Saturn (planet)

Saturn

Saturn in natural color approaching equinox, photographed by Cassini in July 2008. The little white dot in the bottom left corner is Titan.
Designations
Pronunciation	i/ˈsætərn/
Named after	Saturn
Adjectives	Saturnian, Cronian
Orbital characteristics
Epoch J2000.0
Aphelion	10.086 AU (1.509 billion km)
Perihelion	9.024 AU (1.350 billion km)
Semi-major axis	9.5549 AU (1.429 billion km)
Eccentricity	6998555500000000000♠0.05555
Orbital period	7001294571000000000♠29.4571 yr 7008929596608000000♠10,759.22 d 7004244910700000000♠24,491.07 Saturnian solar days
Synodic period	378.09 days
Average orbital speed	9.69 km/s (6.02 mi/s)
Mean anomaly	7000553304279467243♠317.020°
Inclination	6998433756207022639♠2.485240° to ecliptic 5.51° to Sun's equator 0.93° to invariable plane
Longitude of ascending node	7000198382849427935♠113.665°
Argument of perihelion	7000592350785492860♠339.392°
Known satellites	62 with formal designations; innumerable additional moonlets.
Physical characteristics
Mean radius	58,232 ± 6 km (36,184 ± 4 mi)
Equatorial radius	60,268 ± 4 km (37,449 ± 2 mi) 7000944920000000000♠9.4492 Earths
Polar radius	54,364 ± 10 km (33,780 ± 6 mi) 7000855209999999999♠8.5521 Earths
Flattening	6998979600000000000♠0.09796±0.00018
Surface area	4.27×1010 km2 (1.65×1010 sq mi) 7001837030000000000♠83.703 Earths
Volume	8.2713×1014 km3 (1.9844×1014 cu mi) 7002763590000000000♠763.59 Earths
Mass	5.6836×1026 kg (1.2530×1027 lb) 7001951590000000000♠95.159 Earths
Mean density	0.687 g/cm3 (0.0248 lb/cu in) (less than water)
Surface gravity	10.44 m/s2 (34.3 ft/s2) 1.065 g
Moment of inertia factor	6999210000000000000♠0.210(estimate)
Escape velocity	35.5 km/s (22.1 mi/s)
Sidereal rotation period	10.55 hours (10 hr 33 min)
Equatorial rotation velocity	9.87 km/s (6.13 mi/s; 35,500 km/h)
Axial tilt	26.73°(to orbit)
North pole right ascension	2h 42m 21s; 40.589°
North pole declination	83.537°
Albedo	0.342 (Bond) 0.499 (geometric)
Surface temp. min mean max 1 bar 134 K (−139 °C) 0.1 bar 84 K (−189 °C)
Apparent magnitude	+1.47 to −0.24
Angular diameter	14.5″ to 20.1″ (excludes rings)
Atmosphere
Scale height	59.5 km (37.0 mi)
Composition by volume	by volume: ≈ 96% hydrogen (H 2) ≈ 3% helium (He) ≈ 0.4% methane (CH 4) ≈ 0.01% ammonia (NH 3) ≈ 0.01% hydrogen deuteride (HD) 0.0007% ethane (C 2H 6) Ices: ammonia (NH 3) water (H 2O) ammonium hydrosulfide (NH 4SH)

by volume:

Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius about nine times that of Earth. Although it has only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive. Saturn is named after the Roman god of agriculture; its astronomical symbol (♄) represents the god's sickle.

Saturn's interior is probably composed of a core of iron–nickel and rock (silicon and oxygen compounds). This core is surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium, and finally outside the Frenkel line a gaseous outer layer. Saturn has 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 Saturn's planetary magnetic field, which is weaker than Earth's, but has a magnetic moment 580 times that of Earth due to Saturn's larger size. Saturn's magnetic field strength is around one-twentieth of Jupiter's. 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 (500 m/s), higher than on Jupiter, but not as high as those on Neptune.