetermination . . . . . . . . . . . . . . . . . . . . 131 6.8 PositionintheOrbit . . . . . . . . . . . . . . . . . . . . 132 6.9 EscapeVelocity . . . . . . . . . . . . . . . . . . . . . . . 133 6.10 VirialTheorem . . . . . . . . . . . . . . . . . . . . . . . 134 6.11 TheJeansLimit . . . . . . . . . . . . . . . . . . . . . . . 135 6.12 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 136 6.13 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . 140 7 TheSolarSystem . . . . . . . . . . . . . . . . . . . . . . . . . 141 7.1 ClassificationofObjects . . . . . . . . . . . . . . . . . . 141 7.2 PlanetaryConfigurations . . . . . . . . . . . . . . . . . . 143 7.3 OrbitoftheEarthandVisibilityoftheSun . . . . . . . . 145 7.4 TheOrbitoftheMoon . . . . . . . . . . . . . . . . . . . 147 7.5 EclipsesandOccultations . . . . . . . . . . . . . . . . . 149 7.6 TheStructureandSurfacesofPlanets . . . . . . . . . . . 151 7.7 AtmospheresandMagnetospheres . . . . . . . . . . . . . 154 7.8 Albedos . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 7.9 Photometry,PolarimetryandSpectroscopy . . . . . . . . 162 7.10 ThermalRadiationofthePlanets. . . . . . . . . . . . . . 166 7.11 OriginoftheSolarSystem . . . . . . . . . . . . . . . . . 167 7.12 NiceModels . . . . . . . . . . . . . . . . . . . . . . . . 174 Contents xi 7.13 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 175 7.14 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . 178 8 ObjectsoftheSolarSystem . . . . . . . . . . . . . . . . . . . 181 8.1 Mercury . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 8.2 Venus . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 8.3 TheEarthandtheMoon . . . . . . . . . . . . . . . . . . 188 8.4 Mars . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 8.5 Jupiter. . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 8.6 Saturn . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 8.7 Uranus . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 8.8 Neptune . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 8.9 DwarfPlanets . . . . . . . . . . . . . . . . . . . . . . . . 212 8.10 MinorBodies . . . . . . . . . . . . . . . . . . . . . . . . 214 8.11 Asteroids . . . . . . . . . . . . . . . . . . . . . . . . . . 214 8.12 Comets . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 8.13 Meteoroids . . . . . . . . . . . . . . . . . . . . . . . . . 222 8.14 InterplanetaryDustandOtherParticles . . . . . . . . . . 224 8.15 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 224 8.16 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . 225 9 StellarSpectra . . . . . . . . . . . . . . . . . . . . . . . . . . 227 9.1 MeasuringSpectra . . . . . . . . . . . . . . . . . . . . . 227 9.2 TheHarvardSpectralClassification . . . . . . . . . . . . 229 9.3 TheYerkesSpectralClassification . . . . . . . . . . . . . 232 9.4 PeculiarSpectra . . . . . . . . . . . . . . . . . . . . . . 234 9.5 TheHertzsprung–RussellDiagram . . . . . . . . . . . . . 235 9.6 ModelAtmospheres . . . . . . . . . . . . . . . . . . . . 236 9.7 WhatDotheObservationsTellUs? . . . . . . . . . . . . 237 9.8 Exercise . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 10 BinaryStarsandStellarMasses . . . . . . . . . . . . . . . . . 241 10.1 VisualBinaries . . . . . . . . . . . . . . . . . . . . . . . 241 10.2 AstrometricBinaryStars . . . . . . . . . . . . . . . . . . 242 10.3 SpectroscopicBinaries . . . . . . . . . . . . . . . . . . . 243 10.4 PhotometricBinaryStars . . . . . . . . . . . . . . . . . . 244 10.5 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 246 10.6 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . 247 11 StellarStructure . . . . . . . . . . . . . . . . . . . . . . . . . 249 11.1 InternalEquilibriumConditions . . . . . . . . . . . . . . 249 11.2 PhysicalStateoftheGas . . . . . . . . . . . . . . . . . . 252 11.3 StellarEnergySources . . . . . . . . . . . . . . . . . . . 254 11.4 StellarModels . . . . . . . . . . . . . . . . . . . . . . . 257 11.5 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 260 11.6 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . 262 12 StellarEvolution . . . . . . . . . . . . . . . . . . . . . . . . . 263 12.1 EvolutionaryTimeScales . . . . . . . . . . . . . . . . . 263 12.2 TheContractionofStarsTowardstheMainSequence . . . 264

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