SATURN - THREE RINGS

Saturn, the sixth closest planet to our Sun, was the most remote planet known to ancient man. Saturn must have been known even in early times because, at its brightest, it outshines all stars except Sirius and Canopus. Saturn is named for Jupiter's father, the first ruler of Olympus. The planet was formed about 4.6 billion years ago from gas clouds.

CHARACTERISTICS

Saturn's mass is about 95 times greater than Earth's, making it the second most massive planet behind Jupiter. However, Saturn is the least dense planet of our solar system. Its large outer layers of gases like hydrogen and helium surround a liquid hydrogen interior. The gaseous nature of Saturn causes its period of axial rotation (the length of a day on Saturn) to be differential.

RINGS

Saturn is, of course, best known for its rings, which make it arguably the most beautiful object in the night sky. These rings puzzled early astronomers like Galileo, who decided in 1610 that "the planet Saturn is not one alone, but is composed of three, which almost touch one another and never move nor change with respect to one another." The truth about Saturn's rings was given in 1659, in Christiaan Huygens' Systema Saturnium. There are three main rings, named A, B, and C. Rings A and B are brightest, while ring C is semitransparent and less evident. Smaller rings D through G have been observed in recent years, but they are largely insignificant. In fact, there are literally thousands of rings with tiny gaps between them. The rings are made of particles of debris, which range from the size of a grain of sand to tens of meters in diameter.

MOONS

Saturn has 23 satellites (moons), by far the most of any planet in the solar system. The largest is Titan, which is 5,150 km in diameter. Other satellites of significance include Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus, and Phoebe. Phoebe, the farthest moon from Saturn, has an oddly angled orbit much wider than the other moons, suggesting it was perhaps once an asteroid that became entrapped by Saturn's gravitational pull.