Saturn / Introduction

Saturn is the Lord of the Rings. It belongs to the group of the gas giants and is the sixth planet from the sun.

The ring system is the most characteristic feature of the planet. It was first observed by Galileo in 1610. As he had only a modest telescope by todayís standard, he mistook the feature as being a group of moons. In 1656, the Dutch astronomer Huygens discovered that they were actually rings.

The distance between the sun and Saturn is nearly double the distance between the sun and Jupiter. Very powerful telescopes are necessary to observe the rings of the planet from the earth. They consist mainly of blocks of ice and rocks.There is a distinct separation between the rings called Cassiniís division after its discoverer Cassini. In his honor, the spacecraft sent out in October 1997 to explore Saturn was called Cassini.
The spacecraft will also examine Saturnís largest moon, Titan. It appears that Titan has an atmosphere, which is believed to be very similar to the very initial atmosphere that once covered the earth. Scientists therefore hope that the results from Titan will throw some light on the development of life on our own planet.Saturn has 22 confirmed moons but astronomers are convinced that there are several more to be dicovered over the next few years.

The Cassini spacecraft will reach Titan in 2004. Saturn orbits the sun once every 29.5 years with a mean distance tothe sun of 1.5 billion kilometers.

Its rotational velocity is nearly as great as that of Jupiter. One dayon Saturn equals approximately 10 hours and 25 minutes. Similar to Jupiter, Saturn is therefore slightly flattened at the poles. The equatorial diameter is 120,500 kilometers while the distance from pole to pole is only 108,800 kilometers.

Its layer of ionized hydrogen is considerably thinner than that of Jupiter and therefore, the rotational velocity creates only a weak magnetic field.Similar again to Jupiter, there are bright and dark cloud bands to be observed around Saturn. Saturn appears to be a much more stormy planet than its distant neighbor with winds that howl at speeds in excess of 2000 kilometers per hour around the areas near the equator. The temperature within these storms can be as low as minus 180 įC.

Like Jupiter, Saturn emits more energy than it receives from the sun. The mass of Saturn is 95 times larger than that of the earth while its density is below the density of water. In other words, Saturn would be the only planet in the Solar System that would float on water.

Orbit of Saturn

Saturn completes one orbit around the sun every 29 years and 167 days. Its distance from the sun is between 1.35 and 1.5 billion kilometers. The planet completes a rotation on its own axis every 10 hours and 25 minutes, which is a slightly longer period than that of Jupiter.

Similar to the earth, the planetís axis of rotation is inclined and the inclination of the equator relative to the orbit plane is 27 degrees. The rings of Saturn are therefore equally inclined to its orbit and they appear to the observer on the earth in a different position.

At two positions during a Saturn year, the rings are barely visible from the earth as we are then looking right at the rim of the rings. In 2002 we will have the opportunity to see the rings at the best possible angle from the earth.

Saturn Surface

Saturn consists of a core of rock and ice with a diameter of approximately 30,000 kilometers. The core is surrounded by a mantle of ionized hydrogen. This layer is thinner than that of Jupiter. This fact and the slower rotational speed of the planet result in a magnetic field that is twenty times weaker than that of its neighbor.

The planet has a very largelayer of liquid hydrogen beneath its surface.

In the zone of the equator, there are prominent bands of cloud. Astronomers have observed storms and turbulence in these clouds, similar to the Great Red Spot on Jupiter.

However, the storms on Saturnare not as powerful and persistent as those on Jupiter.The most turbulent zones are located around the equator where wind velocities of up to 2000 kilometers per hour were observed.

The atmosphere of Saturn consists mainly of hydrogen and helium. These light elements result in a density of only 0.69 g/cm3, which is less than the density of water. Saturn is actually the only planet in our Solar System with a density less than that of water.

Saturn Rings

Saturn is not the only planet with rings as all the other large planets (Jupiter, Uranus, Neptune) also feature ring systems. However, none of these are as impressive and complex as those of Saturn.

The rings were discovered by Galileo in 1610, who had obviously no access to the powerful telescopes available today. He came to the conclusion that the objects he saw were moons. Only about 50 years later, the astronomer Huygens discovered the ring nature of these objects.

From the earth we can see three rings. Of these, ring A is the most distant from the planet. Inside its circle, there is a small gap where the inner moons of Saturn orbit.

Ring B features dark radial patterns. They lead scientists to believe that matter in ring B is not dispersed equally, most probably as a result of the electromagnetic fields in the dust clouds.

Ring C is the faintest of the three rings visible from the earth and consists, like A and B, of several single ringlets.Four additional rings (D to G) were only recently discovered by spacecraft. Ring E consists of the finest dust particles and is the largest of the rings. Parts of ring F appear to be intertwined as a result of the forces of the gravitational fields of the shepherd moons Pandora and Prometheus.

Ring G and D, which extend to the edge of the atmosphere of the planet are barely visible. Although the rings are of enormous dimensions, they contain very little matter and their total mass amounts to approximately 1/25,000 of the mass of Saturn.

The particles in the rings are rocks and ice. It is believed that one of the first moons of Saturn entered the planets gravitational field and was crushed by the resulting forces.

The clear separation between the A ring and the B ring was discovered in 1675 by the astronomer Cassini. This gap is called Cassiniís division and extends over a distance of approximately 4000 kilometers. Photographs taken by the Voyager spacecraft reveal that the area of Cassiniís division is not completely empty as it contains several dozens of very small ringlets consisting of dust particles ranging in size from 10 meters to a few nanometers.

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