ASTR lecture notes - Reference Systems Sky Celestial sphere,equatorNorth\/south celestial ascension(imaginary concepts NCP is Polaris the north starSCP

ASTR lecture notes - Reference Systems Sky Celestial...

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Reference Systems: Sky- Celestial sphere,equator…North/south celestial Pole…Declination…Right ascension (imaginary concepts) NCP is Polaris, the north star…SCP is never visible from this far north Declination=latitude but in the sky Earth- Surface, equator, North/South Pole, Latitude, Longitude o Why earth isn’t flat: Lunar Eclipse: Earth’s shadow is cast upon the moon…the shadow was an arc; therefore, the object is circular Oceans: the oceans bulge so two ships cant see eachother decks since the other boat is below the curve. Magalenic Clouds: Magellen went far enough south to see stars/galaxies that no one in Europe had seen before. Divernal Motion The earth (from looking down at the north pole) is rotating counter-clockwise At north pole: the NCP is directly overhead…the stars are always level At equator: All stars rise and set (you can see all the stars)…NCP and SCP are on horizon..stars go up and down Latitude: The angle to the horizon..some stars are circumpolar,rise and set, and some are never visible Celestial Equator: where the sun path is on Mar21, sept22 (autumnal and vernal equinox)… Autumnal= sun is moving southward…Vernal= northward Winter soltice= Dec.21…Summer soltice= June 21 Precession=(think of spinning top) circular motion but takes a long time (25,800 years) it’ll rotate 47 degress away Earth goes around the sun in a counter-clockwise motion 8/31/11 Earth’s tilt= 23.5 degrees Ecliptic= apparent path of the sun around the celestial sphere Elicptic and celestial equator are separated by 23.5 degrees Equinox=ecliptic and the equator cross Winter solstice= sun is farthest south from the celestial equator…summer solstice is north The changes in season DON’T mean we are closer to the sun in summer than winter..its the tilt of the earth. Solar constant=1370 Watts/meters^2…AT BEST the sun delivers this much energy (its is actually less due to the ozone and radiation) Sun is high in the sky…more energy…hotter and vise versa The sunlight is closer to perpendicular in summer EARTH= Ellipse, Sun at Focus, Counterclockwise, Ecliptic, 365.26 MOON= Ellipse orbit, Earth at focus, Counterclockwise, tipped 5degrees from ecliptic, 1 month 9/7 The Moon New moon= when moon is between earth and the Sun
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Sidereal Month= time it takes the moon to do an orbit…27.3days…This is the new moon so the new moon isn’t always between the Earth and the Sun therefore lunar eclipses don’t always happen. Synodic Month= the moon actually has to go a little bit farther since the Earth is moving as well…29.5days The moon is always half lit Synchronous rotation: The moon spins counterclockwise…it takes the same amount of time for the moon to spin as it does to orbit the Earth…Therefore; we always see the same side of the moon Phases: determined by how much of the bright side we see…light goes from RIGHT to LEFT till full…then darkness goes RIGHT to LEFT till New Moon Right side is bright…Waxing (means getting bigger)
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