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

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!

Comments

third of three?

[Xtifr]

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.

Re:Problem with the definition of a planet

[meerling]

And don't forget that Pluto crosses Neptunes orbit as well.

Re:Astronomers don't want you to know this neat tr

[TapeCutter]

"Nobody ever asks about everyday phenomena" - Feynman complaining about people like you.