cheat sheet 1

cheat sheet 1 - Summer solstice sun at northernmost pt...

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Summer solstice: sun at northernmost pt above celestial equator, June 21, longest day in N; Winter Solstice: sun at southernmost pt below celestial eq., Dec 21, shortest day in N; Autumnal Equinox: Sept 21, 12 hr day, axis not towards or away from sun; Vernal Equinox: Mar 21; Earth rotates 360° every sidereal day which equals 24 sidereal hours which equals 23:56 solar hours; Sidereal Yr: 20 min longer than tropical yr bc Precession: change in rotation axis of spinning obj. 26,000 yrs, gravity of sun and moon cause; Sidereal Month: moon takes 27.3 days to complete one revolution and returns to same spot on celestial sphere; Solar Day= 24 solar hrs. Tropical Year: Earth revolves 360° every 365.24days. Synodic Month: time takes moon to go through phases 29.5 days; Wax: growing; Wane: shrinks; Lunar Eclipse: sun earth moon; Solar Eclipse: sun moon earth; Annular Eclipse: when the moon is far enough from earth so when it passes in front of the sun but fails to cover the sun completely, the umbra never reaches earth, thin ring of sunlight visible around the moon, roughly half of all solar eclipses are annular; Saros Cycle: time between recurring eclipses (223 lunar months OR 6,585 1/3 solar day), eclipses occur 19 days earlier each year ( Eclipse Year: 346 days) because Line of Notes regresses. Because of the extra 1/3 day, Earth rotates an additional 120° and consequently the eclipses do not reoccur at the same longitudes compared to the last cycle. Geocentric: Earth is center of universe, Fixed stars, Everything rises in East and sets in West, Sun and Moon have a uniform W E motion wrt fixed stars, Planets go through a retrograde cycle : non-uniform motion, Brightness variation: planets brightest in retrograde, Mercury and Venus always closest to the sun
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This note was uploaded on 01/22/2012 for the course ASTR 101 taught by Professor Christiansen during the Fall '08 term at UNC.

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cheat sheet 1 - Summer solstice sun at northernmost pt...

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