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### 20 Cards in this Set

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 How old is the sun? 4.55 billion years old How far apart are the moon and the earth? about 1/4 of a million miles apart How hot is the corona of the Sun? The corona, or outer atmosphere of the Sun, is 2 million degrees Kelvin or 4 million degrees Farenheit. How many stars are in the Milky Way? Write answer in scientific notation as well. 400 billion stars, or 4 X 10^11 Approximate the number of stars in the universe. 4 X 10^11 X 10^9 = 4 X 10^20 10^-6 m = 10^-9 m = 10^-10 m = 1 micron 1 nano-meter 1 Angstrom What is the distance between the Sun and the Earth? 1 AU = 1.5 X 10^8 km = about 93 million miles 1 lightyear = 1 parsec (pc) = speed of light = 9.46 X 10^12 km 3.26 ly = 3.09 X 10^13 km 300,000 km/s What are the apparent naked-eye movements of the heavens? The stars remain fixed. Objects in the sky move from E to W in a day. The moon moves W to E in a month. The sun has a N and S altitude change in a year that determines the seasons. One rotation = One revolution = tilt = 23 hours, 56 minutes 365.24 days 23.5 degrees What are the seasons caused by? The directness of the sun's rays. In the Northern hemisphere summer, there are more vertical rays. What is the current north star called? Polaris Explain what causes retrograde motion. The earth has a smaller orbit and moves faster than planets and objects that are further away from the Sun than the Earth. 1 degree = 1 arcminute = 1 finger width = one hand width = Moon's angular size = 60 arcminutes, 60' 60 arcseconds, 60" 2 degrees 10 degrees 1/2 degree small-angle formula D = (a x d)/206,265 D = linear size of object a = angular size (in arcsecs) d = distance to the object How long is the Moon's orbital period? sidereal or real is 27.321 days, time to go around the celestial sphere synodic or apparent is 29.531 days, from New moon to New moon, because Earth orbits the Sun When do the full moon, new moon, and 1st quarter moon rise and set? full moon rises at sunset and sets at sunrise new moon rises at sunrise and sets at sunset 1st quarter moon rises at noon and sets at midnight What is synchronous rotation? Also called spin orbit coupling, the moon orbits the earth and rotates around its axis in the same amount of time solar eclipse rare, new moon, near a node or where orbit crosses the ecliptic plane, darkest or total part is the umbra, partial eclipse area is the penumbra, moon is in between the sun and the earth, if angular size of the moon is less than the sun you have an annular eclipse which occurs when the moon is far from the earth lunar eclipse common, earth in between sun and moon, full moon and near a node