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Unformatted text preview: Astronomy 10, Fall 2008 Homework 3 - 40 points total Due in the boxes in the basement of Campbell Hall by 5pm Tuesday, September 23 . Be sure to include your name, SID, Section Number, and GSI name on your homework, and staple it together. 1. Extrasolar Planets (7 points) While scanning the sky with your trusty telescope and spectrometer, you find a bright star that is known to have a mass twice that of the Sun. You take a spectrum of the star and find that it shifts back and forth over the period of a week. In particular, you see an absorption line that normally has a wavelength of 588 . 995 nm move back and forth by 0 . 00137 nm Excited, you realize that the gravitational influence of a planet in orbit around the star is probably nudging it. (a) Assuming that the planets orbit is circular, what is the radius of its orbit? (Hint: Think about the general expression for Keplers Third Law.) (2 points) (b) Assuming that we are viewing the orbital plane of the planet edge on, what is the speed of the star as it wobbles around due to the planets gravity? (2 points) (c) Whenever two objects are orbiting each other, the product of the mass and speed of each object is the same: m 1 s 1 = m 2 s 2 . Using this fact and the information already found above, find the mass of the planet. (3 points) 2. Where is the Moon? (14 points) For each of parts (a) through (d) below, give your answers in compass directions (North, South, East, and West), and draw a diagram depicting the relative positions of the Earth, Moon, and Sun (as seen from above the north pole), and the location of the observer on the Earth for each case. In(as seen from above the north pole), and the location of the observer on the Earth for each case....
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