Saturn is the sixth closest planet to the Sun and the second largest planet in the solar system. Saturn’s rings are extraordinarily thin. Though they’re 250,000 km or more in diameter, they’re less than one kilometer thick. The ring particles seem to be composed primarily of water ice, but they may also include rocky particles with ice coatings. Saturn is visible with the unaided eye. The rings and larger moons are visible with telescopes. Saturn has 18 named moons plus 12 recently discovered unamed ones.