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Our Solar System: Rare Species In Cosmic Zoo 197

Posted by samzenpus
from the best-in-class dept.
astroengine writes "Pulling from 20 years of research since the first discoveries of planets beyond our solar system, scientists have concluded that Earth and its sibling worlds comprise what appears to be a relatively rare breed in a diverse cosmic zoo that includes a huge variety of planet sizes, orbits and parent stars. The most common systems contain one or more planets one to three times bigger than Earth, all orbiting much closer to their parent stars than Earth circles the sun, says astronomer Andrew Howard, with the University of Hawaii."
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Our Solar System: Rare Species In Cosmic Zoo

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  • Observation Bias (Score:5, Informative)

    by Anonymous Coward on Thursday May 02, 2013 @11:42PM (#43617465)

    I was under the impression that this was agreed to be due to observation bias. That is, it's a hell of a lot easier to find planets bigger than Earth orbiting at frequent, highly periodic intervals than to find anything else.

  • Re:God made it. (Score:5, Informative)

    by Cinder6 (894572) on Friday May 03, 2013 @12:59AM (#43617687)

    To be fair, TNG did explain why (most) aliens were humanoid in the episode The Chase.

  • Re:Observation Bias (Score:4, Informative)

    by TuringCheck (1989202) on Friday May 03, 2013 @01:06AM (#43617709)
    3 is a very conservative minimum - usually more orbits are needed to improve the signal / noise ratio by averaging.

    For K averaged orbits the S/N ratio improves by sqrt(K) so detecting planets that cause just small variations drowned in a lot of noise becomes quickly impractical...

  • by bruce_the_loon (856617) on Friday May 03, 2013 @02:46AM (#43617991) Homepage

    Precisely. Kepler's been up and observing for 4 years now. Since it hunts for occultations, the scientists can only be certain that observed planets are alone out to a 4 year orbit, which excludes anything outside of Mars in our system. And that is if the system is aligned so that the orbital plane is correctly positioned for Sol-visible occultations.

    For a star where Kepler has observed something, they can only say there's no planets inside 4 year orbits, everything else is speculation. For a star where nothing has been observed yet, they can't say anything with certainty.

  • Re:God made it. (Score:4, Informative)

    by Intrepid imaginaut (1970940) on Friday May 03, 2013 @04:30AM (#43618283)

    The Universe is so large that it cannot possibly be that we are the only life thriving on a planet orbiting a star.

    Unfortunately it quite possibly can. Since we have only one instance of life on record, in the absence of further evidence all we have is conjecture. We might very well be alone in here.

  • by dimeglio (456244) on Friday May 03, 2013 @05:31AM (#43618449)

    The book Rare Earth dwells into the possibility we're in fact quite exceptional. I've seen plenty of debate regarding some of the statements and conclusions drawn by the authors but nonetheless, "intelligent" life seems a lot less common than expected. That being said, we're improving our "life detection" skills and it might be possible, in a few years, to actually "scan" a planet from earth and detect elements, through spectrum analysis [labspaces.net], which point to evidence of life.

  • Free ArXiv version (Score:3, Informative)

    by amaurea (2900163) on Friday May 03, 2013 @07:54AM (#43619087) Homepage

    The actual article is much better than the one linked in the story. A version very close to the one published in Science can be found here [arxiv.org], at the public preprint archive (arXiv). The article should be relatively easy to read even for non-scientists. Note that our knowledge of the distribution of planets is marred by the biased sample we have access to: It is much easier to observe planets if they are close to their parent star, and heavy. Most of the statistics provided in the article attempts to correct for this bias, so we can say pretty confidently that small planets are much more common than large ones*. But the other claim in the summary, that most planetary systems are much more compact than the solar system, doesn't seem to be supported in the article itself. But perhaps I missed something.

    Anyway, the Science article is readable, and if nothing else the figures are quite interesting.

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