HW#1Astronomy

# HW#1Astronomy - For the orbital periods use the absolute...

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Planets and Planetary Systems Astronomy 138 - Fall 2010 Homework #1 Due Tues. Aug. 31st, 1:25 pm 1. What are circumpolar stars? Are more stars circumpolar at the North Pole or in the United States? Explain. Circumpolar stars are stars that never actually set from a given latitude on earth because of their proximity from either celestial pole. Since the United States is lower on the latitude lines than the North Pole, some stars would become invisible along the horizon. Therefore, more circumpolar stars are visible from the North Pole, not the United States. The closer the person is to the north celestial pole, the more circumpolar stars they will be able to see orbiting that particular celestial pole. 2. Plot the orbital period vs. orbital distance (semi-ma jor axis) for Saturn's 61 natu- ral satellites (moons). A table of their periods and distances from Saturn can be found at http://en.wikipedia.org/wiki/Saturn%27s_natural_satellites#Table_of_moons.
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Unformatted text preview: For the orbital periods use the absolute value in days and for the semi-ma jor axes leave the distances in kilometers. (Negative periods imply retrograde motion.) The graph can be computer generated or hand-written on graph paper. Compare with the graph in the Lecture Tutorials, p. 26. Do the natural satellites of Saturn obey Kepler's third law? Explain. Kepler’s 3 rd law states that, the square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit. As you can see from the following graph, the moons of Saturn do indeed follow Kepler’s 3 rd Law. In the graph, the x-axis represents the semi-major axis in km and the y axis represents the orbital period in days. The graph is a scatter plot connected by a line that appears to gradually increase at a steady rate....
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