Saturn: The Planet

Saturn lies between Uranus and Jupiter and along with Neptune, these four planets are referred as the Jovian, meaning 'Jupiter-like', planets. Saturn is named after the Roman God Saturnus, equated to the ancient Greek God Kronos and Hindu God Shani. Its symbol represents the God's sickle. The average distance between Saturn and the Sun is over 1.4 billion km and it has an equatorial diameter of 119,300 kilometers (74,130 miles). Its average orbital speed is 9.69 km/s and takes about 10,759 earth days to complete one revolution around the Sun.

Physical Characteristics
The planet Saturn appears in beautiful pale yellow color with hints of orange. It is mainly composed of hydrogen, with small proportions of helium and trace amounts of other chemicals. Like any other planet, Saturn also has separate layers, the top cloud layer is made up of ammonia crystals, and below it are clouds of ammonium hydro sulfide or water. Underneath this layer, pressure increases to the point that hydrogen gets compressed into liquid hydrogen and even deeper down, it becomes metallic hydrogen. Its interior consists of a small core of rock and ice, surrounded by a thick layer of metallic hydrogen and a gaseous outer layer. Due to its lower density, rapid rotation, and fluid state, Saturn is an oblate spheroid, flattened at the poles and bulged out at the equator. Saturn is about 95 times the mass of the Earth and only ⅓ the mass of the Jupiter. The temperature on Saturn ranges from -150 °C at the high cloud tops to 11,700 °C at the internal core.

Discovery of Saturn
The ancient people have known about Saturn for thousands of years, as it is visible through the unaided eye and appears as one of the brightest star in the sky. Hence, it is almost impossible to point out who actually discovered planet Saturn. Galileo Galilei was the first who observed Saturn through a telescope in 1610. He was unable to distinguish its rings and thought that the planet might have ears or two large moons on either side. Christiaan Huygens who was a Dutch astronomer, observed Saturn in 1659, and stated that the 'arms' around Saturn were a system of rings. He was the first to observe Saturn’s moon Titan. On September 1, 1979, NASA’s Pioneer 11 spacecraft made a flyby of the planet, at a distance of 21,000 km above the planet’s cloud tops and sent back the first close-up images of Saturn.

Rings of Saturn
The beautiful translucent rings of Saturn are made up of water ice, and might be as old as Saturn itself. Their size ranges from microscopic to boulders larger than a house. They start 6,630 km above Saturn’s equator and extend out to a distance of 120,700 km, having an average thickness of only 20 meters. Cassini Division and Encke Gap are the two large gaps in the rings. The Cassini division is 4,800 km wide and was discovered by Giovanni Domenico Cassini in 1675. The various rings around Saturn have been designated with letters that goes up to the alphabet G. The three main sections that can be seen from the Earth through a telescope, are the A, B, and C rings.

Moons of Saturn
Saturn’s largest moon is Titan, discovered by Christiaan Huygens in 1655 and measures 5151 km across. It is the second largest moon in the solar system after Jupiter's moon Ganymede. Saturn's other moons like Tethys, Dione, Rhea and Iapetus were discovered by Giovanni Cassini in the same century. Saturn's closet moon is Mimas which orbits about 185,000 km above the center of Saturn and measures 397 km across. Enceladus is the next largest moon of Saturn and measures 504 km across, and orbits at 238,000 km from the center of Saturn. Recently, NASA’s Cassini spacecraft discovered geysers of water ice pouring out of Enceladus’ southern pole and it is believed that there could be vast reserves of liquid water underneath the moon’s icy surface. Until now, 60 of the Saturn's moons have been discovered out of which 52 have been given names.

According to astronomers, life can't exist on Saturn as it is mainly comprised of hydrogen and helium. But Saturn's moons consist of significant amounts of water ice, and their gravitational interaction with Saturn probably keeps their interiors warm. Still, there are many intriguing locations and facts to explore about this planet that will keep astronomers busy for years to come.