Tuesday, April 8, 2014

Saturn

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Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Named after the Roman god of agriculture, its astronomical symbol (♄) represents the god's sickle. Saturn is a gas giant with an average radius about nine times that of Earth. While only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive.
Saturn's interior is probably composed of a core of iron, nickel and rock (silicon and oxygen compounds), surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium and an outer gaseous layer. The planet exhibits a pale yellow hue due to ammonia crystals in its upper atmosphere. Electrical current within the metallic hydrogen layer is thought to give rise to Saturn's planetary magnetic field, which is weaker than Earth's magnetic field but has a magnetic moment 580 times that of the Earth due to Saturn's larger body radius. Saturn's magnetic field strength is around one-twentieth the strength of Jupiter's. The outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h (1,100 mph), faster than on Jupiter, but not as fast as those on Neptune.
Saturn has a prominent ring system that consists of nine continuous main rings and three discontinuous arcs, composed mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-two known moons orbit the planet; fifty-three are officially named. This does not include the hundreds of "moonlets" comprising the rings. Titan, Saturn's largest and the Solar System's second largest moon, is larger than the planet Mercury and is the only moon in the Solar System to retain a substantial atmosphere.
Saturn is the sixth planet from the sun and the second largest planet in the solar system. Although the other gas giants in the solar system — Jupiter, Uranus and Neptune — also have rings, those of Saturn are without a doubt the most extraordinary.
Saturn was the Roman name for Cronus, the lord of the Titans in Greek mythology. Saturn is the root of the English word "Saturday."

Physical characteristics of Saturn

Saturn is a gas giant made up mostly of hydrogen and helium. Saturn is bigenough to hold more than 760 Earths, and is more massive than any other planet except Jupiter, roughly 95 times Earth's mass. However, Saturn has the lowest density of all the planets, and is the only one less dense than water — if there were a bathtub big enough to hold it, Saturn would float.
Saturn is the farthest planet from Earth visible to the naked human eye. The yellow and gold bands seen in Saturn's atmosphere are the result of super-fast winds in the upper atmosphere, which can reach up to 1,100 mph (1,800 kph) around its equator, combined with heat rising from the planet's interior.
Saturn spins faster than any other planet except Jupiter, completing a rotation roughly every 10-and-a-half hours. This rapid spinning causes Saturn to bulge at its equator and flatten at its poles — the planet is 8,000 miles (13,000 km) wider at its equator than between the poles.
Saturn's most recent curiosity may be the giant hexagon circling its north pole, with each of its sides nearly 7,500 miles (12,500 km) across — big enough to fit nearly four Earths inside. Thermal images show it reaches some 60 miles (100 km) down into the planet's atmosphere. It remains uncertain what causes it.

Composition & structure

Atmospheric composition (by volume)
96.3 percent molecular hydrogen, 3.25 percent helium, minor amounts of methane, ammonia, hydrogen deuteride, ethane, ammonia ice aerosols, water ice aerosols, ammonia hydrosulfide aerosols
Magnetic field
Saturn has a magnetic field about 578 times more powerful than Earth's.
Chemical composition
Saturn seems to have a hot solid inner core of iron and rocky material surrounded by an outer core probably composed of ammonia, methane, and water. Next is a layer of highly compressed, liquid metallic hydrogen, followed by a region of viscous hydrogen and helium. This hydrogen and helium becomes gaseous near the planet's surface and merges with its atmosphere.
Internal structure
Saturn seems to have a core between about 10 to 20 times as massive as the Earth.

Orbit & rotation

Average distance from the sun: 885,904,700 miles (1,426,725,400 km)
By Comparison: 9.53707 times that of Earth
Perihelion (closest approach to sun): 838,519,000 miles (1,349,467,000 km)
By Comparison: 9.177 times that of Earth
Aphelion (farthest distance from sun): 934,530,000 miles (1,503,983,000 km)
By Comparison: 9.886 times that of Earth

Saturn's moons

Saturn has at least 62 moons. Since the planet was named after Cronus, lord of the Titans in Greek mythology, most of Saturn's moons are named after other Titans, their descendants, as well as after giants from Gallic, Inuit and Norse myths.
Saturn's largest moon, Titan, is slightly larger than Mercury, and is the second-largest moon in the solar system behind Jupiter's moon Ganymede. Titan is veiled under a very thick, nitrogen-rich atmosphere that might be like what Earth's was long ago, before life. While the Earth's atmosphere extends only about 37 miles (60 km) into space, Titan's reaches nearly 10 times as far. These moons can possess bizarre features. Pan and Atlas are shaped like flying saucers, Iapetus has one side as bright as snow and one side as dark as coal, and Enceladus shows evidence of "ice volcanism," spewing out water and other chemicals. A number of these satellites, such as Prometheus and Pandora, are shepherd moons, interacting with ring material to keep rings in their orbits.

Saturn's rings

Galileo Galilei was the first to see Saturn's rings in 1610, although from his telescope they resembled handles or arms. It took Dutch astronomer Christiaan Huygens, who had a more powerful telescope, to propose that Saturn had a thin, flat ring. Saturn actually has many rings made of billions of particles of ice and rock, ranging in size from a grain of sugar to the size of a house. The largest ring spans up to 200 times the diameter of the planet. The rings are believe to be debris left over from comets, asteroids or shattered moons. Although they extend thousands of miles from the planet, the main rings are typically only about 30 feet thick. The Cassini-Huygens spacecraft revealed vertical formations in some of the rings, with particles piling up in bumps and ridges more than 2 miles (3 km) high. The rings are generally named alphabetically in the order they were discovered. They are usually relatively close to each other, with one key exception caused by the Cassini Division, a gap some 2,920 miles (4,700 km) wide. The main rings, working out from the planet, are known as C, B and A, with the Cassini Division separating B and A. The innermost is the extremely faint D ring, while the outermost to date, revealed in 2009, could fit a billion Earths within it. Mysterious spokes have been seen in Saturn's rings, which might form and disperse over a few hours. Scientists have conjectured these spokes might be composed of electrically charged sheets of dust-sized particles created by small meteors impacting the rings or electron beams from the planet's lightning. Saturn's F Ring also has a curious braided appearance — it is composed of several narrow rings, and bends, kinks, and bright clumps in them can give the illusion that these strands are braided.

Research & exploration

The first spacecraft to reach Saturn was Pioneer 11 in 1979, flying within 13,700 miles (22,000 km) of it, which discovered the planet's two of its outer rings as well as the presence of a strong magnetic field. The Voyager spacecraft discovered the planet's rings are made up of ringlets, and sent back data that led to the discovery or confirmation of the existence of nine moons.
The Cassini spacecraft now in orbit around Saturn is the largest interplanetary spacecraft ever built, a two-story-tall probe that, at 6 tons in weight (5,650 kilograms), is roughly equal in mass to an empty 30-passenger school bus. It discovered plumes on the icy moon Enceladus, and carried the Huygens probe, which plunged through Titan's atmosphere to successfully land on its surface.

Saturn's gravitational impact on the solar system

As the most massive planet in the solar system after Jupiter, the pull of Saturn's gravity has helped shape the fate of our system. It may have helped violently hurl Neptune and Uranus outward. It, along with Jupiter, might also have slung a barrage of debris toward the inner planets early in the system's history.

Saturn's surface

Saturn is classified as a gas giant because it is almost completely made of gas. Its atmosphere bleeds into its "surface" with little distinction. If a spacecraft attempted to touch down on Saturn, it would never find solid ground. Of course, the craft would be fortunate to survive long before the increasing pressure of the planet crushed it. Because Saturn lacks a traditional ground, scientists consider the surface of the planet to begin when the pressure exceeds one bar, the approximate pressure at sea level on Earth

Saturn's interior

At higher pressures, below the determined surface, hydrogen on Saturn becomes liquid. Traveling inward toward the center of the planet, the increased pressure causes the liquefied gas to become metallic hydrogen. Saturn does not have as much metallic hydrogen as the largest planet, Jupiter, but it does contain more ices. Saturn is also significantly less dense than any other planet in the solar system; in a large enough pool of water, the ringed planet would float. Like Jupiter, Saturn is suspected to have a rocky core surrounded by hydrogen and helium. However, the question of how solid the core might be is still up for debate. Though composed of rocky material, the core itself may be liquid. The distance to Saturn from the sun is significant, keeping the average temperature of Saturn low, but things are hotter within the rocky core. There, temperatures can reach as high as 21,000 degrees Fahrenheit (11,700 degrees Celsius). During the formation of Saturn, the core would have been created first. Research suggests that Saturn's rocky core is between 9 to 22 times the mass of Earth. Only when it reached sufficient mass would the planet have been able to gravitationally pile on the light hydrogen and helium gas that make up most of the its mass.

A strong magnetic field

As on Jupiter, the liquid metallic hydrogen drives the magnetic field of Saturn. Saturn's magnetosphere is smaller than its giant sibling, but still significantly more powerful than those found on the terrestrial planets. With a magnetosphere large enough to contain the entire planet and its rings, Saturn's magnetic field is 578 times as powerful as Earth's.

The rings of Saturn

When Italian astronomer Galileo Galilei turned his telescope toward Saturn, he observed two blobs on either side that he identified as bodies separate from the main planet. It wasn't until Dutch astronomer Christiaan Huygens studied the planet with a more powerful scope that the rings of Saturn were first identified. Although most of the gas giants boast rings of some sort, Saturn's are the largest and arguably the most visually stunning. Stretching as far out as 262,670 miles (422,730 km), or eight times the radius of the planet, the rings are made up of ice and rock pieces that create a rainbow effect as they refract the light from the sun.

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