Saturn is the sixth planet from the Sun.
Saturn was named after the Roman god Saturnus, (called Cronos in Greek mythology). Saturn's symbol is ♄ which is the symbol of Saturnus' sickle. Saturn is the second largest planet in the Solar System; the largest is Jupiter. Like Jupiter, Uranus and Neptune, Saturn is made mostly of gas and does not have a solid surface. Because of this, these four planets are called "gas giants".
Saturn has 61 moons, (plus 3 others that are not confirmed yet as of 2009). The largest moon is Titan, which is larger than the planet Mercury. Also around Saturn there is a very large system of rings, made of ice with smaller amounts of rocks and dust. Saturn is about 1.4 billion km from the Sun. It takes 29.5 Earth years to orbit around the Sun.
Saturn is an oblate spheroid, meaning that it is flattened at the poles, and it swells out around its equator. The planet's equatorial diameter is 120,536 km (74,867 mi) whereas its polar diameter (i.e. from the north pole to the south pole) is 108,728 km (67,535 mi); a 9% difference. Its flattened shape is due to its very fast rotation, rotating once every 10.8 Earth hours. Saturn is the only planet in the Solar System that is less dense than water. Even though the planet's core is very dense, it has a gaseous atmosphere, so the average specific density of the planet is 0.69 g/cm³ (less than water). As a result, if Saturn were placed in a large pool of water, it would float on it.
The outer part of Saturn's atmosphere is made up of 96.7% hydrogen, 3% helium, 0.2% methane and 0.02% ammonia. There are also very small amounts of acetylene, ethane and phosphine.
Saturn's interior is similar to Jupiter's interior. It has a small rocky core at its centre and it is very hot; its temperature reaches 15,000 K (26,540 °F, 14,730 °C). It is so hot that it radiates about two and a half times more heat energy into space than the amount of energy Saturn receives from the Sun. The core is about the same size as the Earth's, but more dense. Above it is a thicker layer of metallic hydrogen, about 30,000 km (18,600 mi) deep. Above that layer is a region of liquid hydrogen and helium. The core is heavy, about 9 to 22 times more mass than the Earth's core.
Saturn has a natural magnetic field that is much weaker than Jupiter's. Like the Earth's, Saturn's field is a magnetic dipole. Saturn's field is unique in that it is perfectly symmetrical, unlike any other known planet (ie. the field is exactly in line with the planet's axis). Saturn generates radio waves, but they are too weak to be detected from Earth. The moon Titan orbits in the outer part of Saturn's magnetic field and gives out plasma to the field from the ionised particles in Titan's atmosphere.
Saturn's average distance from the Sun is over 1.4 billion km, about 9 times is distance from the Earth to the Sun. It takes 29.5 Earth years for Saturn to orbit around the Sun. This is known as Saturn's orbital period. Saturn takes about 10.8 Earth hours to rotate around its axis. This is known as its rotational period. It is known that its rotational period does not stay the same, therefore, Saturn does not rotate at a constant rate. Its rotational period is determined by the rotation speed of the radio waves released by the planet. The Cassini-Huygens spacecraft discovered that the radio emissions slowed down, thus the rotational period increased. It is unknown what caused the radio waves to slow down.
Saturn is best known for its planetary rings which are easy to see with a telescope. The rings make Saturn one of the most interesting things to see in the night sky. The rings were first discovered by Galileo Galilei in 1610, using his telescope. Actually they did not look like rings to Galileo, so he called them "ears". He stated that Saturn was actually three separate planets that almost touch one another. In 1612, when the rings were facing edge on with the Earth, the rings disappeared, then reappeared again in 1613, further confusing Galileo. In 1655, Christiaan Huygens was the first person who suggested that Saturn was surrounded by rings. He observed Saturn using a much more powerful telescope than Galilei's. He quoted that "It [Saturn] is surrounded by a thin, flat, ring, nowhere touching, inclined to the ecliptic."In 1675, Giovanni Domenico Cassini discovered that the planet's rings were in fact made of smaller ringlets with gaps. The largest ring gap was later named the Cassini Division. In 1859, James Clerk Maxwell showed that the rings cannot be solid, but are made of small particles, each orbiting Saturn on their own, otherwise, it would become unstable or break apart. James Keeler studied the rings using a spectroscope in 1895 which proved Maxwell's theory to be correct.
The rings range from 6,630 km to 120,700 km above the planet's equator. As proved by Maxwell, even though the rings appear to be solid and unbroken when viewed from above, the rings are made of small particles of rock and ice. The rings are on average up to one kilometre thick and are made of silica rock, iron oxide and ice particles. The smallest particles are only specks of dust while the largest are the size of a house.
The Voyager space probe discovered features shaped like rays, called spokes. They are seen as dark when under sunlight, and appear light when against the unlit side. It is assumed that the spokes are made of microscopic dust particles that are raised above the ring plane. They rotate at the same time with the planet's magnetosphere, therefore, it is assumed that they have a connection with electromagnetism. However, the exact reason explaining why these spokes exist is still unknown.
Saturn has at least 60 moons, 48 of these have names. Many of the moons are very small: 33 of the 50 moons are less than 10 km in diameter and a further 13 moons are less than 50 km. Seven moons are large enough to be a near perfect sphere caused by their own gravitation. These moons are Titan, Rhea, Iapetus, Dione, Tethys, Enceladus and Mimas. Titan is the largest moon, larger than the planet Mercury, and it is the only moon in the Solar System to have a thick, dense atmosphere. Hyperion and Phoebe are the next largest moons, larger than 200 km in diameter.
Saturn was first explored by the Pioneer 11 spacecraft on September 1979. It flew as close as 20,000 km above the planet's cloud tops. It took photographs of the planet and a few of its moons, but were low in resolution (the quality was not very good). It discovered a new, thin ring called the F ring, and discovered that the dark ring gaps appear bright when viewed towards the Sun, indicating the gaps are not empty of material. The spacecraft meaured the temperature of the moon Titan.
On November 1980, Voyager 1 visited Saturn, and took higher resolution photographs of the planet, rings and moons. Unlike Pioneer 11, the images were good enough to focus on the surface features of the moons. Voyager 1 made a close encounter of Titan, and gained much information about its atmosphere. In August, 1981, Voyager 2 continued to study the planet. Images taken by the space probe indicated that changes were happening to the rings and atmosphere. The Voyager spacecrafts discovered a number of moons orbiting close to Saturn's rings, as well as discovering new ring gaps.
On July 1, 2004, the Cassini-Huygens probe entered into orbit around Saturn. Before then, it made a close flyby of Phoebe, taking very high resolution images of its surface and gaining high amounts of data. On December 25, 2004, the Huygens probe separated from the Cassini probe before moving down towards Titan's surface and landed there on January 14, 2005. It landed on a dry surface, but it confirmed that large bodies of liquid exist on the moon. The Cassini probe continued to gain data of Titan and a number of the icy moons. It found evidence that the moon Enceladus had water erupting from its geysers. Cassini also proved in July 2006 that Titan contained hydrocarbon lakes, located near its north pole. In March 2007, it discovered a large hydrocarbon lake the size of the Caspian Sea near its north pole.
Topics of Interest
The magnetosphere of Saturn is the cavity created in the flow of the solar wind by the planet's internally generated magnetic field. Discovered in 1979 by the Pioneer 11 spacecraft, Saturn's magnetosphere is the second largest of any planet in the Solar System after Jupiter.
The rings of Saturn are the most extensive planetary ring system of any planet in the Solar System. They consist of countless small particles, ranging in size from micrometres to metres, that form clumps that in turn orbit about Saturn. The ring particles are made almost entirely of water ice, with some contamination from dust and other chemicals.
The moons of Saturn are numerous and diverse, ranging from tiny moonlets to the enormous Titan. Saturn has 61 moons with confirmed orbits, 53 of which have names, and most of which are quite small. There are also hundreds of known moonlets embedded within Saturn's rings. With seven moons that are large enough to have sufficient gravitational attraction to become spherical in shape (and which would thus be considered dwarf planets if they were in direct orbit about the Sun) in addition to the planet's broad and dense rings, the Saturnian system is the most diverse in the solar system. Particularly notable are Titan, the second largest moon in the Solar System, with an earth-like atmosphere and a landscape including hydrocarbon lakes and river networks, and Enceladus, which may harbor liquid water under its south pole.
Saturn (Latin: Saturnus) was a major Roman god of agriculture and harvest. In medieval times he was known as the Roman god of agriculture, justice and strength; he held a sickle in his left hand and a bundle of wheat in his right. His mother's name was Helen, or Hel. He was identified in classical antiquity with the Greek deity Cronus, and the mythologies of the two gods are commonly mixed. Saturn's wife was Ops (the Roman equivalent of Rhea). Saturn was the father of Ceres, Jupiter, Veritas, Pluto, and Neptune, among others. Saturn had a temple on the Forum Romanum which contained the Royal Treasury. Saturn is the namesake of both Saturn, the planet, and Saturday (dies Saturni).
Saturn in astrology is the ruling planet of Capricorn and, traditionally, Aquarius and is exalted in Libra. In Roman mythology Saturn is the god of agriculture, founder of civilizations and of social order and conformity. The glyph is most often seen as scythe-like but it is primarily known as the "crescent below the cross", whereas Jupiter's glyph is the "crescent above the cross". The famous rings of the planet Saturn that enclose and surround it, reflect this principle of man's limitations. Saturn takes 29.5 years to orbit the sun, spending about 2.46 years in each sign of the zodiac.
Astrologically Saturn is associated with the principles of limitation, restrictions, boundaries, practicality and reality, crystallizing and structures. Saturn governs ambition, career, authority and hierarchy, and conforming social structures. It concerns a person's sense of duty, discipline and responsibility, and their physical and emotional endurance during hardships. Saturn is also considered to represent the part of a person concerned with long-term planning. The Return of Saturn is said to mark significant events in each person's life. According to the first-century poet Manilius, Saturn is sad, morose, and cold and is the greater malefic. According to Claudius Ptolemy, "Saturn is lord of the right ear, the spleen, the bladder, the phlegm, and the bones."Saturn symbolized processes and things which were dry and extremely cold, and, therefore, inimical to life. It governed the melancholic humor.
The planet Saturn is featured in numerous science fiction novels and films, although the planet itself usually serves more as a pretty backdrop than as the actual setting.
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