Astr. 101 Notes

Astr. 101 Notes - -diurnal movement-day and night on...

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-diurnal movement-day and night on Earth, the Earth rotates once per day around its north/ south axis (how do we know this? Sun, stars moving east to west; Sun and stars rise and set though out diurnal cycle) -but Sun and stars are not actually moving like this, the Earth is rotating in the opposite direction, west to east (from the north, Earth’s rotation is counterclockwise; from the south, Earth’s rotation is clockwise) -imaginary celestial sphere-there is an imaginary sphere encircling universe, all stars are “painted” on walls of this sphere; stars at different distances all appear to lie on sphere, but their relative positions remain fixed over our lifetimes; the ecliptic is the sun’s apparent annual path through the celestial sphere -88 official constellations cover the celestial sphere -circumpolar stars-never set, above either north or south poles (stars on opposite pole from your hemisphere never rise) -local sky-an object’s altitude (above horizon) and direction (along horizon) specifies its location in your local sky -zenith-point directly overhead -horizon-all points 90 degrees away from zenith -meridian-line passing though zenith and connecting N and S points on horizon -specify position on Earth using longitude, latitude -angle of right ascension-circumference of celestial sphere parallel to equator of Earth (measured in time) -angle of declination-analogous to latitude in the celestial sphere -angles and angular measure-angular diameter of full moon is about ½ degree, Big Dipper is about 5 degrees (northern hemisphere), Southern Cross is about 6 degrees (southern hemisphere) -full circle=360 degrees, 1 degree=60’ (arcminutes), 1 arcminute=60’’ (arcsecond) -Earth orbits sun in ecliptic plane at 23.5 degree tilt (same direction/ tilt no matter where
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This note was uploaded on 05/13/2011 for the course ASTR 101 taught by Professor Christiansen during the Spring '08 term at UNC.

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Astr. 101 Notes - -diurnal movement-day and night on...

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