Named after
the Roman god of agriculture,
Saturn
at a distance of 1,429,400,000 kilometers
or 9.55 AU is the sixth planet from the
Sun
and with a diameter of 119,300 kilometers is after Jupiterthe 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 plus
small amounts of helium and methane. Winds near the equator often reach
speeds in excess of 1,700 km an hour. The mean
temperature at cloud level is -125 °C, steadily
warming as
we go deeper,
the gas eventually resembling a hot liquid, then under increasing
pressure molten metal. Eventually we reach an extremely hot
coating consisting of water, methane and ammonia in a liquid mix
wrapped around a rocky core.
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.” [1]
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 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 (early estimates place its diameter at 22.5 million kilometers) almost invisible new
ring 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. 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]
“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.
