Saturn


Named after the Roman god of time, plenty, the harvest and agriculture, Saturn, with an orbital average of 9.58 AU, is the sixth planet from the Sun and with a diameter of 120,536 kilometers the second largest planet in the Solar System.  

Saturn rotates very quickly resulting in visibly flattened poles and a day only 10 hours and 39 minutes long. A true gas giant, its atmosphere is mainly hydrogen with small amounts of helium and methane its winds near the equator often clocking speeds in excess of 1,700 km an hour. The mean temperature at cloud level is -125 C. Its internal structure probably consists of an iron-nickel and rock core, surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and helium, and above the Frenkel line [1] a gaseous outer layer.

Saturn is often referred to as the “Ringed Planet” the exact origin of the rings unknown. One theory is that they are the remnants of moons fragmented by comet or meteor impact, their composition everything from dust to rocks to chunks of ice the size of icebergs. Nearby satellites define the elaborate structure of the rings with their gravity fields, a phenomenon known as “shepherding.” [2]

Regardless of how they were formed and whatever their composition they make Saturn one of the most spectacular planets in our planetary family. The nine main rings from Saturn outward are, D,C,B, A,F,G and E along with two new rings R/2004 S1 and R/2004 S2 located between A and F and discovered by the Cassini spacecraft [3] in 2004. The E ring was until recently considered the outermost, its orbit extending some 483,000 km from the planet's center. We say until recently, because on October 6, 2009, three astronomers, Anne J. Verbiscer, Michael F. Skrutskie and Douglas P. Hamilton announced the discovery of a gigantic almost invisible new ring (early estimates place its diameter at 22.5 million kilometers or 14 million miles) found using NASA's Spitzer Space Telescope. The disk envelopes the orbit of the moon Phoebe, thought to be the source of its dust, and as opposed to the wafer-thin inner rings is 20 times Saturn's diameter thick, orbits in a retrograde direction and is tilted at a 27 degree angle.

On July 19, 2013, during a pre-arranged interplanetary photo op, in which NASA urged Earthlings to "wave at Saturn," Cassini looked back toward the Earth-Moon system from Saturn's shadow and snapped a picture. (Spacecraft rarely turn to face Earth from the outer solar system in order to avoid the damaging effects of direct sunlight.)

To date Saturn has 62 known moons: Pan, Daphnis, Atlas, Prometheus, Pandora, Epimetheus, Janus, Mimas, Methone, Pallene, Enceladus, Tethys, Telesto, Calypso, Dione, Helene, Polydeuces, Rhea, Titan, Hyperion, Iapetus, Kiviuq, Ijiraq, Phoebe, Paaliaq, Skathi, Albiorix, Erriapus, Siarnaq, Tarvos, Mundilfari, Narvi, Suttungr, Thrymr, Ymir, Aegir, Bebhionn, Bergelmir, Bestla, Farbauti, Fenrir, Fornjot, Hati, Hyrrokkin, Kari, Loge, Skoll, Surtur, Greip, Jarnsaxa, Tarqeq, Anthe, Aegaeon and nine as yet unamed S/2004 S 7, S/2004 S 13, S/2006 S 1, S/2004 S 17, S/2004 S 12, S/2006 S 3, S/2007 S 2, S/2007 S 3 and S/2009 S 1.


[1] The Frenkel line refers to a change in the dynamics and structure of fluids. Below the line fluids are "rigid" and "solid-like" while above they are "soft" and "gas-like."

[2] “Shepherd” moons are small satellites orbiting within gaps or at the periphery of planetary rings their gravitational presence producing a distinct edge to the matter comprising the ring.


[3] Cassini-Huygens, a flagship-class NASA-ESA-ASI robotic spacecraft, arrived in the Saturn system in 2004 after flybys of Earth, Venus and Jupiter, its mission to study Saturn its attendant satellites and rings.




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