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ET Lives in a Multi-Planet Solar System

  1. Feb 20, 2015 #1
    by Ken Croswell

    If ET exists, he probably lives in a solar system with many planets. That's the implication of a new study that finds that the more planets a solar system has, the more circular their orbits tend to be.

    Link (including a color chart showing the correlation of orbital eccentricity with number of planets in a solar system): Scientific American.
     
  2. jcsd
  3. Feb 20, 2015 #2

    mfb

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    Typical base rate fallacy in the article. A system with multiple planets might have a larger probability to have small eccentricities (which is not surprising), but without the fraction of systems with n planets this does not tell anything about the probability that life would be in multi-planet systems.
    Also, the diagram can be misleading: most planets are in the 1-planet category, so the dots would extend more towards larger eccentricities even without any correlation.

    Original paper (without that error)
    Figure 1 gives a better idea how large (or not large) the differences are.
     
  4. Feb 20, 2015 #3
    The authors recognize that most of the planets are in the 1-planet category but go through statistical tests to show that their result is statistically significant.

    The Scientific American diagram has exactly the same information as Figure 2 of the paper, except that it's presented in a more attractive manner.
     
  5. Feb 20, 2015 #4

    mfb

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    I didn't say anything against the publication, that looks good.
    The Scientific American article uses it to draw a conclusion that the data does not allow.

    Unfortunately that is the easiest one to misinterpret.
     
  6. Feb 20, 2015 #5
    The Scientific American story does not misrepresent the paper. The paper itself states, "If low eccentricities indeed favor high multiplicities, habitability may be more common in systems with a larger number of planets."
     
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