Saturn

Saturn was the most distant of the five planets known to the ancients. In 1610, Italian astronomer Galileo Galilei was the first to gaze at Saturn through a telescope. To his surprise, he saw a pair of objects on either side of the planet. He sketched them as separate spheres, thinking that Saturn was triple-bodied. Continuing his observations over the next few years, Galileo drew the lateral bodies as arms or handles attached to Saturn. In 1659, Dutch astronomer Christiaan Huygens, using a more powerful telescope than Galileo's, proposed that Saturn was surrounded by a thin, flat ring. In 1675, Italian-born astronomer Jean-Dominique Cassini discovered a division between what are now called the A and B rings. It is now known that the gravitational influence of Saturn's moon Mimas is responsible for the Cassini Division, which is 4,800 kilometers (3,000 miles) wide.

Like Jupiter, Saturn is made mostly of hydrogen and helium. Its volume is 755 times greater than that of Earth. Winds in the upper atmosphere reach 500 meters (1,600 feet) per second in the equatorial region. (In contrast, the strongest hurricane-force winds on Earth top out at about 110 meters, or 360 feet per second.) These super-fast winds, combined with heat rising from within the planet's interior, cause the yellow and gold bands visible in the atmosphere.

In the early 1980s, NASA's Voyager 1 and Voyager 2 spacecraft revealed that Saturn's rings are made mostly of water ice, and they imaged "braided" rings, ringlets, and "spokes" - dark features in the rings that circle the planet at different rates from that of the surrounding ring material. Saturn's ring system extends hundreds of thousands of kilometers from the planet, yet the vertical depth is typically about 10 meters (30 feet) in the main rings. During Saturn's equinox in autumn 2009, when sunlight illuminated the rings edge-on, Cassini spacecraft images showed vertical formations in some of the rings; the particles seem to pile up in bumps or ridges more than 3 kilometers (2 miles) tall.

Saturn's largest moon, Titan, is a bit bigger than the planet Mercury. (Titan is the second-largest moon in the solar system; only Jupiter's moon Ganymede is bigger.) Titan is shrouded in a thick, nitrogen-rich atmosphere that might be similar to what Earth's was like long ago. Further study of this moon promises to reveal much about planetary formation and, perhaps, about the early days of Earth. Saturn also has many smaller icy satellites. From Enceladus, which shows evidence of recent (and ongoing) surface changes, to Iapetus, with one hemisphere darker than asphalt and the other as bright as snow, each of Saturn's satellites is unique.

Though Saturn's magnetic field is not as huge as Jupiter's, it is still 578 times as powerful as Earth's. Saturn, the rings, and many of the satellites lie totally within Saturn's enormous mag-netosphere, the region of space in which the behavior of electrically charged particles is influenced more by Saturn's magnetic field than by the solar wind. While the Hubble Space Telescope imaged Saturn's aurora in the ultraviolet, the Cassini spacecraft found that Saturn has a unique secondary aurora at the north pole, imaged in the infrared by in 2008. Aurorae occur when charged particles spiral into a planet's atmosphere along magnetic field lines. On Earth, these charged particles come from the solar wind. Cassini showed that at least some of Saturn's aurorae are like Jupiter's and are largely unaffected by the solar wind.

The next chapter in our knowledge of Saturn is being written right now by the Cassini mission, which carried Europe's Huygens probe to Saturn. The Huygens probe descended through Titan's atmosphere in January 2005, collecting data on the atmosphere and surface. The Cassini spacecraft, orbiting Saturn since 2004, continues to explore the planet and its moons, rings, and magnetosphere. By July 2009, Cassini had returned more than 200,000 images. The Cassini Equinox Mission is studying the rings during Saturn's autumnal equinox, when the Sun shines directly on the equator and three-dimensional features such as moonlets that protrude above and below the ring plane cast shadows, revealing their sizes and shapes.

How Saturn Got its Name

Saturn is named for the Roman god of agriculture.

Saturn is the sixth planet from the sun in our solar system.

Second-largest planet in our solar system (Jupiter is the largest).

Saturn is about 97% Hydrogen gas, about 3% helium gas and about 0.05% methane, plus ammonia. Near the equator, tremendous winds blow at 1,100 mph (500 meters per second) toward the east. The clouds in the atmosphere are cold, thick and uniform in shape.

Saturn is a gaseous planet with a rocky core, a liquid metallic hydrogen layer above the core, and a molecular hydrogen layer above that. The hot, heavy, rocky core has a radius possibly three times the radius of the Earth.

Saturn has a strong magnetic field (less than Jupiter's, but still very strong). Probably generated by electrical current in conductive layers near the quickly-rotating planet's core. Because of this strong magnetic field, there are abundant auroras on Saturn and radios emissions from it.

Saturn radiates 79% more energy than it receives from the Sun, probably heat from its hot core.

Saturn is visible without using a telescope, but a low-power telescope is needed to see its rings. 

Saturn is about 74,898 miles (120,536 km) in diameter (at the equator at the cloud tops). This is about 9.4 times the diameter of the Earth. 764 Earths could fit inside a hollowed-out Saturn.

Saturn is the most oblate (flattened) planet in our Solar System. It has a equatorial diameter of 74,898 miles (120,536 km) (at the cloud tops) and a polar diameter of 67,560 miles (108,728 km). This is a difference of about 10%. Saturn's flattened shape is probably caused by its fast rotation and its gaseous composition.

RINGS
Saturn's beautiful rings are only visible from Earth using a telescope. They were first observed by Galileo in the 17th century.


Saturn's bright rings are made of ice chunks (and some rocks) that range in size from the size of a fingernail to the size of a car. Although the rings are extremely wide (over 1 million km in diameter), they are very thin (about 0.6 miles = 1 km thick). 

The rings are divided into 8 major ring divisions. There are two main sections (called rings A and B) plus the smaller ring (Ring C or the Crepe ring), D and F rings; the larger gap in the rings is called the Cassini division; the smaller one is the Encke division. Starting closest to Saturn, the rings and divisions are: D, C, B, The Cassini Division, A, the Encke division, and F (subdivided into G and E, and a ring with visible clumps of matter, called knots). A huge, distant eighth ring tilted 27 degrees from the planet's main ring plane was discovered in 2009.

Saturn's mass is about 5.69 x 10²⁶ kg. Although this is 95 times the mass of the Earth, the gravity on Saturn is only 1.08 times the gravity on Earth. A 100 pound person would only weigh 108 pounds on Saturn.

Saturn is the only planet in our Solar System that is less dense than water. Saturn would float if there were a body of water large enough!

Each day on Saturn takes 10.2 Earth hours. A year on Saturn takes 29.46 Earth years; it takes 29.46 Earth years for Saturn to orbit the sun once. 

At aphelion (the place in its orbit where Saturn is farthest from the Sun), Saturn is 1,503,000,000 km from the Sun. At perihelion (the place in its orbit where Saturn is closest to the Sun), Saturn is 1,348,000,000 km from the Sun.

The mean temperature on Saturn (at the cloud tops) is 88 K (-185° C; -290° F).

Saturn has dozens of moons (33 discovered as of August, 2004). It has 18 named moons. including Titan (the largest), Rhea, Iapetus, Dione, Tethys, Enceladus, Mimas, Hyperion, Phoebe, Janus, Epimetheus, Pandora, Prometheus, Helene, Telesto, Atlas, Calypso, and Pan (the smallest named moon of Saturn). At least a dozen others have been noted (but not named yet).

Saturn has been visited by Pioneer 11 (in 1979) and by Voyager 1 and Voyager 2. Cassini, a spacecraft named for the divisions in Saturn's rings, is on the way and will arrive in 2004.

Saturn was named for the Roman god of agriculture.