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Kepler Orbit

  1. Mar 21, 2010 #1
    Sorry if this is in the wrong forum.

    I have the equation [tex]r = \frac{a(1-e^2)}{1+e \cos \theta} [/tex],
    and I'm wondering what the physical significance of the numerator is.
    More specifically, what is 'a' (since e is what it usually is)?

    I've seen various other representations with terms like angular momentum on the top (or rather h^2/GM).

    In the context of what I'm doing, it's written this way to (presumably) uncover any implicity 'e'-dependence in the orbit.
  2. jcsd
  3. Mar 21, 2010 #2


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    'a' is the semi-major axis of the orbit, or the average value of 'r' for the orbit.
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