Telesto

Telesto circles Saturn in step with the much larger Tethys. Rather than wandering freely along their shared orbit, it stays near the leading Lagrange point, about 60 degrees ahead of Tethys. The geometry lets this tiny moon keep roughly the same position relative to Tethys while both bodies travel around Saturn.

That makes Telesto one of Saturn's Trojan moons. Calypso occupies the corresponding trailing point behind Tethys, so the orbit contains a three-body arrangement: a major moon with one small companion leading and another following. Telesto turns the abstract stability of a Lagrange point into a visible natural system.

Cassini gave Telesto its clearest close view during a distant flyby in October 2005. The images showed an irregular body with a surprisingly smooth surface and few small impact craters. Telesto is therefore notable not only for where it travels, but also for a surface that looks unexpectedly subdued for such a small exposed moon.