Planet Hunters Talk

Double planets

  • davidbundy77 by davidbundy77

    I couldn't help but wonder: do large double planets exist?

    Examples of stellar binaries are common and in our solar system there are examples of smaller planets with relatively large companions such as Earth-Moon, Pluto-Charon. As far as I know, no pairs of exoplanets have been discovered which orbit about each other. Large double planets ought to be detectable by now, if they are common. Indeed, the HEK project of Kipping et al. ( http://arxiv.org/pdf/1503.05555v1.pdf ) has made first attempts to quantify the limits of planet-moon combinations. Does anyone know if large double planets are ruled out by theoretical models of planet formation?

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  • ajamyajax by ajamyajax in response to davidbundy77's comment.

    Well, seems reasonable to assume they exist somewhere. But I don't remember seeing any news confirming large double planets just yet. We have guessed at such finds here, but it has been difficult to rule out other more plausible explanations so far anyway.

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  • BoulderAstroBadger by BoulderAstroBadger

    I was thinking that an Earth size moon around a Neptune sized planet close to a red dwarf star relatively close to the sun should be detectable by transit method. I don't have the expertise yet to analyze whether this is practical. Any thoughts?

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  • ajamyajax by ajamyajax in response to BoulderAstroBadger's comment.

    It would be best if you read what the experts are saying, but my guess is Earth-sized moons are rare. If ours was formed by collision with another rocky planet, maybe the chance of one orbiting a Neptune sized gas giant is that rare or even more so. Unless it was captured as the retrograde orbiting moon Titan is theorized to have been by Neptune. Anyway, something to think about.

    But most of us have looked at many planets here.. And in doing that my believe is the chance we have seen exomoons in those light curves is 100%. The difficulty is recognizing their very faint reoccurring signals and then proving that. So you could be the first if you think of something clever. 😃

    p.s. just looked it up and our Moon is the fifth largest moon in the Solar System. And there are some 166 satellites orbiting planets depending on how those are classified I believe.

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  • BoulderAstroBadger by BoulderAstroBadger

    Just what I was thinking of giving a try. A first step could be to work with a team to identify and confirm some nearby Neptune sized planet candidates from K2 data. The Planet Hunters VII paper on long period planets would seem to be a good template. If anyone is working on a project like this, I would love to help!

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