We discover vastly more exoplanets that are gas giants that orbit their parent star very closely, than small terrestrial planets that are more distant to their sun. Could this be due to the methods we use to find exoplanets?

Gas giants have stronger gravity which makes their star oscillate more. Moreover they are larger which eclipses more of the light of the star during transits? Are big hot Jupiters far easier to detect than small rocky worlds?

  • $\begingroup$ Yes, they are easier to detect. Can you clarify the main point of your question? $\endgroup$ Commented May 23, 2015 at 19:20
  • $\begingroup$ I want to know wether that is the reason why we detect more gasgiants than small rocky bodies. Or are there just more common? $\endgroup$
    – Astrony
    Commented May 23, 2015 at 20:49
  • $\begingroup$ See en.wikipedia.org/wiki/Methods_of_detecting_exoplanets. But you answer your own question: our observational methods detect the phenomena to which they are sensitive. $\endgroup$
    – andy256
    Commented May 24, 2015 at 6:07
  • $\begingroup$ @andy256 Of course, but my question is: Are we finding more gasgiants than terrestrial planets because they are more common, or because the methods we use tend to find gasgiants easier? $\endgroup$
    – Astrony
    Commented May 24, 2015 at 8:23
  • $\begingroup$ Because they are more common than what? Than in our system, or than other planets? Further, these factors are not necessarily mutually exclusive. As @andy256 pointed out, we're aware that our methods will more easily detect larger planets. It should follow naturally that the ratio is skewed by this. $\endgroup$ Commented May 24, 2015 at 10:18

1 Answer 1


Any statement about the relative frequencies of exoplanets of different size, is limited to the parameter space over which they can detected.

A recent analysis of the Kepler-discovered exoplanets, that takes account of observational selection biases, indicates that for planets orbiting with periods less than about 85 days, that "small Neptune"-sized objects (a few Earth-radii in size) are slightly more common (20%) than Earth-sized objects (17%), which are in turn much more common than Jupiter-sized objects (few %).

Extending this comparison outside this range of orbital periods is not possible with present data (though the paper was in 2013 and things may have now moved on a little).

I never did attach a reference: Here it is https://www.cfa.harvard.edu/news/2013-01


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