Polydeuces is an example of a so-called Trojan moon -- it is twinned with a larger moon in orbit around the planet (in the case of Polydeuces, the larger moon is Dione). Polydeuces is a trailing co-orbital of Dione, while the moon Helene is the leading co-orbital.
Trojan moons are found near stable "Lagrange points" -- places where the gravitational pull of the planet and the larger satellite become balanced. The Trojans are situated 60 degrees ahead or behind the larger moon in its orbit.
It is believed that Polydeuces can get as close as 39 degrees to Dione and then drift as far as 92 degrees from it, taking over two years to complete its journey around the Lagrange point. If verified, the extent of this wandering is the largest detected so far for any Trojan moon.
