This week, Jonathan asked us if it's possible for two planets to share the same orbit. Naked Scientist Graihagh Jackson put this to Dr Stuart Higgins from Cambridge University...
Yes alancalverd, Mon, 7th Mar 2016
But not if there are other large bodies in the same system. Then the disturbance from gravity from them will destabilise the orbits in a few million years quite a lot. This, like a Lagrange point, is only true in a system with 3 masses and is stable. Add more and the stability is not true over long periods. SeanB, Mon, 7th Mar 2016
Haha, funny, is this a trick question?
Would it matter how big two planets were in the same orbit?
how did this thread get under pheromones? cheryl j, Sun, 13th Mar 2016
The scientists seem to have answered a different question to the one asked. The questioner asked if two planets could share the same orbit, not if they could orbit around each other. I think the questioner may have been wondering if a second planet could share the same orbit as Earth but be on the other side of the Sun for example Russell, Sat, 9th Apr 2016
There are a couple of naming errors to point out here: Pluto's moon is Charon, not Sharon. And most importantly, the twin-sunned word in Star Wars was called Tatooine, not Dantooine :) PhilJ, Thu, 14th Apr 2016
One way to answer the question of whether two planets can use the same orbit, is to first look at the planet Saturn and its moons. The moons of Saturn do not use the same orbit, but the rings of Saturn do use the same orbit. The difference, I see, has to do with the amount of gravity in the sub-units of the entries in the same orbit. The ring is composed of small units, each of which have limited gravitational impact on each other. We have tons of space debris orbiting the earth some of which uses the same orbit. The moons of Saturn have more gravitational influence on each other.