Saturn (0)

Tallinna Tööstushariduskeskus
Saturn
Referaat
Tallinn 2014

Sissejuhatus

Saturn is one of the most interesting planets in the solar system. It is the sixth planet in the solar system, and is most famous for its stunning array of rings . It is a very easy planet to pick out in the sky because it is one of the brightest lights in the shy. It also has a very faint greenish color that makes it stand out from the rest of the objects in the sky ("Astronomy for Kids "). Saturn is the second largest planet in the solar system, Jupiter being the only planet that is bigger. It also has at least eighteen moons , more than any other planet in the solar system. There have been three voyages to this extraordinary planet, and one is still in process today . The Pioneer II traveled to Saturn in September of 1979, the Voyager missions took place in the 1980's and the Cassini probe began it's voyage in October of 1997 (Kuhn 280-282). There are many aspects of Saturn that make it one of the most extraordinary planets in this solar system. Galileo Galilei was the first to view Saturn's system of rings in the year 1610. Because he happened to be viewing their edge , he failed to recognize them as rings. In fact, he mistakenly interpreted the rings to be two moons similar to those he had discovered near the planet Jupiter. In 1655, a Dutch astronomer named Christiaan Huygens was able to discern what Galileo had thought to be moons as rings. Huygens benefited from a much improved telescope than that used by Galileo. A second moon of Saturn called Iapetus was found by the Italian astronomer Cassini in 1671. He also discovered, in 1675 , that Saturn had more than one ring, i.e. a concentric pair of rings. A third ring was discovered by Johann Franz Encke in 1837 using a telescope at the Berlin observatory. Until Pioneer II approached Saturn in September of 1979, the planet was thought to have but three rings (Yenne 125). Saturn is the sixth planet in the solar system, located between Jupiter and Uranus. Its average distance from the Sun is over 850 million miles , compared to Earth's which is 93 million miles. Saturn's orbit , the path it follows around the Sun, is nearly a circle. The closest the planet has come to the Sun is around 840 million miles, while the furthest away it gets is 930 million miles. Since Saturn is so far away from the Sun, it takes a very long time for it to complete its orbit of the Sun. Saturn's year equals 29 and one- half Earth years . A day on Saturn, though, is much shorter than an Earth day ;it rotates around once every ten and one-half hours (Kuhn 280-282). Saturn is the second largest planet in the solar system. Jupiter is the only planet that is larger. The gas giant is 72 thousand miles in diameter, almost ten times the size of Earth. In spite of its huge size, though, Saturn weighs very little . It is a very light gas planet. Saturn is the least dense planet in the solar system-- so light, in fact, that it would float in water. This planet is mostly composed of hydrogen and helium, like Jupiter, but it is much less dense. The combination of its light weight and fast rotation causes Saturn to spread out, or oblate, its center . Since Saturn is a gas planet, it does not have a solid surface. Spacecraft are unable to land on this type of surface. The clouds that are seen when looking at Saturn are just the top layer of a very deep layer that covers a center of liquid hydrogen. The clouds are blown by constant winds that reach speeds up to one thousand miles per hour at the equator of the planet ("Great Space Place"). The rings of Saturn are more spectacular than those of any other planet. Although this planet's rings are very wide, extending from the top of its atmosphere to well beyond the orbits of its closest moons, they are very thin , measuring no more than a few kilometers (about a mile) in thickness ("Great Space Place"). The Pioneer 11 flyby made several discoveries about the rings. The rings are made of particles that are dust - sized up to large mountain-sized masses, with the average size being in the marble to basketball range - about 10 centimeters (four inches). These particles are extremely cold and are possibly composed of frozen water and other ices. An extensive cloud of hydrogen was also discovered around the rings. The rings might have resulted when a moon or a passing body ventured too close to Saturn. The unlucky object would have been torn apart by great tidal forces on ts surface and in its interior . In , the object may not have been fully formed to begin with anddisintegrated under the influence of Saturn's gravity. A third possibility is thatthe object was shattered by collisions with larger objects orbiting the planet ("Pioneer 10, 11"). Voyager I provided much more detail on the beauty , complexity, and sometimes baffling nature of the rings. The six known rings are actually composed of hundreds of tiny , thin ringlets with intervening spaces, so that the whole ring system looks something like the grooves in a phonograph record . Even the Cassini division, once thought to be empty space between the A and B rings, contains several dozen ringlets. There are far too many rings to be explained by the present theories of how planetary rings form and remain stable. The thin outer F-ring, discovered by Pioneer 11, was resolved into three distinct but intertwined ringlets. This braided ring structure is very difficult to explain ;it seems likely that both electrical and gravitational forces are at work . This voyage also helped to discovered that two of Saturn's small moons, one on each side of the F-ring, may act as "shepherds," their gravitational attraction keeping the ring particles on track between the orbits of the moon (Yenne 126). The first spacecraft flyby accomplished by Pioneer 11 in 1979 accomplished many findings of Saturn's composition . The planet has an internal heat source like Jupiter and radiates about twice as much energy as it receives from the Sun. As suspected, Saturn must have internal shells of liquid and metallic hydrogen, small amounts of helium, ammonia, water, and perhaps a small rocky core. A magnetic field was also discovered around Saturn, larger than the Earth's, but smaller than that of Jupiter. It is five times as weak as predicted by theory. The axis of this magnetic field is aligned parallel to the planet's rotation axis, contrary to thecircumstances in both Jupiter and Earth. The boundary of the magnetic field varies due to changes in the pressure of the solar wind on the sunward side,as was found in the case of Jupiter. The atmosphere of Saturn has weak bonds and there is a high haze , perhaps composed of crystals of ammonia ice, above the clouds. Apparent high-speed jet streams were also detected in the atmosphere. Confirming ground - based measurements, the cloud-top temperatures were measured at about -200 degrees Celsius (-330 degrees Fahrenheit), and only about 73 degrees Celsius (130 degrees Fahrenheit) above absolute zero . The Pioneer 11 voyage also discovered radiation belts that are weaker than those of Jupiter. The radiation is absorbed by the rings and moons of Saturn. Cutoffs in the radiation data were used to infer the presence of additional rings and moons beyond those already known from visual observations ("Pioneer 10, 11"). Saturn has more moons than any other planet in the solar system. Nine (possibly ten) of these moons have been detected from Earth. Voyager 1's encounter to Saturn provided several new discoveries about Saturn's moons. Six, tiny unnamed moons were photographed on this mission , some of them for the first time. Satellites 10 and 11 share the same orbit and must frequently undergo some orbital "evasive actions " to avoid colliding. Satellite