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2 Planets Can Share the Same Orbit, In 3 Different Ways 73

StartsWithABang writes: One of the most important characteristics of a planet, at least according to the IAU definition, is that it clear its orbit of all other bodies. But if we allowed for a special caveat — the possibility of two similarly-sized objects sharing the same orbit — could we have a stable configuration where that occurred? Surprisingly, not only is the answer yes, but there are three ways to do it: to have one at the L4/L5 Lagrange point of the other, to have a close-orbiting binary planet, or to have orbit-swapping worlds, where they periodically change spots with one another. Unbelievably, our Solar System has a history of all three!
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2 Planets Can Share the Same Orbit, In 3 Different Ways

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  • 2 planets (Score:2, Funny)

    by Anonymous Coward

    One Orbit

  • by balsy2001 ( 941953 ) on Sunday November 29, 2015 @03:19AM (#51020761)
    Given that the third mass needs to be negligible for the Lagrange points to work (at least according to Wikipedia), to me it seems like this situation might be more like a strange type moon rather than a planet. What is or isn't a "planet" is just a random definition so there isn't really a right answer.
    • by Ormy ( 1430821 )
      The 'negligable mass of the third body' applies in almost all situations. An exception (as I recall from astrophysics&cosmology) is when two objects share L4/L5 points of each other while both orbiting a much larger mass (as in two small planets orbiting a star, the first is in the second's L4 and the second is in the first's L5).
  • How many different ways are there to rehash shit that everybody knew since forever into crappy clickbait articles?

    • This is an article for "Memento" like people.
    • Re: (Score:2, Informative)

      by Anonymous Coward

      How many different ways are there to rehash shit that everybody knew since forever into crappy clickbait articles?

      This. Seriously, I'm getting sick of having Ethan's blog everywhere I go. Guy's good at manipulating social media, but there's nothing on any of his post that isn't just a rehash of things that Slashdot and other tech/science blogs have already linked to years ago.

    • by Anonymous Coward

      Speak for yourself. I read the whole article, and enjoyed it. Not everyone knows all the intricate details of planetary orbits.

  • third of three? (Score:5, Insightful)

    by Xtifr ( 1323 ) on Sunday November 29, 2015 @04:32AM (#51020857) Homepage

    One of the most important characteristics of a planet...

    There's three characteristics, and this is probably the least important. But if you consider all three to be "the most" important, then I suppose it's one of them. That seems like a pretty silly way to express yourself, though. Personally, I'd probably just say "one characteristic".

    Also note that we're talking about the IAU definition, which is not necessarily the only definition. Dictionaries still haven't accepted the IAU definition, and may never do so, because the IAU defines a planet as orbiting the sun, while science fiction writers continue merrily talking about planets around other stars, and show no signs of changing.

  • by ArsenneLupin ( 766289 ) on Sunday November 29, 2015 @04:55AM (#51020873)
    ... please at least check whether the links in the submission are going anywhere...
  • by AmiMoJo ( 196126 ) <mojo@@@world3...net> on Sunday November 29, 2015 @05:33AM (#51020925) Homepage Journal

    Can we please have warnings on links to Forbes? Those interruptions for their (usually stupid) "thought of the day" are really annoying. Perhaps editors should look for alternative sources where possible.

  • And ends with me leaving Slashdot for a few months.
    Enough of this SWAB crap!

  • Exactly on other side of Sun so you would never see it. But I dont think this is stable. Also since Earths orbit is ellipitical, the speed is not uniform through ot the year. So part of the years wouldnt be halfway apart and possibly visible.
    • Correct on both objections.

      Yes, it is unstable. Any discrepancy from precise balance will be exacerbated, and the presence of the Moon alone (ignoring effects, such as that due to Jupiter) is sufficient to perturb this system, leading to either a close encounter, or a Trojan- Greek relationship.

      Your second consequence follows from the first.

  • The Ringworld is unstable!!!

"I have not the slightest confidence in 'spiritual manifestations.'" -- Robert G. Ingersoll