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Saturn (planet)


Larger image and caption
Orbital characteristics
Mean radius1,426,725,400 km km
Revolution period29y 167d 6.7h
Synodic period378.1 days
Avg. Orbital Speed9.6724 km/s
Number of satellitess30
Physical characteristics
Equatorial diameter120,536 km
Surface area4.38×1010 km2
Mean density0.69 g/cm3
Surface gravity8.96 m/s2
Rotation period
10h 13m 59s
Rotation period
10h 39m 25s
Axial tilt26.73°
Escape Speed35.49 km/s
Avg. Cloudtop temp93K
Surface temp
82K143KN/A K
Atmospheric characteristics
Atmospheric pressure140 kPa
Water vapor0.1%


Table of contents
1 Physical characteristics
2 The exploration of Saturn
3 Saturn's rings
4 Saturn's moons
5 Front Row Seats

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 not so much so. Saturn is also the least dense of the Solar System's planets with an average specific density of 0.69, significantly less than water. 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 atmosphere exhibits a banded pattern similar to Jupiter's, but Saturn's bands are much fainter and they're also much wider near the equator. Saturn's 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 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 exploration of Saturn

Saturn was first visited by Pioneer 11 in 1979 and later by Voyager 1 and Voyager 2. The Cassini, now on its way, will arrive in 2004.

Saturn's rings


The riddle of the rings was not solved until 1655 by Christiaan Huygens, using a telescope much more powerful than the ones available to Galileo in his time. Leo Allatius, a theologian at the time, suggested that the ring may be the foreskin of Jesus Christ, ascended into the heavens.



Saturn's moons


Saturn's natural satellites
Name Diameter (km) Mass (kg) Mean orbital
radius (km)
Orbital period  
Pan 20 Unknown 133,583 0.575 days
Atlas 30 (40 × 20) Unknown 137,670 0.6019 days
Prometheus 91 (145 × 85 × 62) 2.70×1017 139,350 0.6130 days
Pandora 84 (114 × 84 × 62) 2.20×1017 141,700 0.6285 days
Epimetheus 115 (144 × 108 × 98) 5.60×1017 151,422 0.6942 days Co-orbital
Janus 178 (196 × 192 × 150) 2.01×1018 151,472 0.6945 days
Mimas 392 3.80×1019 185,520 0.942422 days  
Enceladus 498 7.30×1019 238,020 1.370218 days
Tethys 1060 6.22×1020 294,660 1.887802 days Co-orbital
Telesto 29 (34 × 28 × 36) Unknown 294,660 1.887802 days
Calypso 26 (34 × 22 × 22) Unknown 294,660 1.887802 days
Dione 1120 1.05×1021 377,400 2.736915 days Co-orbital
Helene 33 (36 × 32 × 30) Unknown 377,400 2.736915 days
Rhea 1530 2.49×1021 527,040 4.5175 days  
Titan 5150 1.35×1023 1,221,830 15.94542 days
Hyperion 286 (410 × 260 × 220) 1.77×1019 1,481,100 21.27661 days
Iapetus 1460 1.88×1021 3,561,300 79.33018 days
Phoebe 220 4.00×1018 12,952,000 550.48 days

Front Row Seats

Saturn's Opposition Periods 2001-2005
Date of Opposition Distance to Earth (AU) Angular diameter
December 3, 2001 8.08 20.6 arcsec
December 17, 2002 8.05 20.7 arcsec
December 31, 2003 8.05 20.7 arcsec
January 13, 2005 8.08 20.6 arcsec

The Solar System

Sun - Mercury - Venus - Earth - Mars - Asteroids - Jupiter - Saturn - Uranus - Neptune - Pluto - Comets - Kuiper belt - Oort cloud