THE SATURN PLANET N ITS MOONS = This article is about the planet. For other uses, see Saturn (disambiguation). Page semi-protected Saturn Astronomical symbol for Saturn The planet Saturn Saturn in natural color, photographed by Cassini, 2004 Designations Pronunciation Listeni/ˈsætərn/[1] Adjectives Saturnian, Cronian Orbital characteristics[5][a] Epoch J2000.0 Aphelion 1513325783 km (10.11595804 AU) Perihelion 1353572956 km (9.04807635 AU) Semi-major axis 1433449370 km (9.5820172 AU) Eccentricity 0.055723219 Orbital period 10759.22 d 29.4571 yr 24491.07 Saturn solar days[2] Synodic period 378.09 days[3] Average orbital speed 9.69 km/s[3] Mean anomaly 320.346750° Inclination 2.485240° to Ecliptic 5.51° to Suns equator 0.93° to invariable plane[4] Longitude of ascending node 113.642811° Argument of perihelion 336.013862° Known satellites 62 with formal designations; innumerable additional moonlets.[3] Physical characteristics Mean radius 58232±6 km[6][b] Equatorial radius 60268±4 km[6][b] 9.4492 Earths Polar radius 54364±10 km[6][b] 8.5521 Earths Flattening 0.09796±0.00018 Surface area 4.27×1010 km2[b][7] 83.703 Earths Volume 8.2713×1014 km3[3][b] 763.59 Earths Mass 5.6846×1026 kg[3] 95.152 Earths Mean density 0.687 g/cm3[3][b] (less than water) Surface gravity 10.44 m/s²[3][b] 1.065 g Escape velocity 35.5 km/s[3][b] Sidereal rotation period 10.57 hours[8] (10 hr 34 min) Equatorial rotation velocity 9.87 km/s[b] 35500 km/h Axial tilt 26.73°[3] North pole right ascension 2h 42m 21s 40.589°[6] North pole declination 83.537°[6] Albedo 0.342 (Bond) 0.47 (geometric)[3] Surface temp. min mean max 1 bar level 134 K (-139°C)[3] 0.1 bar 84 K[3] Apparent magnitude +1.47 to −0.24[9] Angular diameter 14.5″ to 20.1″[3] (excludes rings) Atmosphere[3] Scale height 59.5 km Composition ≈96% hydrogen (H2) ≈3% helium (He) ≈0.4% methane (CH4) ≈0.01% ammonia (NH3) ≈0.01% hydrogen deuteride (HD) 0.0007% ethane (C2H6) Ices: ammonia (NH3) water (H2O) ammonium hydrosulfide (NH4SH) Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Named after the Roman god of agriculture, its astronomical symbol (♄) represents the gods sickle. Saturn is a gas giant with an average radius about nine times that of Earth.[10][11] While only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive. Saturns interior is probably composed of a core of iron, nickel and rock (silicon and oxygen compounds), surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium and an outer gaseous layer.[15] The planet exhibits a pale yellow hue due to ammonia crystals in its upper atmosphere. Electrical current within the metallic hydrogen layer is thought to give rise to Saturns planetary magnetic field, which is weaker than Earths magnetic field but has a magnetic moment 580 times that of the Earth due to Saturns larger body radius. Saturns magnetic field strength is around one-twentieth the strength of Jupiters.[16] The outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h (1,100 mph), faster than on Jupiter, but not as fast as those on Neptune.[17] Saturn has a prominent ring system that consists of nine continuous main rings and three discontinuous arcs, composed mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-two[18] known moons orbit the planet; fifty-three are officially named. This does not include the hundreds of moonlets comprising the rings. Titan, Saturns largest and the Solar Systems second largest moon, is larger than the planet Mercury and is the only moon in the Solar System to retain a substantial atmosphere Saturn is classified as a gas giant because the exterior is predominantly composed of gas and it lacks a definite surface, although it may have a solid core.[20] The rotation of the planet causes it to take the shape of an oblate spheroid; that is, it is flattened at the poles and bulges at the equator. Its equatorial and polar radii differ by almost 10%: 60,268 km versus 54,364 km, respectively.[3] Jupiter, Uranus, and Neptune, the other gas giants in the Solar System, are also oblate but to a lesser extent. Saturn is the only planet of the Solar System that is less dense than water—about 30% less.[21] Although Saturns core is considerably denser than water, the average specific density of the planet is 0.69 g/cm3 due to the gaseous atmosphere. Jupiter has 318 times the Earths mass,[22] while Saturn is 95 times the mass of the Earth,[3] Together, Jupiter and Saturn hold 92% of the total planetary mass in the Solar System.
Posted on: Sat, 05 Jul 2014 08:36:20 +0000
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