| Astrophysics (Index) | About |
A shepherd moon is a small moon at the outer edge of a planet's ring or in a gap between rings, whose presence helps shape the ring, in particular to make the edge "sharp". Examples:
| planet | shepherd moons |
| Jupiter | Metis, Adrastea |
| Saturn | Pan, Daphnis, Prometheus, Janus, Epimetheus |
| Uranus | Cordelia, Ophelia |
| Neptune | Galatea |
Saturn moons Atlas and Pandora have been considered shepherd moons: they are similarly positioned, but a determination has found that their presence does not significantly affect the rings that they border.