Astronomy 1021 Chapter Notes - Chapter 2: Circumpolar Star, Celestial Equator
28 May 2018
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Astronomy 1021
Chapter 2: Discovering the Universe for Yourself
Variation with latitude:
•Latitude- measures north-south position on Earth; it is measured north or south of the equator; latitude
is 0o at the equator, 90oN at North Pole, 90oS at the South Pole
•Longitude- 0o along the prime meridian- passes through Greenwich, England; it is measured east or
west of the prime meridian
•Latitude and longitude pinpoints a location on Earth
•Latitude affects constellations b/c it affects the locations of the horizon and zenith relative to the
celestial sphere
•Latitude= North pole star’s altitude
•Latitude affects what you can see, longitude affects when you can see it
•Pointer stars of the Big Dipper point to the North Star Polaris, 1o of north celestial pole, sky appears to
turn counter-clockwise around the north celestial pole
•Southern Cross points to the south celestial pole, not marked by any bright star, sky appears to turn
clockwise around the south celestial pole
•Sky does not vary with longitude, only latitude; ex. people in cities close to each other will see the same
constellations
•The sun remains above the horizon for 6 months at the North Pole- sun is north of the celestial equator
for half of each year, so in these 6 months it circles the sky at the north pole like a circumpolar star
•Latitude is declination (dec, ); equator is celestial equator; longitude is right ascension (RA, a);
Greenwich is vernal equinox
Variation with time of year:
•Sun’s apparent location along the ecliptic determines which constellations we see at night
•Sun appears to move eastward along the ecliptic as Earth orbits around the Su, so we see the Sun
against background of different zodiac constellations at diff. times of year
