Inner shepherd of Saturn’s ropy F-ring, Prometheus casts a long shadow through the ring’s icy haze in this beautifully reworked Cassini image by Gordan Ugarkovic. Discovered by Voyager in 1980 Prometheus completes a tumbling orbit around Saturn every 14.7 hours, regularly dipping into the F-ring in a scalloped path and pulling out streamers of icy…