Trojan moon

A Trojan moon is a natural satellite of a planet occupying the L₄ or L₅ equilateral Lagrangian points of a primary-moon system. They are named by analogy with the Trojan asteroids, which occupy the L₄ and L₅ points of the Sun-Jupiter system.

Four examples are known, all in Saturn's system: Telesto and Calypso bracket Tethys, whilst Helene and the newly discovered Polydeuces bracket Dione. The Earth-Moon points have been repeatedly searched for Trojans, but nothing else than a slight overabundance of dust has ever been found.