The Planets: Saturn
Saturn is the farthest planet from Earth that can still be seen with the naked eye.
Saturn’s spectacular rings give the planet a distinctive appearance that captures the imagination in a way that few other celestial objects can. Named for the Roman god of agriculture, this sixth planet from the sun consists of swirling clouds of hydrogen and helium, giving Saturn a striped or banded appearance. More than four centuries of research have revealed many of Saturn’s secrets, though the Cassini spacecraft continues to provide even greater access to this faraway planet.
History and Exploration
Italian astronomer Galileo Galilei was the first person to make observations of Saturn through a telescope in 1610. At first, he thought the planet was surrounded on both sides by two sphere-shaped objects. Later he identified these objects as handles attached to the planet. By 1659, astronomers realized that Galilei’s handles were actually rings surrounding Saturn. Telescopes and other tools provided small glimpses into Saturn until 1979, when Pioneer 11 became the first spacecraft to reach the planet. In 1997, NASA launched Cassini, a craft that reached Saturn in 2004 and sent a probe to land on Saturn’s moon Titan in 2005. The Cassini mission was extended several times and should continue to provide new information through at least 2017.
Unlike the four planets closest to the sun, which are known as terrestrial planets due to their rocky surfaces, Saturn, Jupiter, Uranus and Neptune feature a gaseous structure. Saturn consists of hydrogen and helium mixed with small amounts of ammonia and methane gas, with a surface temperature of negative 176 degrees Celsius (negative 285 degrees Fahrenheit). High winds in excess of 447 meters per second (1,000 mph) blow across the surface of the planet. Saturn is so large that 700 Earths could fit within its boundaries.
Saturn’s multicolored rings span more than 282,000 kilometers (175,000 miles). They rotate around the planet at a variety of speeds, and the thickness and composition of each ring varies significantly. In general, Saturn’s rings consist of water, ice and rock, with particles ranging from as small as a speck of dust to as large as a house. While no one knows exactly why Saturn has rings, one theory suggests that the planet’s tremendous size gives it such a strong gravitational pull that it’s able to attract stray pieces of broken comets, asteroids and other debris to form its classic rings.
As of publication time, more than 60 known moons orbit Saturn. The best-known of these moons is Titan, which is not only the largest of Saturn’s moons but also the second largest moon in the solar system. Titan is about the same size as the planet Mercury and features an atmosphere of nitrogen and methane. Two other moons, Encke and Keeler, actually orbit Saturn in gaps between the planet’s rings.