Introduction To Modern Astronomy I: Solar SystemHighlightsAstronomy Picture of the Day (2007/08/27)Today’s Sun (2007/08/27)Scientific MethodsExampleFormation of Solar SystemEvolution of StarsOrigin and Fate of the universeAngular MeasureAngular MeasureAngular MeasureAngular MeasureAngular MeasurePowers-of-ten notationPowers-of-ten notationUnits of Astronomical Distances Final Notes on Chap. 1Advanced Question Chap. 1, Q37 in P18ASTR 111 – 003 Fall 2007Lecture 01 Aug. 27, 2007Introducing Astronomy (chap. 1-6)Introduction To Modern Astronomy I:Introduction To Modern Astronomy I:Solar SystemSolar SystemCh1: Astronomy and the UniverseCh2: Knowing the HeavensCh3: Eclipses and the Motion of the MoonCh4: Gravitation andthe Waltz of the PlanetsCh5: The Nature of LightCh6: Optics and TelescopePlanets and Moons (chap. 7-15)Chap. 16: Our SunChap. 28: Search forExtraterrestrial lifeHighlightsHighlightsA total lunar eclipse Tuesday morning, Aug. 28, 2007A total lunar eclipse Tuesday morning, Aug. 28, 2007EDT PDTEDT PDT––Partial eclipse begins: 4:51 AM 1:51 AMPartial eclipse begins: 4:51 AM 1:51 AM––Total eclipse begins: 5:52 AM 2:52 AMTotal eclipse begins: 5:52 AM 2:52 AM––Total eclipse ends: Total eclipse ends: ----------4:23 AM4:23 AM––Partial eclipse end: Partial eclipse end: ----------5:24 AM5:24 AMGoogle Earth Google Earth ““searchessearches””the sky.the sky.Astronomy Picture of the Day (Astronomy Picture of the Day (2007/08/27)2007/08/27)Huge Void in Distant UniverseHuge Void in Distant UniverseTodayToday’’s Sun (s Sun (2007/08/27)2007/08/27)Astronomy and the UniverseAstronomy and the UniverseChapter OneChapter OneScientific MethodsScientific MethodsScientific MethodScientific Method––based on observation, logic, and skepticismbased on observation, logic, and skepticismHypothesisHypothesis––a collection of ideas that seems to explain a a collection of ideas that seems to explain a phenomenonphenomenonModelModel––hypotheses that have withstood observational or hypotheses that have withstood observational or experimental testsexperimental testsTheoryTheory––a body of related hypotheses can be pieced together a body of related hypotheses can be pieced together into a self consistent description of natureinto a self consistent description of natureLaws of PhysicsLaws of Physics––theories that accurately describe the workings of theories that accurately describe the workings of physical reality, have stood the test of time and been physical reality, have stood the test of time and been shown to have great and general validityshown to have great and general validityExampleExampleTheory: Earth and planets orbit the Sun due to the SunTheory: Earth and planets orbit the Sun due to the Sun’’s s gravitational attractiongravitational attractionFFormation of ormation of SSolar olar SSystemystem––By exploring the planets, astronomers uncover clues By exploring the planets, astronomers uncover clues about the formation of the solar systemabout the formation of the solar systemTerrestrial and Terrestrial and JovianJovianPlanetsPlanetsMeteorites. 4.56 billion yearsMeteorites. 4.56 billion yearsSolar nebulaSolar nebulaThe Sun and Planets to ScaleThe Sun and Planets to ScaleEvolution of StarsEvolution of StarsOrion NebulaOrion NebulaOur SunOur SunCrab NebulaCrab NebulaThermonuclearThermonuclearreaction; Hreaction; H--bombbombA star has a full life cycle: be born, A star has a full life cycle: be born, evolve, and dieevolve, and dieOOrigin and Fate of the universerigin and Fate of the universe––Galaxies are flying away from each otherGalaxies are flying away from each other––Expanding universeExpanding universe––Big bang theoryBig bang theoryAAngngular Measureular MeasureDenote position and size of astronomical objectDenote position and size of astronomical objectdegree (degree (°°)): t: the basic unit of angular measure he basic unit of angular measure ––One entire cycle is 360One entire cycle is 360°°AAngular diameterngular diameter, , or or angular sizeangular size––ThThe Moon is e Moon is ½½°°, and also the angular size of the Sun, and also the angular size of the SunAAngular distancengular distance::If you draw lines from your eye to each If you draw lines from your eye to each of two stars, the angle between these lines is the of two stars, the angle between these lines is the angular angular distancedistance..AAngngular Measureular MeasureThe adult human hand held at armThe adult human hand held at arm’’s length provides a s length provides a means of estimating anglesmeans of estimating angles––About 10About 10°°for the fistfor the fist––About 1About 1°°for the fingerfor the fingerAAngngular Measureular MeasureAngular MeasureAngular MeasureSubdivide one degree into 60 Subdivide one degree into 60 arcminutesarcminutes––minutes of arcminutes of arc––abbreviated as 60 abbreviated as 60 arcminarcminor 60or 60´´Subdivide one Subdivide one arcminutearcminuteinto 60 into 60 arcsecondsarcseconds––seconds of arcseconds of arc––abbreviated as 60 abbreviated as 60 arcsecarcsecor 60or 60””11°°= 60 = 60 arcminarcmin= 60= 60´´11´´= 60 = 60 arcsecarcsec= 60= 60””For exampleFor example––Moon: Moon: 0.50.5°°, 30 , 30 arcminarcmin, or , or 1800 1800 arcsecarcsec––Saturn: 20 Saturn: 20 arcsecarcsec––A star: much less than 1 A star: much less than 1 arcsecarcsec, can not be resolved by , can not be resolved by any telescopesany telescopesAngular MeasureAngular MeasureSmall angle formulaSmall angle formula––D: linear size of an objectD: linear size of an object––d: distance to the objectd: distance to the object––αα: angular size of the object,: angular size of the object,in in arcsecarcsecD = D = ααd /206265d /206265If same linear size, the more distant the object, the If same linear size, the more distant the object, the smaller the angular sizesmaller the angular sizeIf same angular size, the more distant the object, the If same angular size, the more distant the object, the greater its actual (linear) sizegreater its actual (linear) sizePowersPowers--ofof--ten notationten notationPowersPowers--ofof--ten notationten