Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9The Galactic CenterSlide 11A Black Hole at the Center of Our Galaxy?Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29ConstellationsConstellations (2)Slide 32AsterismsSlide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44The Celestial Sphere (2)Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Star trailsSlide 54Precession (1)Precession (2)The Sun and Its MotionsSlide 58The EclipticThe SeasonsSlide 61SeasonsSlide 63Slide 64Slide 65Slide 66Slide 67Slide 68Slide 69Slide 70Slide 71Slide 72Ice Age: CauseSlide 74Slide 75Slide 76Slide 77Slide 78Slide 79Slide 80Are these effects enough to explain the Ice Ages???Slide 82Slide 83Slide 84Slide 85Slide 86Slide 87Slide 88Slide 89Slide 901. Where we are in the Universe2. Motions on the sky200 billion starsMilky Way Galaxy25,000 light years,Or ~ 8 kpc1 pc = 3.26 lyGalactic year = 225 million yrOur sun is 4.6 billion yr oldThe parallax angle parcsec) in(AU1206265pdDefine 1 parsec as a distance to a star whose parallax is 1 arcsecd (in parsecs) = 1/p1 pc = 206265 AU = 3.26 lydp AU1206265arcsec) in(Small-angle formula:“Milky Way” – a milky patch of stars that rings the EarthGalactos = milk in GreekGalileo found that the Milky Way is made up of starsGalaxy M31 in Andromeda – similar to the Milky Way Galaxy1 Mpc from us~ 100 billion galaxies in the observable Universe10 day exposure photo!Over 1500 galaxies in a spot 1/30 the diameter of the MoonFarthest and oldest objects are 13 billion light years away!Hubble Deep FieldHubble Spacetelescope500 Mpc scaleWhat’s in the Center?The Galactic CenterThe Galactic CenterWide-angle optical view of the GC regionGalactic centerOur view (in visible light) towards the galactic center (GC) is heavily obscured by gas and dustExtinction by 30 magnitudes Only 1 out of 1012 optical photons makes its way from the GC towards Earth!If one looks at this region with big telescopes and near-infrared cameras one can see lots of stars. If one takes pictures every year it seems that some stars are moving very fast (up to 1500 kilometers per second). The fastest stars are in the very center - the position marked by the radio nucleus Sagittarius A* (cross). Distance between stars is less that 0.01 pcA Black Hole at the Center of Our A Black Hole at the Center of Our Galaxy?Galaxy?By following the orbits of individual stars near the center of the Milky Way, the mass of the central black hole could be determined to ~ 2.6 million solar massesRadio observations with Very Long Baseline Interferometry (VLBI) that are thousands of times more precise than optical observations (good enough to easily pin-point a source the size of a pea in New York when sitting in Paris)Size ~ 1 AU (12 Schwarzschild Radii)Density ~ 7x1021 Msun/pc3Recent VLBI observations (latest issue of Nature)Will we see a black-hole shadow soon??1 Astronomical Unit = 1.51011 mThe Kuiper Belt – home for short-period comets?? Starting in 1992, astronomers have become aware of a vast population of small bodies orbiting the sun beyond Neptune. There are at least 70,000 "trans-Neptunians" with diameters larger than 100 km in the radial zone extending outwards from the orbit of Neptune (at 30 AU) to 50 AU.1-day motion of VarunaLaunched in 1977Voyager 1 is now 95 AU from the Sun! (13 light-hours, or 14 billion km)The most distant human-made object in the UniverseSpeed 17.2 km/sec (3.6 AU per year)Voyagers 1 and 2Proxima Centauri (Alpha Centauri C)Closest star (4.2 light-years from the Sun)It would take ~ 80,000 years for Voyager 1 to reach a neighboring starPlutonium battery will be dead by 2020Mission may be shut down by 11/2005Golden recordLocal BubbleDensity ~ 0.05 atoms/cm3Temperature ~ 105 KRemnant of supernovaexplosion?107 mplanets109 mSun1017 m= 3 pcdistancebetweenstars1021 m= 10 kpcgalaxy1011 m= 1 AUSolar System1025 m= 100 MpcLargeststructure1026 m= GpcHubbleradiusDistance scaleLooking through space = travel in time!1.1.Classification of objects on the skyClassification of objects on the sky2.2.Description of motions of these objectsDescription of motions of these objects3.3.Understanding 1 and 2Understanding 1 and 2The constellations are an ancient heritage handed down for thousands of years as celebrations of great heroes and mythical creatures. Here Sagittarius and Scorpius hang above the southern horizon.ConstellationsConstellationsIn ancient times, constellations only referred to the brightest stars that appeared to form groups, representing mythological figures.Constellations (2)Constellations (2)Today, constellations are well-defined regions on the sky, irrespective of the presence or absence of bright stars in those regions.Names and Standard Abbreviations of ConstellationsThe following list of constellation names and abbreviations is in accordance with the resolutions of the International Astronomical Union (Trans. IAU, 1, 158; 4, 221; 9, 66 and 77). The boundaries of the constellations are listed by E. Delporte, on behalf of the IAU, in, Delimitation scientifique des constellations (tables et cartes), Cambridge University Press, 1930; they lie along the meridians of right ascension and paralleIs of declination for the mean equator and equinox of 1875.0. Nominative Nominative Genitive Genitive Nominative Nominative GenitiveGenitiveAndromeda Andromeda And And Andromedae Andromedae Lacerta Lacerta Lac Lac LacertaeLacertaeAntlia Antlia Ant Ant Antliae Antliae Leo Leo Leo Leo LeonisLeonisApus Apus Aps Aps Apodis Apodis Leo Minor Leo Minor LMi LMi Leonis MinorisLeonis MinorisAquarius Aquarius Aqr Aqr Aquarii Aquarii Lepus Lepus Lep Lep LeporisLeporisAquila Aquila Aql Aql Aquilae Aquilae Libra Libra Lib Lib LibraeLibraehttp://www.iau.org/IAU/Activities/nomenclature/const.htmlInternational Astronomical Union (IAU)88 constellationsAsterismsAsterismsSmall dipperSummer triangleHipparchus of Rhodes Born: 190 BC in Nicaea (now Iznik), Bithynia (now Turkey)Died: 120 BC in probably Rhodes, GreeceCatalogue of 850 starsDiscovered precession of the Earth’s orbitDetermined the distance to the moonCompiled trigonometric tablesFor thousands of years, discoveries in math and science were driven by astronomical observations!Claudius PtolemyBorn: about 85 in EgyptDied: about 165 in Alexandria, EgyptAlmagestShares with Euclid's "Elements" the glory of being the
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