The Saturn is the sixth planet of our solar system and second largest planet in size after Jupiter. It is unique planet in solar system due to planetary rings. This gas giant can be seen by unaided eye as unblinking star. Saturn name was given on the name of agricultural Roman god. The Saturn was formed with creation of solar system about 4.5 billion years ago.
The diameter of Saturn is 116460 km which is 9 times bigger than the earth. This planet is 1.434 billion km away from the sun and closet distance from the earth is 1.2 billion km.
The interior of Saturn is made of core of Iron- Nickel and rock having 25000km. This core is covered by metallic hydrogen than layer of liquid hydrogen and liquid helium and outer most is gaseous layer which is about 1000km. Magnetic field is present on Saturn due to electric current in liquid hydrogen layer but intensity of magnetic field is weaker than the earth. But due to bigger size its magnetic moment is 580 times greater than earth. This planet is famous for planetary rings which are made of ice particles, rocky particles and dust.
Surface of Saturn :
This gas giant is made of hydrogen and helium so it has no any dense surface even it has solid core. Due to rotation of Saturn its shape is oblate spheroid like Flattened on poles and bulges on equator. Average specific gravity of planet is 0.69 gm/ cubic cm which is less than water. Saturn is very hot in center. Temperature at the core is about 11700 degree Celsius and it produces about 2.5 times more energy into space which it receives from the sun.
Orbit and Rotation :
One day on the Saturn is 10.7 hours. Average rotation speed of Saturn is 9.68 km/s and takes 10.758 earth’s days ( 29.4 yrs) to complete in one revolution around the sun. Just like the earth, Saturn is also tilted by 26.73 degree which shows that there may be possibilities of seasons. The Saturn’s elliptical orbit is inclined by 2.48 degree relative to the earth.
The Saturn outer layer is made of Hydrogen and Helium. Outer layer is composed of 96.3 % hydrogen and 3.25% helium. Methane (0.45%), acetylene, ethane, peopane, phosphine are also detected in atmosphere of the Saturn. The upper cloud of atmosphere is made of ammonia crystals and lower cloud is made of ammonium hydrosulfide. Due to ultraviolet radiations from the sun in upper layer methane photolysis chemical reaction is done. The temperature and pressure is varies in clouds layers. In outer layer temperature is 100K-160 K and pressure is 0.5-2 bar with ammonia ice. When the pressure goes to 3.5 to 9 bar, the water ice clouds starts and temperature is 185K-270K. In inner layer pressure is 10-20 bar and temperature is 270K-330K where water droplets are present. The wind speed on the Saturn is 500m/s which is second fastest than Neptune in solar system.
On the north polar vortex at 78 degree, hexagonal wave pattern was found which each side is 13800 km long. This entire pattern rotates about speed of the spinning rate of Saturn planet. On November 2006, NASA reported hurricane type storm on southern pole which was seen like eyewall. Wind speed on southern pole can be 550 m/s.
Rings of Saturn :
Rings of the Saturn are most beautiful and extensive ring system of any planet in solar system. These rings are made of generally water ice and rocky materials which are in the size of microns to meters or kilo meters. In 1610, first time these rings were discovered by Galileo but it could not be able to see it. In 1655, Christiaan Huygens was the first person who described the rings as a disc around the planet.
By regular telescope three rings are visible around the Saturn and by powerful telescope 8 rings can be seen. But about 30 rings were seen when spacecraft Cassini orbited the Saturn. The rings of Saturn are start at 6630 km from equator to 120700 km outward with thickness approximately 20m. They are made of water ice with Tholin (Organic compounds formed by solar ultraviolet with carbon compound) impurities and about 7% of amorphous carbon. The rings of Saturn are relatively close to each other having gaps between the rings which is 4700 km wide is called Cassini division which separate Ring A and Ring B. Other rings D,E,F and G also recently discovered. Sometimes large storms are present on Saturn which can be visible from earth.
Moon of Saturn :
The Saturn has largest number of moons in solar system which are 82. Among 82 moons, 24 moons are regular satellite which have prograde orbit not much inclined to saturn’s equatorial plane. Remaining 58 moons are irregular satellite which orbit much far from Saturn with high inclination. Following are the major moons of Saturn.
Titan is the biggest moon of Saturn and second largest moon in solar system after Jupiter’s Ganymede and bigger than Mercury. This was discovered by Christiaan Huygens in 1655. Titan is the sixth planet which is 50 % bigger than earth’s moon and 80% massive. Titan is made of rocky material and ice. Its rocky core is covered by ice and its sub surface is composed of ammonia rich liquid water. Liquid hydrocarbon lakes were discovered on Polar Regions of titan by Cassini-Huygens mission in 2004. Surface of the moon is smooth, some crater and some places cryovolcanoes are found.
Atmosphere of titan is generally composed of Nitrogen and some part of Methane and Ethane clouds. Rainy and windy climate of Saturn create its surface features like earth such as dunes, lakes, rivers, sea etc. Due to these liquid and nitrogen atmosphere, its methane cycle is similar to earth’s water cycle. Its surface temperature is 94K.Titan orbits the Saturn in 15 days and 22 hours and it is tidally locked.
The Hyperion is the unique moon in solar system by its irregular shape. It was discovered by William Cranch bond, George Phillips Bond and William Lasseli in 1848. It is the first non-round shape moon having chaotic rotation and sponge like appearance.
It is mainly composed of mainly water ice and small amount of rock. Its surface has deep and sharp edge craters so its appearance is looks sponge type. In bottom of craters, black material is filled up. Its chaotic rotation is so wobbles that its orientation is unpredictable.
The Enceladus is the sixth largest moon of the Saturn which was discovered by William Herschel on August 28, 1789. Its diameter is about 500 km. Its surface is covered with fresh and clean ice which makes the moon most reflective body in the universe. At noon its surface temperature would be -198 degree Celsius (-324F). Cassini spacecraft discovered water rich plumes venting from southern pole. Cryovolcanoes shoots geyser like jet of water vapour, molecular hydrogen, sodium chloride crystals and ice particles into shapes which escape materials create the Saturn’s E-ring. About more than 100 geysers are found on Saturn’s surface. It takes 32.9 hours to orbit the Saturn.
Tethys was formed from saturnian sub nebula after formation of Saturn. This moon was discovered on 21 March 1684 by G.D. Cassini. Its diameter is about 1060 km and density is 0.98 gm/cubic cm. It is second brightest moon of the Saturn. It is mainly made of water ice and small amount of rock. Its surface is covered with water ice and some unidentified black materials. Number of craters and faults/graben are present on its surface. Tethys is the 16th largest moon in our solar system and its mass is 1% less than the earth moon.
The Dione is the 15th largest moon in our solar system. It was discovered by G D Cassini on 21 March, 1684. This moon is about 1122 km in diameter is named after Titaness Dione Greek methodology. It orbits the Saturn in 2.73 days. This moon is too massive composed about two third of water ice and remaining is silicate dense core. Liquid salt water was also discovered on its surface.
This planet was discovered on December 23, 1672 by G D Cassini. It is the ninth largest moon in solar system and second largest moon of Saturn planet. It is named Rhea after the titan Rhea Greek methodology. It is composed of 75% water ice and 25% rock and gravity of the moon is 1.236 gm/ cubic cm. Its surface is covered with heavy craters. This moon has tenuous atmosphere which consists of oxygen and carbon dioxide. Its surface temperature at noon is about -174 degree Celsius (99 K ).
Iapetus is the third largest moon of Saturn and 11th largest moon in our solar system. It was discovered by G D Cassini on 25 October, 1671. This moon is tidally locked, so its one face is always towards the Saturn. The diameter of the moon is 1492 km . Its orbit is very unusual due to its high inclination. This moon is composed mainly water ice and some rocky material. There is equatorial ridge on its surface which makes the moon unique. This ridge is 20km in height which is tallest in entire solar system. Due to equilateral ridge the shape of the moon is like walnut.
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Authored by BK Suthar.
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