At least 18 moons orbit Saturn. Until recently, Saturn was the moon champion, recognized as having more than any other planet in the Solar System. However, astronomers have announced discoveries of additional moons around Uranus, bringing that planet’s total to 20 if the observations are confirmed. There are probably many additional small moons amidst Saturn’s rings, and the Cassini mission may find some of them. Saturn’s 18 moons are listed in the table on page 240, along with their distances from the center of Saturn, orbital periods (time to go once around Saturn), sizes, and notable features. The smallest moons (Pan, Atlas, Prometheus, Pandora, Epimetheus, Janus, Telesto, Calypso, Helene, Hyperion, Phoebe) have irregular shapes. For these moons, an average “radius” has been calculated by averaging measurements of their sizes in three dimensions. The larger moons (Titan, Rhea, Iapetus, Dione, Tethys, Enceladus, Mimas) are very close to being spheres. Just like Earth’s Moon, most of Saturn’s moons rotate at the same rate as they revolve around Saturn, and thus keep the same face toward Saturn. This also means the moons always have one side that faces toward the direction of their motion around Saturn, and one side that faces away from their direction of motion. These are called the leading and trailing hemispheres.