National Geographic : 1953 Jan
128 Mount Wilson and Palomar observatories Saturn's Gigantic Halo: Tiny Particles, Each Moving in Its Own Particular Orbit, Form the Ring System Twice during Saturn's 30-year revolution around the sun, the three main concentric rings present a knife-blade edge tothe earth. Here they tiltjust enough to reveal their circular shape but not their triple nature. Two black blobs at either end represent all that may be seen of one circular separation band. Composed possibly of material which never formed a satellite, the rings are 171,000 miles in diameter but only 10 miles thick. Though semitransparent, they are solid enough to cast a shadow on Saturn. The shadow of Saturn's globe here blots the rings at the left.