That is the faint possibility raised by some simulations run by an astronomer Sean Raymond at the Laboratoire d’Astrophysique de Bordeaux in France. He and his colleagues have been running simulations looking at the formation and orbital evolution of planets, both in our own Solar System and further afield.
New Scientist magazine reports that Raymond’s latest research raises some interesting ideas. He explains that they had thought that if two planets happened to share the same orbit around their star that they would keep the same distance apart, sort of companion planets. However, the simulations showed that when this does occur, this is not always how they behave. Instead, some compete for position, their gravity sometimes slowing or speeding up the other and so causing it to fall closer or move further from the star in its orbit. Essentially swapping orbital distances.
This orbit traces the shape of a horseshoe and thus the name horseshoe orbit. The orbit is stable, despite their changing position. In our own Solar System, the only example is that of Saturn’s moons, Janus and Epimetheus, who impact each other in the same way.
The interesting bit is what could cause these orbits to form.
He says on his blog that “Maybe it’s possible, but I am guessing that it’s ridonkulously rare for horseshoe constellations to form naturally..”
Raymond goes on to say, “the alternative is that horseshoe constellations might be produced by orbital engineering done by highly advanced civilizations. If such a civilization wanted to leave a mark of its existence that would be both long-lived and detectable from astronomical distances, a horseshoe constellation would be a good candidate.”
However, it is worth pointing out that although these systems occurring in simulations means the likelihood of them existing is higher, it does not mean they do. Other researchers have said that it would be very difficult to detect such a setup, but Raymond believes it would be possible, perhaps when the planets were in transit across their star.
You can read more about Raymond’s work on his blog.