Bruce Murray Space Image Library

Prometheus' interaction with the F ring

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This movie sequence represents almost one complete orbit of Saturn by Prometheus, the inner shepherd of the F ring. Both the F ring and Prometheus have slightly elliptical orbits, so, once each orbit, Prometheus wanders in to the dusty lanes of the F ring. As it moves back toward Saturn, Prometheus drags a streamer of dusty material behind it. Because Prometheus is closer to Saturn than the F ring, it orbits slightly faster, so the streamer lags behind Prometheus in its orbit. On the next pass around Saturn, Prometheus will intersect the F ring at a position 3.2 degrees of longitude ahead of this streamer, creating a new streamer. Over time, the streamers disappear. Cassini has seen as many as 15 streamers behind Prometheus in its orbit. The 72 images for this animation were taken 10.5 minutes apart over 23 and 24 November 2006. They have been reprojected to straighten out the F ring, showing the actual radial distance between Prometheus and the ring. The dark frames represent the period during which Prometheus and the F ring are eclipsed by Saturn's shadow.