Saturn and Her Moons

Saturn

Introduction

The intention of this paper is to give the history, explain the atmospheric conditions, describe the characteristics and explain the path of movement of Saturn. I will also describe the personality of Saturn.

History

Saturn was named after the Roman god of agriculture. When most think about Saturn they mention the rings system. Saturn is visible with the naked eye and because of this Saturn has been known since prehistoric times. It was not until the creation of the telescope that the rings of Saturn were observed (Greene, 2011).

In 1610, Galileo Galilei, an Italian scientist, was the first to study Saturn with the use of a telescope. Galileo first believed the rings of Saturn were actually two moons. However, two years later these "moons" were no longer there, and two years after this they reappeared. Galileo then decided that the rings were some sort of arms (Kerr, 2002). In 1659 Christiaan Huygens, a Dutch astronomer, was able to determine that the "arms" of Saturn were not arms at all, but a ring system. Huygens discovered Titan, which is one of Saturn's moons, and Saturn's largest (Kerr, 2002). Jean-Dominique Cassini, an Italian-French astronomer, around the year of 1962, discovered four more moons of Saturn. They are known as Iapetus, Rhea, Tethys, and Dione. Cassini in 1975 also discovered the Cassini Division, which is a "narrowing gap that splits Saturn's ring system into two parts" (Kerr, 2002). J.E. Keeler discovered in the 19th century that Saturn's ring system is not a consistent mass but in fact comprised of small particles (Kerr, 2002).

The Atmosphere

Saturn's atmosphere consists of many features that are comparable to Jupiter, such as the red, brown, and white spots. Also there are features such as vortices, bands, and eddies. The atmosphere on Saturn is not as active as that of Jupiter's. There was an exception to this between September and November of 1990. At this time a large storm system that was light in color appeared close to the equator. This storm system expanded to a size of 20,000km, then the storm system spread around the equator before disappearing. This storm system was named "Great White Spot". Storms that have had similar likeness to the Great White Spot have been observed since the late 19th century at about 30 year intervals. Since these storm systems are close to the orbital period of Saturn it is thought that these storms are a seasonal phenomena (Hubbard, 1994-2009).

The atmosphere of Saturn is mostly made up of hydrogen and helium. There are traces of methane, ammonia, hydrogen sulfide, and ethane. Hydrogen makes up about 96 percent of the atmosphere and helium makes up about 3 percent, while the remaining elements make up the rest of the atmosphere (Dunn, 1998-2000).

The atmospheric temperatures on Saturn are at a constant of approximately 140 to 150 kelvins (K), which are at pressures below 1 millibar. At the stratosphere temperatures steadily decrease with rising pressure and broaden downwards from 1 to 60 millibars. At the stratosphere level the coldest temperature of 82K is reached. The temperature increases at higher pressures or deeper levels. This area is equivalent to the troposphere layer of Earth, which is Earth's lowest layer (Dunn, 1998-2000).

Characteristics of Saturn

The shape of Saturn is clearly flattened at the poles, but bulging at the equator. Saturn's polar diameters and equatorial diameter vary about 10 percent. Saturn's interior is made up of layers. First is the rocky core at the center. Then just above the center is a liquid metallic hydrogen layer, followed by the next layer above this called a molecular hydrogen layer. Within these layers are traces of ices present. Saturn has an interior that is very hot which reaches to 12000K at the core. The amount of energy that Saturn receives from the sun is less than what Saturn radiates into space. (Dunn, 1998-2000)

Some characteristic facts about Saturn; Saturn is the sixth planet from the sun with an average distance of 1.425 x 109km. the diameter of Saturn is 120,000km with a mean radius of 58232 km. the mass of Saturn is 95.2 , with a density of 0.69( /g/m^3), and a gravity of 1.16. the orbit period of Saturn, given in earth years, , is 29.46, and the rotation period, given in earth days, is o.436 (Greene, 2011). Below is a table that gives some of the physical properties of the giant planets.

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Movement of Saturn

Saturn is known to have a regular orbit, which is that it rotates around in the sun in the same direction as the sun rotates. Saturn has a rotational axis that is tilted to its orbital plane by about 26.7 degrees, which is unlike that of Jupiter. This tilt allows Saturn to have season. Each season however lasts more than seven years, compared to Earth's season. As a result of this tilt Saturn's rings are visible to the observers on Earth. The rings are on a 30 year cycle. You can view from Earth the ring's sunlit northern side for 15 years. There is a short interval when you are not able to see the rings because the Earth crosses the ring plane (Hubbard, 1994-2009).

As mentioned under the characteristics of Saturn it takes Saturn about 29 ½ earth years to complete one orbit around the sun. Saturn is approximately 400,000,000km from the sun. There is no single rotation period on Saturn; because of this these rotation periods have been assigned to different regions. There are three regions, System I which has a period that lasts 10hr 14m and surrounds the equatorial zone. The other two regions, System II, and System III have a rotation period of 10 hr 39m 24 sec, which all other latitudes of Saturn have been assigned to (Hubbard, 1994-2009).

Personality of Saturn

Saturn has many interesting features. One of Saturn's features is the rings. When you look through a small telescope the rings of Saturn may appear to look like one solid ring. However, Saturn is known to have thousands of rings, each nested inside another. In 1850 James Clerk Maxwell showed us that these rings are not solid, but are actually made up of billions of particles, the smallest particles being grains of dust. There are also house sixed boulders that are the largest particles. All these particles together are orbiting the planet. (Hubbard,