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The Sky from EarthThe Sky from Earth
(Planetarium) (Planetarium)
PSC 203 PSC 203
Overview Overview
(^) 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 sphere The celestial sphere
(^) For objects such as the Sun and stars, weFor objects such as the Sun and stars, we cannot directly perceive their distance cannot directly perceive their distance (^) Historically the sky was perceived as aHistorically the sky was perceived as a sphere with little lights on it sphere with little lights on it (^) We still use the same vocabularyWe still use the same vocabulary
The celestial sphere The celestial sphere
VocabularyVocabulary
(^) Horizon – the horizontal circle separatingHorizon – the horizontal circle separating the sky from the ground the sky from the ground (^) Zenith – the point straight overheadZenith – the point straight overhead (^) Meridian – line from North to southMeridian – line from North to south through zenith through zenith
CoordinatesCoordinates
(^) Just like the curved surface of the earthJust 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 Azimuth Altitude 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 Azimuth Altitude and Azimuth Celestial coordinatesCelestial coordinates
(^) Project Earth’s coordinates out into spaceProject Earth’s coordinates out into space (^) EquatorEquator (^) →→ Celestial equatorCelestial equator (^) PolesPoles →→ Celestial polesCelestial poles (^) LongitudeLongitude →→Right AscensionRight Ascension (^) LatitudeLatitude →→DeclinationDeclination
Celestial coordinates Celestial coordinates
Motion of the starsMotion of the stars
Motion of the StarsMotion of the Stars
(^) Depends on location, we will look at SouthDepends 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 atHave low altitude at the meridian the meridian (^) Set in SWSet in SW
SC, looking eastSC, looking east
(^) Stars rise alongStars rise along eastern horizoneastern horizon (^) Move up in at anMove up in at an angle towards theangle towards the southsouth
SC, looking westSC, looking west
(^) Move down towardsMove down towards the western horizon the western horizon an angle from the an angle from the south south
SC, looking north SC, looking north
(^) Some star rise is NESome star rise is NE and set in NWand set in NW (^) Others circle aroundOthers circle around the north celestialthe north celestial pole (circumpolar)pole (circumpolar)
Overview of SCOverview of SC^ Star pathsStar paths
(^) The path of stars are different in differentThe 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
Equator Equator
(^) Stars move from east to west moreStars 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
Equator Equator
North Pole North Pole
(^) North celestial pole at zenith (overhead)North celestial pole at zenith (overhead) (^) Stars are all circumpolar and move aroundStars are all circumpolar and move around at constant altitudes at constant altitudes
North Pole North Pole
SC, winterSC, winter
(^) Rises in SERises in SE (^) Reaches low altitude at noonReaches low altitude at noon (^) Sets in SWSets in SW (^) Night longer than dayNight longer than day
SC, spring SC, spring
(^) Rises in ERises in E (^) Reaches mid altitude at noonReaches mid altitude at noon (^) Sets in WSets in W (^) Day and night equalDay and night equal
SC, summer SC, summer
(^) Rises in NERises in NE (^) Reaches high altitude at noonReaches 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 noonReaches mid altitude at noon (^) Sets in WSets in W (^) Day and night equalDay and night equal
SC SC EquatorEquator
(^) Sun always moves more overheadSun always moves more overhead
EquatorEquator South CarolinaSouth Carolina
Alaska Alaska North PoleNorth Pole
South Africa South 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
