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What are causing the Eccentricity of the planets?

  1. Nov 7, 2008 #1
    What are causing the Eccentricity of the planets?
    When reaching Neptune we have nearly a completely circular orbit.
    Why ?
    It seems not to be any logic in this !

    Mercury 0,20563069
    Venus 0,00677323
    Earth 0,01670900
    Mars 0,09340100
    Jupiter 0,04849500
    Saturn 0,05550900
    Uranus 0,04629600
    Neptun 0,00898800
    Last edited: Nov 7, 2008
  2. jcsd
  3. Nov 7, 2008 #2
    Since the time the solar system was created, there have been lots of impacts onto planets caused by others objects either from outside of inside the system. The impacts are possible cause of the eccentricity.

    There's hardly any rule about the list. Just may be it seems to me: the smaller the planet, the easier it can be hit out of its original (nearly) circular orbit (and the tilt as well).
    Mercury, Pluto and Mars ...
  4. Nov 7, 2008 #3


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    Why should they be perfectly circular? Each planet in the solar system is also experiencing small tugs from all the other planets so a perfectly circular orbit would not last long.
  5. Nov 7, 2008 #4

    D H

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    Except for Mercury and Pluto, the planets in our solar system have very small eccentricities. Most exoplanets discovered to date have much highly eccentric orbits: circular (or nearly circular) orbits are not the norm. The standard models of planetary formation, which suggests nearly circular orbits will arise, need some tweaking.

    Collisions are not needed to explain the eccentricities in our solar system. All that is needed is gravity. Suppose the planets all had perfectly circular orbits. Gravitational interactions among the planets would quickly result in non-circular orbits. Our solar system is not stable. It is chaotic. Jupiter, being by far the most massive, is the largest contributor to this chaotic behavior. Mercury's orbit, for example, has a strong secular resonance with Jupiter's orbit.
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