Saturn's colossal ring

摘要

A hitherto undetected disk of debris around Saturn is the largest ever found to be orbiting a planet. This ring may hold the key to one of the most enigmatic landscapes in the Solar System. On page 1098 of this issue, Verbiscer and colleagues report the discovery of an enormous ring around Saturn. The authors found this most tenuous of Saturn's known rings, which covers some 10,000 times as much area as the planets photogenic main rings, by using the Spitzer Space Telescope to detect the ring's faint glow in the thermal infrared region of the electromagnetic spectrum. The ring is composed of dust, probably derived primarily from Saturn's distant moon Phoebe. Its discovery lends support to an earlier theory that dusty material from Phoebe is responsible for colouring the two-toned moon Iapetus.