Overview The Sky from Earth (Planetarium) How do objects ......

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  • The Sky from EarthThe Sky from Earth

    (Planetarium)(Planetarium)

    PSC 203PSC 203

    OverviewOverview

    � In this section:In this section: � What do we see from Earth?What do we see from Earth?

    � How do objects in the sky move daily?How do objects in the sky move daily?

    � How do objects in the sky move yearly?How do objects in the sky move yearly?

    � How do things change at other locations?How do things change at other locations?

    The celestial sphereThe celestial sphere

    � For objects such as the Sun and stars, we For objects such as the Sun and stars, we

    cannot directly perceive their distancecannot directly perceive their distance

    � Historically the sky was perceived as a Historically the sky was perceived as a

    sphere with little lights on itsphere with little lights on it

    � We still use the same vocabularyWe still use the same vocabulary

    The celestial sphereThe celestial sphere

    VocabularyVocabulary

    � Horizon – the horizontal circle separating Horizon – the horizontal circle separating

    the sky from the groundthe sky from the ground

    � Zenith – the point straight overheadZenith – the point straight overhead

    � Meridian – line from North to south Meridian – line from North to south

    through zeniththrough zenith

  • CoordinatesCoordinates

    � Just like the curved surface of the earth Just like the curved surface of the earth

    has a coordinate system …has a coordinate system …

    � So does the sky, 2 systems in factSo does the sky, 2 systems in fact � Altitude and AzimuthAltitude and Azimuth

    � Right Ascension and DeclinationRight Ascension and Declination

    � These will be studied in the planetariumThese will be studied in the planetarium

    Altitude and AzimuthAltitude and Azimuth

    � Altitude – how far above the horizonAltitude – how far above the horizon � 0 on horizon0 on horizon

    � 90 at zenith90 at zenith

    � Azimuth – how far around horizonAzimuth – how far around horizon � 0 at north0 at north

    � 90 at east, 180 at south, 270 at west90 at east, 180 at south, 270 at west

    Altitude and AzimuthAltitude and Azimuth Celestial coordinatesCelestial coordinates

    � Project Earth’s coordinates out into spaceProject Earth’s coordinates out into space

    � →Equator Celestial equator→Equator Celestial equator

    � →Poles Celestial poles→Poles Celestial poles

    � →Longitude Right Ascension→Longitude Right Ascension

    � →Latitude Declination→Latitude Declination

    Celestial coordinatesCelestial coordinates

  • Overview of SCOverview of SC North PoleNorth Pole

    Overview of SCOverview of SC EquatorEquator

  • Motion of the starsMotion of the stars

    Motion of the StarsMotion of the Stars

    � Depends on location, we will look at South Depends on location, we will look at South

    Carolina first (SC)Carolina first (SC)

    � Latitude ~35 NLatitude ~35 N

    SC, looking southSC, looking south

    � Stars rise SEStars rise SE

    � Have low altitude at Have low altitude at

    the meridianthe meridian

    � Set in SWSet in SW

    SC, looking eastSC, looking east

    � Stars rise along Stars rise along

    eastern horizoneastern horizon

    � Move up in at an Move up in at an

    angle towards the angle towards the

    southsouth

    SC, looking westSC, looking west

    � Move down towards Move down towards

    the western horizon the western horizon

    an angle from the an angle from the

    southsouth

    SC, looking northSC, looking north

    � Some star rise is NE Some star rise is NE

    and set in NWand set in NW

    � Others circle around Others circle around

    the north celestial the north celestial

    pole (circumpolar)pole (circumpolar)

  • Overview of SCOverview of SC Star pathsStar paths

    � The path of stars are different in different The path of stars are different in different

    locationslocations � We will look atWe will look at

    � Equator – latitude 0Equator – latitude 0

    � South Africa – latitude ~40SSouth Africa – latitude ~40S

    � Alaska – latitude ~60NAlaska – latitude ~60N

    � North Pole – latitude ~90NNorth Pole – latitude ~90N

    EquatorEquator

    � Stars move from east to west more Stars move from east to west more

    directly overhead directly overhead � (instead of arcs towards the southern horizon)(instead of arcs towards the southern horizon)

    � There are no circumpolar starsThere are no circumpolar stars

    � Celestial poles are on the horizonCelestial poles are on the horizon

    EquatorEquator

    North PoleNorth Pole

    � North celestial pole at zenith (overhead)North celestial pole at zenith (overhead)

    � Stars are all circumpolar and move around Stars are all circumpolar and move around

    at constant altitudes at constant altitudes

    North PoleNorth Pole

  • South AfricaSouth Africa

    � Star move from East to West along an arc Star move from East to West along an arc

    towards the northern horizontowards the northern horizon � (instead of towards the southern horizon)(instead of towards the southern horizon)

    � Stars in the south are circumpolar around Stars in the south are circumpolar around

    the south celestial pole the south celestial pole � (north celestial pole not visible)(north celestial pole not visible)

    AlaskaAlaska

    � Stars move in very low arcs from east to Stars move in very low arcs from east to

    west along the southern horizonwest along the southern horizon

    � Most stars in the sky are circumpolarMost stars in the sky are circumpolar

    � North celestial pole is high in sky North celestial pole is high in sky

    AlaskaAlaska

    � My figureMy figure

    Motion of the SunMotion of the Sun

    Sun motion Sun motion

    � Depends on location and seasonDepends on location and season

    � We will first look at South Carolina’s view We will first look at South Carolina’s view

    in each season…in each season…

  • SC, winterSC, winter

    � Rises in SERises in SE

    � Reaches low altitude at noon Reaches low altitude at noon

    � Sets in SWSets in SW

    � Night longer than dayNight longer than day

    SC, springSC, spring

    � Rises in ERises in E

    � Reaches mid altitude at noon Reaches mid altitude at noon

    � Sets in WSets in W

    � Day and night equalDay and night equal

    SC, summerSC, summer

    � Rises in NERises in NE

    � Reaches high altitude at noon Reaches high altitude at noon

    � Sets in NWSets in NW

    � Day longer than nightDay longer than night

    SC, fallSC, fall

    � Rises in ERises in E

    � Reaches mid altitude at noon Reaches mid altitude at noon

    � Sets in WSets in W

    � Day and night equalDay and night equal

    SCSC EquatorEquator

    � Sun always moves more overheadSun always moves more overhead

  • EquatorEquator South CarolinaSouth Carolina

    AlaskaAlaska North PoleNorth Pole

    South AfricaSouth Africa

    � My diagramMy diagram

    Ecliptic verses equatorEcliptic verses equator

    � In March, ecliptic on celestial equatorIn March, ecliptic on celestial equator

    � In June, ecliptic north of celestial equatorIn June, ecliptic north of celestial equator

    � In Sep, ecliptic on celestial equatorIn Sep, ecliptic on celestial equator

    � In Dec, ecliptic south of celestial equatorIn Dec, ecliptic south of celestial equator

  • Ecliptic verses equatorEcliptic verses equator