Saturn Information Saturn is the sixth planet from the Sun. It is a gas giant, the second-largest planet in the solar system after Jupiter. Saturn has a prominent system of rings, consisting of mostly ice particles with a smaller amount of rocky debris. It was named after the Roman god Saturn. Its symbol is a stylized representation of the god's sickle.
The Chinese, Korean, Japanese, and Vietnamese cultures refer to the planet as the earth star, based on the Five Elements. Physical Characteristics  Saturn's shape is visibly flattened at the poles and bulging at the equator (an oblate spheroid); its equatorial and polar diameters vary by almost 10% (120,536 km vs. 108,728 km). This is the result of its rapid rotation and fluid state. The other gas planets are also oblate, but to a lesser degree. Saturn is also the only one of the Solar System's planets less dense than water, with an average specific density of 0.69. This is only an average value, however; Saturn's upper atmosphere is less dense and its core is considerably more dense than water.
Saturn's interior is similar to Jupiter's, having a rocky core at the center, a liquid metallic hydrogen layer above that, and a molecular hydrogen layer above that. Traces of various ices are also present. Saturn has a very hot interior, reaching 12000 K at the core, and it radiates more energy into space than it receives from the Sun. Most of the extra energy is generated by the Kelvin-Helmholtz mechanism (slow gravitational compression), but this alone may not be sufficient to explain Saturn's heat production. An additional proposed mechanism by which Saturn may generate some of its heat is the "raining out" of droplets of helium deep in Saturn's interior, the droplets of helium releasing heat by friction as they fall down through the lighter hydrogen.
Saturn's atmosphere exhibits a banded pattern similar to Jupiter's (in fact, the nomenclature is the same), but Saturn's bands are much fainter and they're also much wider near the equator. Saturn's winds are among the Solar System's fastest; Voyager data indicates peak easterly winds of 500 m/s (1116 MPH). Saturn's finer cloud patterns were not observed until the Voyager flybys. Since then, however, Earth-based telescopy has improved to the point where regular observations can be made.
Saturn's usually-bland atmosphere occasionally exhibits long-lived ovals and other features common on Jupiter; in 1990 the Hubble Space Telescope observed an enormous white cloud near Saturn's equator which was not present during the Voyager encounters and in 1994 another, smaller storm was observed. The 1990 storm was an example of a Great White Spot, a unique but short-lived Saturnian phenomenon with a roughly 30-year periodicity. Previous Great White Spots were observed in 1876, 1903, 1933, and 1960, with the 1933 storm being the most famous. The careful study of these episodes reveal interesting patterns; if it holds another storm will occur in ~2020.
Astronomers using infrared imaging have shown that Saturn has a warm polar vortex, and is the only planet in the solar system known to do so.
Rotational Behavior Since Saturn does not rotate on its axis at a uniform rate, two rotation periods have been assigned to it, like in Jupiter's case: System I has a period of 10 h 14 min 00 s (844.3�/d) and encompasses the Equatorial Zone, which extends from the northern edge of the South Equatorial Belt to the southern edge of the North Equatorial Belt. All other Saturnian latitudes have been assigned a rotation period of 10 h 39 min 24 s (810.76�/d), which is System II. System III, based on radio emissions from the planet, has a period of 10 h 39 min 22.4 s (810.8�/d); because it is very close in value to System II, it has largely superseded it.
While approaching Saturn in 2004, the Cassini spacecraft found that the radio rotation period of Saturn had increased slightly, to approximately 10 h 45 m 45 s (� 36 s). The cause of the change is unknown. Planetary Rings Saturn is probably best known for its planetary rings, which make it one of the most visually remarkable objects in the solar system. This is a list of the 15 named rings of Saturn, and the gaps between them. | Name | Distance from Saturn's center (km) | Width (km) | Named after | | D Ring | 67,000 - 74,500 | 7,500 | | | C Ring | 74,500 - 92,000 | 17,500 | | | Columbo Gap | 77,800 | 100 | Charles-Augustin de Coulomb ??? | | Maxwell Gap | 87,500 | 270 | James Clerk Maxwell | | B Ring | 92,000 - 117,500 | 25,500 | | | Cassini Division | 117,500 - 122,200 | 4,700 | Giovanni Cassini | | Huygens Gap | 117,680 | 285-440 | Christiaan Huygens | | A Ring | 122,200 - 136,800 | 14,600 | | | Encke Division | 133,570 | 325 | Johann Encke | | Keeler Gap | 136,530 | 35 | James Keeler | | R/2004 S 1 | 137,630 | ? | | | R/2004 S 2 | 138,900 | ? | | | F Ring | 140,210 | 30-500 | | | G Ring | 165,800 - 173,800 | 8,000 | | | E Ring | 180,000 - 480,000 | 300,000 | |
Physical Characteristics  The rings can be viewed using a quite modest modern telescope or with a good pair of binoculars. They extend from 6,630 km to 120,700 km above Saturn's equator, and are composed of silica rock, iron oxide, and ice particles ranging in size from specks of dust to the size of a small automobile. There are two main theories regarding the origin of Saturn's rings. One theory, originally proposed by �douard Roche in the 19th century, is that the rings were once a moon of Saturn whose orbit decayed until it came close enough to be ripped apart by tidal forces. A variation of this theory is that the moon disintegrated after being struck by a large comet or asteroid. The second theory is that the rings were never part of a moon, but are instead left over from the original nebular material that Saturn formed out of. This theory is not widely accepted today, since Saturn's rings are thought to be unstable over periods of millions of years and therefore of relatively recent origin.
While the largest gaps in the rings, such as the Cassini division and Encke division, could be seen from Earth, the Voyager spacecrafts discovered the rings to have an intricate structure of thousands of thin gaps and ringlets. This structure is thought to arise from the gravitational pull of Saturn's many moons in several different ways. Some gaps are cleared out by the passage of tiny moonlets such as Pan, many more of which may yet be undiscovered, and some ringlets seem to be maintained by the gravitational effects of small shepherd satellites such as Prometheus and Pandora. Other gaps arise from resonances between the orbital period of particles in the gap and that of a more massive moon further out; Mimas maintains the Cassini division in this manner. Still more structure in the rings actually consists of spiral waves raised by the moons' periodic gravitational perturbations.
Data from the Cassini space probe indicates that the rings of Saturn possess their own atmosphere, independent of that of the planet itself. The atmosphere is composed of molecular oxygen gas (O2) and is thought to be a product of the disintegration of water ice from the rings into its components, oxygen and hydrogen.
Spokes of the Rings Until 1980, the structure of the rings of Saturn was explained exclusively as the action of gravitational forces. The Voyager spacecraft found radial features in the B ring, called spokes, which could not be explained in this manner, as their persistence and rotation around the rings were not consistent with orbital mechanics. The spokes appear dark against the lit side of the rings, and light when seen against the unlit side. It is assumed that they are connected to electromagnetic interactions, as they rotate almost synchronously with the magnetosphere of Saturn. However, the precise mechanism behind the spokes is still unknown.
Twenty-five years later, Cassini observed the spokes again. They appear to be a seasonal phenomenon, disappearing in the Saturnian midwinter/midsummer and reappearing as Saturn comes closer to equinox. The spokes were not visible when Cassini arrived at Saturn in early 2004. Some scientists speculated that the spokes would not be visible again until 2007, based on models attempting to describe spoke formation. Nevertheless, the Cassini imaging team kept looking for spokes in images of the rings, and the spokes reappeared in images taken September 5, 2005. Natural Satellites Saturn has a large number of moons. The precise figure will never be certain as the orbiting chunks of ice in Saturn's rings are all technically moons, and it is difficult to draw a distinction between a large ring particle and a tiny moon. Seven of the moons are massive enough to have collapsed into a spheroid under their own gravitation. These are compared to Earth's moon in the table below. Saturn's most noteworthy moon is Titan, the only moon in the solar system to have a dense atmosphere.
Due to the tidal forces of Saturn, the moons are currently not at the same position as they were when they were first formed. Saturn is currently known to have 47 moons, many of which were discovered very recently, and 3 suspected moons. However, a precise number of moons can never be given, as there is no objective dividing line between the anonymous orbiting chunks of ice in Saturn's ring system and the larger chunks of ice that have already been named as moons.
* Before the Space Age, 9 moons were known to orbit Saturn.
* In 1980, the Voyager space probes discovered 9 more moons in the inner Saturnian system.
* A survey starting in late 2000 found 12 new moons orbiting Saturn at a great distance in orbits that suggest they are fragments of larger bodies captured by Saturn's gravitational pull (Nature vol. 412, p.163-166).
* The Cassini mission, which arrived at Saturn in the summer of 2004, discovered three small moons in the inner Saturnian system. In addition three other moons in the F Ring are suspected, two of which remain unconfirmed. This increased the suspected number of moons to 37.
* On November 16, 2004, Cassini scientists announced that the structure of Saturn's rings indicates the presence of several more moons orbiting within the rings, but only one (Daphnis) has been visually confirmed so far.
* On May 3, 2005, astronomers using the Mauna Kea Observatory announced the discovery of 12 more small outer moons.
* On May 6, 2005, the Cassini imagining team announced the discovery of a small moon orbiting within the rings, Daphnis (S/2005 S 1).
The spurious satellite Themis, "discovered" in 1905, does not exist. The Saturnian moons are listed here by orbital period, from shortest to longest. Moons massive enough for their surfaces to have collapsed into a spheroid are highlighted in light purple. Titan, which is planetary in size, has darker highlighting. The irregular (captured) moons are indicated in grey. Name (spheroidal moons in bold)
(Pronunciation key) | Diameter (km) | Mean orbital
radius (km) | Orbital period (days) | Position | Discovered |
|---|
| XVIII | Pan | pan' | 20 (equator) | 133,583 | 0.576(1) | in Encke Division | 1990 | | XXXV | Daphnis | daf'-nəs | ~7 | 136,505(8) | 0.59537(1) | in Keeler Gap | 2005 | | XV | Atlas | at'-ləs | 33 (37 � 34 � 27) | 137,670 | 0.603(1) | outer A Ring shepherd | 1980 | | XVI | Prometheus | prə-mee'-thee-əs | 106 (148 � 100 � 68) | 139,350 | 0.614(1) | inner F Ring shepherds | 1980 | | | S/2004 S 6(2) | | ~5 | 140,000 | 0.61 | 2004 | | | S/2004 S 4(2) | | ~5 | 140,100 | 0.619(1) | 2004 | | | S/2004 S 3(2) | | ~5 | 140,580 | 0.62095 | outer F Ring Shepherds | 2004 | | XVII | Pandora | pan-dor'-ə | 87 (110 � 88 � 62) | 141,520 (3) | 0.6285(7) | 1980 | | XI | Epimetheus | ep'-ə-mee'-thee-əs | 119 (138 � 110 � 110) | 151,422(7) | 0.6956(1) | co-orbitals | 1980 | | X | Janus | jay'-nəs | 179 (194 � 190 � 154) | 151,472(7) | 0.6960(1) | 1966 | | I | Mimas | mye'-məs | 397 (418 � 392 � 383) | 185,404(3) | 0.942422(4) | | 1789 | | XXXII | Methone | mə-thoe'-nee | 3 | 194,000 | 1.01(1) | | 2004 | | XXXIII | Pallene | pə-lee'-nee | 4 | 211,000 | 1.14(1) | | 2004 | | II | Enceladus | en-sel'-ə-dəs | 499 (512 � 494 � 489) | 237,950(3) | 1.370218(4) | In the thick of E ring | 1789 | | XIII | Telesto | tə-les'-toe | 23 (30 � 25 � 15) | 294,619(3) | 1.887802(4) | leading Tethys trojan | 1980 | | III | Tethys | tee'-thəs | 1060 (1072 � 1056 � 1052) | | 1684 | | XIV | Calypso | kə-lip'-soe | 21 (30 � 16 � 16) | trailing Tethys trojan | 1980 | | XII | Helene | hel'-ə-nee | 33 (36 � 32 � 30) | 377,396(3) | 2.736915(4) | leading Dione trojan | 1980 | | IV | Dione | dye-oe'-nee | 1118 | | 1684 | | XXXIV | Polydeuces | pol'-ee-dew'-seez | 13 | trailing Dione trojan | 2004 | | V | Rhea | ree'-ə | 1528 | 527,108(5) | 4.518212(5) | | 1672 | | VI | Titan | tye'-tən | 5151 | 1,221,930(3) | 15.94542 | | 1655 | | VII | Hyperion | hye-peer'-ee-ən | 292 (360 � 280 � 225) | 1,481,010(3) | 21.27661 | | 1848 | | VIII | Iapetus | eye-ap'-ə-təs | 1436 | 3,560,820 | 79.3215(1) | | 1671 | | XXIV | Kiviuq | kee'-vee-oek | ~16 | 11,333,200(5) | 450.444(5) | Inuit group | 2000 | | XXII | Ijiraq | ee'-yə-raak | ~12 | 11,372,000(5) | 452.760(5) | 2000 | | IX | Phoebe | fee'-bee | 220 (230 � 220 � 210) | 12,944,300 | -549.834(1,6) | Norse group | 1899 | | XX | Paaliaq | paw'-lee-aak | ~22 | 14,923,800(5) | 680.667(5) | Inuit group | 2000 | | XXVII | Skathi | skaadh'-ee | ~8 | 15,576,200(5) | -725.784(4,6) | Norse (Skathi) Group | 2000 | | XXVI | Albiorix | al'-bee-or'-əks | ~32 | 16,401,600(5) | 784.226(5) | Gallic group | 2000 | | | S/2004 S 11 | - | ~6 | 16,898,400(5) | 820.130(5) | Inuit group | 2004 | | XXVIII | Erriapo | err'-ee-ap'-oe | ~10 | 17,408,700(5) | 857.556(5) | Gallic group | 2000 | | XXIX | Siarnaq | see'-ar-naak | ~40 | 17,905,700(5) | 894.542(5) | Inuit group | 2000 | | | S/2004 S 13 | - | ~6 | 18,056,300(5) | -905.848(4,6) | Norse group | 2004 | | XXI | Tarvos | tar'-vəs | ~15 | 18,160,200(5) | 913.685(5) | Gallic group | 2000 | | XXV | Mundilfari | moon'-dəl-fair'-ee | ~7 | 18,360,100(5) | -928.806(4,6) | Norse group | 2000 | | | S/2004 S 17 | - | ~4 | 19,099,200(5) | -985.453(4,6) | 2004 | | XXXI | Narvi | nar'-vee | ~7 | 19,370,700(5) | -1006.541(4,6) | 2003 | | | S/2004 S 15 | - | ~6 | 19,372,200(5) | -1006.659(4,6) | Norse (Skathi) group | 2004 | | | S/2004 S 10 | - | ~6 | 19,618,400(5) | -1025.908(4,6) | Norse group | 2004 | | XXIII | Suttungr | soot'-oong-ər | ~7 | 19,666,700(5) | -1029.703(4,6) | 2000 | | | S/2004 S 12 | - | ~5 | 19,905,900(5) | -1048.541(4,6) | Norse group | 2004 | | | S/2004 S 18 | - | ~7 | 19,958,700(5) | -1052.722(4,6) | Norse (Skathi) group | 2004 | | | S/2004 S 9 | - | ~5 | 20,290,800(5) | -1079.099(4,6) | Norse (Skathi) group | 2004 | | | S/2004 S 14 | - | ~6 | 20,303,300(5) | -1080.099(4,6) | Norse group | 2004 | | | S/2004 S 7 | - | ~6 | 20,576,700(5) | -1101.989(4,6) | 2004 | | XXX | Thrymr | thrim'-ər | ~7 | 20,810,300(5) | -1120.809(4,6) | 2000 | | | S/2004 S 16 | - | ~4 | 22,610,700(5) | -1269.362(4,6) | 2004 | | XIX | Ymir | ee'-mər | ~18 | 23,174,600(5) | -1317.137(4,6) | 2000 | | | S/2004 S 8 | - | ~6 | 23,608,900(5) | -1354.342(4,6) | 2004 |
Specifications Orbital Characteristics Semi-Major Axis 1,426,725,413 km (9.537 070 32 AU)
Orbital Circumference 8.958 Tm (59.879 AU)
Eccentricity 0.054 150 60
Perihelion 1,349,467,375 km (9.020 632 24 AU)
Aphelion 1,503,983,449 km (10.053 508 40 AU)
Orbital Period 10,756.1995 days (29.45 a)
Synodic Period 378.10 days
Avg. Orbital Speed 9.639 km/s
Max. Orbital Speed 10.183 km/s
Min. Orbital Speed 9.137 km/s
Inclination 2.484 46� (5.51� to Sun's equator)
Longitude of the Ascending Node 113.715 04�
Argument of the Perihelion 338.716 90�
Number of Satellites 47 confirmed Physical Characteristics Equatorial Diameter 120,536 km (9.449 Earths)
Polar Diameter 108,728 km (8.552 Earths)
Oblateness 0.097 96
Surface Area 4.27�1010 km2 (83.703 Earths)
Volume 7.46�1014 km3 (688.79 Earths)
Mass 5.6846�1026 kg (95.162 Earths)
Mean Density 0.6873 g/cm3 (less than water)
Equatorial Gravity 8.96 m/s2 (0.914 gee)
Escape Velocity 35.49 km/s
Rotation Period 0.444 009 259 2 days (10 h 39 min 22.400 00 s)
Rotation Velocity 9.87 km/s = 35,500 km/h (at the equator)
Axial Tilt 26.73�
Right Ascension of North Pole 40.59� (2 h 42 min 21 s)
Declination 83.54�
Albedo 0.47
Avg. cloudtop Temp. 93 K
Min. Surface Temp. 82 K
Mean Surface Temp. 143 K
Max. Surface Temp. N/A K
Adjective Saturnian Atmospheric Characteristics Atmospheric Pressure 140 kPa
Hydrogen >93%
Helium >5%
Methane 0.2%
Water Vapor 0.1%
Ammonia 0.01%
Ethane 0.0005%
Phosphine 0.0001% ** Information provided by Wikipedia, the free online encyclopedia. **
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