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Unformatted text preview: Astronomy exam 1 chapter 2, lectures 2-9 Astronomical unit (Au): the average distance between the sun and earth. Light year (ly): the distance light travels in one year-----1trillion kilometer Distance = masses x speeds Galaxy: spirals and elipticals, our galaxy is MILKY WAY, g alaxies are large systems of stars and interstellar matter. Earth: r = 6400 km 1au from sun, orbital period:1 yrs Jupiter: 5AU from sun, orbital period:12yrs Neptune: 30AU from sun, orbital period: 165yrs Moon: of the earths diameter; next to earth;orbits the earth 27days; Keplers three laws : effects of the sun's gravity 1 An ellipse, the sun at one focus 2 specifies precisely how fast the planet moves at each point in the orbit (move fastest when closest to the sun) 3 P 2 = A 3 P = orbital period in years A = average distance from the sun in AU Newtons law of gravity and the meaning of all the terms in the law : F = G M 1 M 2/ D 2 g~m M1 and M2 are the masses of the two objects(g) D is the distance between the two masses (cm) F is the force between the two masses (dynes) G is a constant The minus sign means that gravity is an attractive force. Newtons modification of Keplers third law: ( M 1 + M 2 ) P 2 = a 3 , and how to find the masses of stars from Keplers third law. The Earth: 78% nitrogen, 21% oxygen, with trace amounts of everything else. It is currently 0.03% carbon dioxide. Interior of earth : Earthquakes set off waves in the Earth called seismic waves . There are two main types of waves Shear waves or S-waves: Molecules vibrate in a direction perpendicular to the direction the wave is traveling. (can travel through liq. & gas and materials that is strongly connected * rigidity * ) Pressure waves or P-waves: Molecules vibrate in the same direction as the wave is traveling. (particle is perpendicular to the wave; can travel through solids, liquids, and gases.) Interior of earth:...
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This note was uploaded on 03/02/2010 for the course AST 00000 taught by Professor Edwardl.robinson during the Fall '10 term at University of Texas at Austin.
- Fall '10