shepherd satellite

…moon, Prometheus, have been dubbed shepherd moons because of their influence on ring particles. During Voyager 1’s flyby, the two bodies were discovered orbiting on either side of the narrow F ring, which itself had been found only a year earlier by Pioneer 11. The moons’ gravitational interactions with the…

…spreading in a process called shepherding. Certain orbits that lie inside or outside the orbit of a given ring are at the proper radius for a moon in such an orbit to establish a stable dynamic resonance with the ring particles. The condition for the resonance is that the orbital…