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Homework Help: Mass of a star

  1. Oct 16, 2005 #1
    Suppose there is a planetary system in which a planet with an average distance of 6 AU from the star has an orbital period of 3 years. What is the mass of the star?

    The answer should be in SOLAR MASSES.

    I tried to use the formula: P^2 = (4pi^2*a^3)/G(m+M)
    but it didnt work:(

    any hint?
  2. jcsd
  3. Oct 16, 2005 #2


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    Science Advisor
    Homework Helper

    This is a simple variation problem and you should recognize that

    [tex]\frac {M P^2}{R^3}[/tex]

    is a constant so you can easily setup the appropriate proportion.
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