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Homework Help: Finding Period with Double Stars

  1. Apr 26, 2009 #1
    1. The problem statement, all variables and given/known data

    A certain double star consists of two identical stars, each of mass 3.0E30 kg, separated by a distance of 2.0E11 m between their centres. How long does it take to complete one cycle? Give your answer in seconds.

    2. Relevant equations

    Gm / 4π^2 = r^3/ T^2 (I'm pretty sure the motion will be elliptical)

    3. The attempt at a solution

    I tried the above equation, and isolated for T, but I got the wrong answer. The answer is 7.9E7 seconds.
  2. jcsd
  3. Apr 26, 2009 #2
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