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Interior of Saturn with several cool characteristics of the ringed gigantic planet.

Saturn is the sixth planet in the Solar System, as well as the second (largest) gas planet. Saturn is mostly known for its rings, the largest in the Solar System. Mysterious spokes have been seen in Saturn's rings, which appear to form and disperse within only a few hours. Every single gas planet has rings but Jupiter's and Neptune's rings are very faint. Saturn is a gas giant with a maximum equatorial radius of about nine point four hundred fifty nine (9.459) times that of Earth. It only has one-eighth the average density of Earth and it's density is 0,69 times that of water. Saturn would float on water if we had a big enough ocean. However, with its large volume, Saturn is about 95.54 times more massive than Earth. Saturn is named after the Roman god of wealth and agriculture; its astronomical symbol (♄) represents the god's sickle. The Romans named the seventh day of the week Saturday, Sāturni diēs ("Saturn's Day") no later than the 2nd century for the planet Saturn.

Saturn is mostly hydrogen and helium like Jupiter. While Jupiter is larger, denser and about 3 times more massive, Saturn has 3 more Moons (82 of Saturn vs 79 of Jupiter), much larger white spots (similar to Jupiter's red spot) and definitely larger, thicker, denser, brighter and wider rings. Being the second largest planet, also larger than many brown dwarf stars that are not considered real stars, but sub-stars, Saturn is even larger than EBLM-j0555-57Ab, the smallest star ever discovered, a red dwarf star, about 600 light years away. Saying that Saturn is even larger than a star, Saturn is so large, that it can fit 764 times our planet Earth inside it.

Saturn has a polar diameter of 108.728 km, a main diameter of 116.464 km and a equatorial diameter of 120.536 km, nearly 9.459 times the diameter of Earth. Since Saturn was discovered, it was long thought to be the farthest planet in the Solar System, but that changed in 1781 when William Hershel discovered Uranus. Saturn is also the last planet discovered with the naked eye, discovered around 1600, and was firstly considered a star. The gravity of Saturn is 10.44 m/s².

The most beautiful planet

Saturn vs Earth in Size

Composition

Cloud layers

Saturn's atmosphere exhibits a banded pattern similar to Jupiter's, but Saturn's bands are much fainter and are much wider near the equator. The nomenclature used to describe these bands is the same as on Jupiter. Saturn's finer cloud patterns were not observed until the flybys of the Voyager spacecraft during the 1980s. Since then, Earth-based telescopy has improved to the point where regular observations can be made. The composition of the clouds varies with depth and increasing pressure. In the upper cloud layers, with the temperature in the range 100–160 K and pressures extending between 0.5–2 bar, the clouds consist of ammonia ice. Water ice clouds begin at a level where the pressure is about 2.5 bar and extend down to 9.5 bar, where temperatures range from 185 to 270 K. Intermixed in this layer is a band of ammonium hydrosulfide ice, lying in the pressure range 3–6 bar with temperatures of 190–235 K. Finally, the lower layers, where pressures are between 10 and 20 bar and temperatures are 270–330 K, contains a region of water droplets with ammonia in aqueous solution.

Saturn's usually bland atmosphere occasionally exhibits long-lived ovals and other features common on Jupiter. In 1990, the Hubble Space Telescope imaged an enormous white cloud near Saturn's equator that was not present during the Voyager encounters, and in 1994 another smaller storm was observed. The 1990 storm was an example of a Great White Spot, a unique but short-lived phenomenon that occurs once every Saturnian year, roughly every 30 Earth years, around the time of the northern hemisphere's summer solstice. Previous Great White Spots were observed in 1876, 1903, 1933 and 1960, with the 1933 storm being the most famous. If the periodicity is maintained, another storm will occur in about 2020. The winds on Saturn are the second fastest among the Solar System's planets, after Neptune's. Voyager data indicate peak easterly winds of 500 m/s (1,800 km/h). In images from the Cassini spacecraft during 2007, Saturn's northern hemisphere displayed a bright blue hue, similar to Uranus. The color was most likely caused by Rayleigh scattering. Thermography has shown that Saturn's south pole has a warm polar vortex, the only known example of such a phenomenon in the Solar System. Whereas temperatures on Saturn are normally −185 °C, temperatures on the vortex often reach as high as −122 °C, suspected to be the warmest spot on Saturn.

Atmosphere

Saturn's atmosphere is similar to Jupiter's; majority (75%) hydrogen, minority (24%) helium, methane, ice and others fill the rest. However, even though it is similar, Saturn lacks the necessary elements to form such brightly colored bands, it replaces this with sulphur, nitrogen and oxygen, into molecules like smog. Saturn does not lack these bands, but they are much less visibly present.[1] The layer we can see, the upper cloud deck, has ammonia rich clouds that lay 100 km below the tropopause. Here, temperatures can a staggering -250 °C. The lower cloud deck, 170 km below the tropopause, is made out of ammonium hydrosulfide clouds, with temperatures of -70 °C. The lowest cloud deck has water clouds, at temperatures of 0 °C.[2]

Saturn's atmosphere exhibits a banded pattern similar to Jupiter's, but Saturn's bands are much fainter and are much wider near the equator. The nomenclature used to describe these bands is the same as on Jupiter. Saturn's finer cloud patterns were not observed until the flybys of the Voyager spacecraft during the 1980s. Since then, Earth-based telescopy has improved to the point where regular observations can be made.

The composition of the clouds varies with depth and increasing pressure. In the upper cloud layers, with the temperature in the range 100–160 K and pressures extending between 0.5–2 bar, the clouds consist of ammonia ice. Water ice clouds begin at a level where the pressure is about 2.5 bar and extend down to 9.5 bar, where temperatures range from 185 to 270 K. Intermixed in this layer is a band of ammonium hydrosulfide ice, lying in the pressure range 3–6 bar with temperatures of 190–235 K. Finally, the lower layers, where pressures are between 10 and 20 bar and temperatures are 270–330 K, contains a region of water droplets with ammonia in aqueous solution.

The winds on Saturn are the second fastest among the Solar System's planets, after Neptune's. Voyager data indicate peak easterly winds of 500 m/s (1,800 km/h). In images from the Cassini spacecraft during 2007, Saturn's northern hemisphere displayed a bright blue hue, similar to Uranus. The color was most likely caused by Rayleigh scattering. Thermography has shown that Saturn's south pole has a warm polar vortex, the only known example of such a phenomenon in the Solar System. Whereas temperatures on Saturn are normally −185 °C, temperatures on the vortex often reach as high as −122 °C, suspected to be the warmest spot on Saturn.

Diagram of Saturn ( to scale )

Saturn is slightly larger than EBLM J0555-57Ab. The star has a maximum diameter of 118.000 km while Saturn has a maximum diameter of 120.536 km.

Interior

Despite consisting mostly of hydrogen and helium, most of Saturn's mass is not in the gas phase, because hydrogen becomes a non-ideal liquid when the density is above 0.01 g/cm3, which is reached at a radius containing 99.9% of Saturn's mass. The temperature, pressure, and density inside Saturn all rise steadily toward the core, which causes hydrogen to be a metal in the deeper layers.

Standard planetary models suggest that the interior of Saturn is similar to that of Jupiter, having a small rocky core surrounded by hydrogen and helium, with trace amounts of various volatiles. This core is similar in composition to Earth, but is more dense. The examination of Saturn's gravitational moment, in combination with physical models of the interior, has allowed constraints to be placed on the mass of Saturn's core. In 2004, scientists estimated that the core must be 9–22 times the mass of Earth, which corresponds to a diameter of about 25,000 km. This is surrounded by a thicker liquid metallic hydrogen layer, followed by a liquid layer of helium-saturated molecular hydrogen that gradually transitions to a gas with increasing altitude. The outermost layer spans 1,000 km and consists of gas.

Saturn has a hot interior, reaching 11,700 °C at its core, and radiates 2.5 times more energy into space than it receives from the Sun. Saturn's interior is most likely composed of a core of iron–nickel and rock (silicon and oxygen compounds). Its core is surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium, and finally a gaseous outer layer. Saturn has a pale yellow hue due to ammonia crystals in its upper atmosphere. An electrical current within the metallic hydrogen layer is thought to give rise to Saturn's planetary magnetic field, which is weaker than the Earth's, but which has a magnetic moment 580 times that of Earth due to Saturn's larger size. Saturn's magnetic field strength is around one-twentieth 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; 500 m/s), higher than on Jupiter but not as high as on Neptune. In January 2019, astronomers reported that a day on the planet Saturn has been determined to be 10h 33m 38s + 1m 52s− 1m 19s , based on studies of the planet's C Ring.

As it turns out, Saturn is even more alike to Jupiter. Due to the immense pressures and temperatures, at a certain level deep into Saturn, the hydrogen becomes liquid, then metallic at the core. [3]During the formation of Saturn, the core would have been made first, then, when it reaches the mass of around 30 earths, would it finally be able to attract gasses to form a planet. [4]

Saturn's creasing pressure. In the upper cloud layers, with the temperature in the range 100–160 K and pressures extending between 0.5–2 bar, the clouds consist of ammonia ice. Water ice clouds begin at a level where the pressure is about 2.5 bar and extend down to 9.5 bar, where temperatures range from 185 to 270 K. Intermixed in this layer is a band of ammonium hydrosulfide ice, lying in the pressure range 3–6 bar with temperatures of 190–235 K. Finally, the lower layers, where pressures are between 10 and 20 bar and temperatures are 270–330 K, contains a region of water droplets with ammonia in aqueous solution. Saturn's usually bland atmosphere occasionally exhibits long-lived ovals and other features common on Jupiter. In 1990, the Hubble Space Telescope imaged an enormous white cloud near Saturn's equator that was not present during the Voyager encounters, and in 1994 another smaller storm was observed. The 1990 storm was an example of a Great White Spot, a unique but short-lived phenomenon that occurs once every Saturnian year, roughly every 30 Earth years, around the time of the northern hemisphere's summer solstice. Previous Great White Spots were observed in 1876, 1903, 1933 and 1960, with the 1933 storm being the most famous. If the periodicity is maintained, another storm will occur in about 2020.

The winds on Saturn are the second fastest among the Solar System's planets, after Neptune's. Voyager data indicate peak easterly winds of 500 m/s (1,800 km/h). In images from the Cassini spacecraft during 2007, Saturn's northern hemisphere displayed a bright blue hue, similar to Uranus. The color was most likely caused by Rayleigh scattering. Thermography has shown that Saturn's south pole has a warm polar vortex, the only known example of such a phenomenon in the Solar System. Whereas temperatures on Saturn are normally −185 °C, temperatures on the vortex often reach as high as −122 °C, suspected to be the warmest spot on Saturn.

Magnetosphere

The structure of Saturn's magnetosphere.

Saturn has an intrinsic magnetic field that has a simple, symmetric shape – a magnetic dipole. Its strength at the equator – 0.2 gauss (20 µT) – is approximately one twentieth of that of the field around Jupiter and slightly weaker than Earth's magnetic field. As a result, Saturn's magnetosphere is much smaller than Jupiter's. When Voyager 2 entered the magnetosphere, the solar wind pressure was high and the magnetosphere extended only 19 Saturn radii, or 1.1 million km (712,000 mi), although it enlarged within several hours, and remained so for about three days. Most probably, the magnetic field is generated similarly to that of Jupiter – by currents in the liquid metallic-hydrogen layer called a metallic-hydrogen dynamo. This magnetosphere is efficient at deflecting the solar wind particles from the Sun. The moon Titan orbits within the outer part of Saturn's magnetosphere and contributes plasma from the ionized particles in Titan's outer atmosphere. Saturn's magnetosphere, like Earth's, produces aurora.

Saturn's magnetosphere is filled with plasma originating from both the planet and its moons. The main source is the small moon Enceladus, which ejects as much as 1,000 kg/s of water vapor from the geysers on its south pole, a portion of which is ionized and forced to co-rotate with the Saturn’s magnetic field. This loads the field with as much as 100 kg of water group ions per second. This plasma gradually moves out from the inner magnetosphere via the interchange instability mechanism and then escapes through the magnetail.

The interaction between Saturn's magnetosphere and the solar wind generates bright oval aurora around the planet's poles observed in visible, infrared and ultraviolet light. The aurora are related to the powerful saturnian kilo-metric radiation (SKR), which spans the frequency interval between 100 kHz to 1300 kHz and was once thought to modulate with a period equal to the planet's rotation. However, later measurements showed that the periodicity of the SKR's modulation varies by as much as 1%, and so probably does not exactly coincide with Saturn’s true rotational period, which as of 2010 remains unknown. Inside the magnetosphere there are radiation belts, which house particles with energy as high as tens of megaleactronvolts. The energetic particles have significant influence on the surfaces of inner icy moons of Saturn. In 1980–1981 the magnetosphere of Saturn was studied by the Voyager spacecraft. Up until September 2017 it was a subject of ongoing investigation by Cassini mission, which arrived in 2004 and spent over 15 years observing the planet.

Great white Spot(s)

Saturn's Great White Spot in 2011.

The Great White Spot, also known as Great White Oval, on Saturn, named by analogy to Jupiter's Great Red Spot, are periodic storms that are large enough to be visible from Earth by telescope by their characteristic white appearance. The spots can be several thousands of kilometers wide. The Cassini orbiter was able to track the 2010–11 instance of the storm, also known as the Northern Electrostatic Disturbance because of an increase in radio and plasma interference, or the Great Springtime Storm. Cassini data has revealed a loss of acetylene in the white clouds, an increase of phosphine, and an unusual temperature drop in the center of the storm. After the visible aspects of the storm subsided, in 2012, a "belch" of heat and ethylene was emitted from two hotspots that merged.

The storm in December 2010.

The Great White Spot typically begins as discrete "spots", but then rapidly expands in longitude, as the 1933 and 1990 GWSs did; in fact, the latter eventually lengthened enough to encircle the planet. Though computer modeling had by the early 1990s suggested these massive atmospheric upwellings were caused by thermal instability, in 2015 two Caltech planetary scientists proposed a more detailed mechanism. The theory is that as Saturn's upper atmosphere undergoes seasonal cooling, it first gets less dense as the heavier water rains out, passes a density minimum, and then gets more dense as the remaining hydrogen and helium continue to cool. Low-density upper-layer gases tend to suppress convection, but high-density upper layers are unstable and cause a thunderstorm when they break into lower layers. The theory is that the storms are significantly delayed from the winter solstice due to the time it takes for the very large atmosphere to cool. The team proposes that similar storms are not seen on Jupiter because that planet has less water vapor in its upper atmosphere.

Saturn's rings block the view of the northern hemisphere from Earth during the winter solstice, so historical data on the GWS is unavailable during this season, but the Cassini space probe has been able to observe the whole planet since it arrived shortly after the winter solstice in 2004.

Rings

Saturn's rings with moons illustrated in

Saturn is probably best known for the system of planetary rings that makes it visually unique. The rings extend from 6,630 to 120,700 kilometers (4,120 to 75,000 mi) outward from Saturn's equator and average approximately 20 meters (66 ft) in thickness. They are composed predominantly of water ice, with trace amounts of tholin impurities and a peppered coating of approximately 7% amorphous carbon. The particles that make up the rings range in size from specks of dust up to 10 m. While the other gas giants also have ring systems, Saturn's is the largest, widest, densest, thickest, brightest, most massive and most visible. Saturn's rings can be seen with a simple telescope and it is not hard at all to see them. Generally, theories about how the rings were formed have to do with a moon of Saturn that was destroyed, and probably not too long ago, at around 100 million years before.

Galileo Galilei was the first to observe the rings of Saturn in 1610 using his telescope, but was unable to identify them as such. He wrote to the Duke of Tuscany that "The planet Saturn is not alone, but is composed of three, which almost touch one another and never move nor change with respect to one another. They are arranged in a line parallel to the zodiac, and the middle one (Saturn itself) is about three times the size of the lateral ones." He also described the rings as Saturn's "ears". In 1612 the Earth passed through the plane of the rings and they became invisible. Mystified, Galileo remarked "I do not know what to say in a case so surprising, so unlooked for and so novel." He mused, "Has Saturn swallowed his children?" — referring to the myth of the Titan Saturn devouring his offspring to forestall the prophecy of them overthrowing him. He was further confused when the rings again became visible in 1613.

There are two main hypotheses regarding the origin of the rings. One hypothesis is that the rings are remnants of a destroyed moon of Saturn. The second hypothesis is that the rings are left over from the original nebular material from which Saturn was formed. Some ice in the E ring comes from the moon Enceladus's geysers. The water abundance of the rings varies radially, with the outermost ring A being the most pure in ice water. This abundance variance may be explained by meteor bombardment.

Saturn's rings are divided into the A, B, C, D, E, F and G rings, as well as other moon-specific rings. The rings range from being a few thousand km away from Saturn, to being millions of km away, like the Phoebe ring, which is 13,000,000 km away and is tilted at an angle of 27° to the other rings and orbits in retrograde fashion. Some of the moons of Saturn, including Pandora and Prometheus, act as shepherd moons to confine the rings and prevent them from spreading out. Pan and Atlas cause weak, linear density waves in Saturn's rings that have yielded more reliable calculations of their masses The rings are further divided into ringlets, of which there can be hundreds. The rings aren't thin either, some are just meters thin, but some are a few kilometers. The spaces between rings are named after real people, these gaps can go form 400 km to 3 km in wide. Inside of these rings are many moons and moonlets, they are formed by collisions and further collisions due to previous collisions, ice, dust and rocks pilling up to form moons over millions of years is one of the reasons why such gaps in the rings occur. [5]The rings, as mentioned above, are made primarily out of ice, dust, rocks, asteroid debris, collision debris and other universal scrap. These clumps of materials can be microscopic or meters tall. [6]

Moons

Moons and Rings of Saturn

Many Moons of Saturn

Saturn has the most Moons of all the planets, 82, 3 more than Jupiter's 79. The moons of Saturn are numerous and diverse, ranging from tiny moon-lets only tens of meters across to enormous Titan, which is larger than the planet Mercury. Saturn has 82 moons with confirmed orbits that are not embedded in its rings – of which only 13 have diameters greater than 50 kilometers – as well as dense rings that contain millions of embedded moon-lets and innumerable smaller ring particles.

Some important moons of Saturn are Titan, and Enceladus. Enceladus is a moon of Saturn with a surface of ice and an ocean inside. Enceladus is one of the smallest of Saturn's moons that is spherical in shape—only Mimas is smaller—yet is the only small Saturnian moon that is currently endogenously active, and the smallest known body in the Solar System that is geologically active today. Its surface is morphologically diverse; it includes ancient heavily cratered terrain as well as younger smooth areas with few impact craters. Many plains on Enceladus are fractured and intersected by systems of lineaments.

Titan is the largest moon of Saturn and the second-largest natural satellite in the Solar System. It is the only moon known to have a dense atmosphere, and the only known body in space, other than Earth, where clear evidence of stable bodies of surface liquid has been found. Titan is one of seven gravitationally rounded moons in orbit around Saturn, and the second most distant from Saturn of those seven. Frequently described as a planet-like moon, Titan is 50% larger (in diameter) than Earth's Moon and 80% more massive. It is the second-largest moon in the Solar System after Jupiter's moon Ganymede, and is larger than the planet Mercury, but only 40% as massive. Titan's atmosphere is largely nitrogen, with large amounts of methane and ethane clouds.

There are still 29 moons yet to be named (as of October 2019), using names from Gallic, Norse and Inuit mythology based on the orbital groups of the moons. Twenty of these moons are in line to receive permanent designations, with seventeen Norse, two Inuit, and one Gallic name expected.

References

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