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3 Questions - Why are some orbits

  1. Apr 8, 2005 #1
    More eccentric than others? is it because of the star they revolve around, the mass of the planet?

    And is there a limit to an eccentricity of a planet's orbit so it could support life, how much eccentricity is too much for the planet to be inhabitable?

    And is it true that it is easier to detect planet with high eccentric orbits?
  2. jcsd
  3. Apr 8, 2005 #2


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    Orbits generally begin eccentric, since the dust particles making up a star-forming nebula are not arranged in a spherically symmetric fashion; it actually takes some mechanism to circularize them.
    Human life wouldn't be able to withstand much eccentricity at all, but no one knows how many different kinds of life there might be. Your questions are good, but no one knows the answers.
    My first instinct is that it would be easier; after some careful thought, I think it might not make any difference, at least with the Doppler detection current being performed. The amplitude of the wobble is the most important criterion for detection, not the shape of the wobble's waveform. Perhaps someone with more first-hand knowledge than I can better answer.

    - Warren
  4. Apr 8, 2005 #3


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    Aside from what chroot mentioned, you can also make an eccentric orbit by a simple collision or a tidal perturbation from a nearby massive object. It's believed that comets are sent into eccentric orbits by one of these two mechanisms. There was even a theory that the periodicity of mass extinctions on earth was a result of a massive object in the Oort cloud that would periodically perturb large numbers of cometary orbits and send them plowing into the inner solar system.
  5. Apr 9, 2005 #4
    I can numerically illustrate Chroot and ST's comments - (What ST just said and Chroot's comments about the limited variation in orbit that permit life as we know it to thrive)

    A small change in Earth's orbit, even with little change in the annual solar heating, will kill most people - Choot is right about this and ST about how easy it is to change orbits with a mass passing by.
    Last edited by a moderator: Apr 9, 2005
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