A Hubble Space Telescope image of Saturn in true color.
A Hubble Space Telescope image of Saturn in true color.
Saturn was the most distant of the five planets known to the ancients. In 1610, Italian astronomer Galileo Galilei was the first to gaze at Saturn through a telescope. To his surprise, he saw a pair of objects on either side of the planet. He sketched them as separate spheres and wrote that Saturn appeared to be triple-bodied. Continuing his observations over the next few years, Galileo drew the lateral bodies as arms or handles attached to Saturn. In 1659, Dutch astronomer Christiaan Huygens, using a more powerful telescope than Galileo's, proposed that Saturn was surrounded by a thin, flat ring. In 1675, Italian-born astronomer Jean-Dominique Cassini discovered a 'division' between what are now called the A and B rings. It is now known that the gravitational influence of Saturn's moon Mimas is responsible for the Cassini Division, which is 4,800 kilometers (3,000 miles) wide.

Like Jupiter, Saturn is made mostly of hydrogen and helium. Its volume is 755 times greater than that of Earth. Winds in the upper atmosphere reach 500 meters (1,600 feet) per second in the equatorial region. (In contrast, the strongest hurricane-force winds on Earth top out at about 110 meters, or 360 feet, per second.) These super-fast winds, combined with heat rising from within the planet's interior, cause the yellow and gold bands visible in the atmosphere.

A Cassini spacecraft image of Titan's thick atmosphere.
A Cassini spacecraft image of Titan's thick atmosphere.
Saturn's ring system is the most extensive and complex in the so-lar system, extending hundreds of thousands of kilometers from the planet. In the early 1980s, NASA's two Voyager spacecraft revealed that Saturn's rings are made mostly of water ice, and they found 'braided' rings, ringlets, and 'spokes' - dark features in the rings that circle the planet at different rates from that of the surrounding ring material. Material in the rings ranges in size from a few micrometers to several tens of meters. Two of Saturn's small moons orbit within gaps in the main rings.

Saturn has 52 known natural satellites (moons) and there are probably many more waiting to be discovered. Saturn's largest satellite, Titan, is a bit bigger than the planet Mercury. (Titan is the second-largest moon in the solar system; only Jupiter's moon Ganymede is bigger.) Titan is shrouded in a thick, nitrogen-rich atmosphere that might be similar to what Earth's was like long ago. Further study of this moon promises to reveal much about planetary formation and, perhaps, about the early days of Earth. Saturn also has many smaller 'icy' satellites. From Enceladus, which shows evidence of recent (and ongoing) surface changes, to Iapetus, with one hemisphere darker than asphalt and the other as bright as snow, each of Saturn's satellites is unique.

Though Saturn's magnetic field is not as huge as Jupiter's, it is still 578 times as powerful as Earth's. Saturn, the rings, and many of the satellites lie totally within Saturn's enormous magnetosphere, the region of space in which the behavior of electrically charged particles is influenced more by Saturn's magnetic field than by the solar wind. Hubble Space Telescope images show that Saturn's polar regions have aurorae similar to Earth's. Aurorae occur when charged particles spiral into a planet's atmosphere along magnetic field lines.

Saturn: Facts & Figures
Discovered By
Known by the Ancients
Date of Discovery
Average Distance from the Sun
Metric: 1,426,725,400 km
English: 885,904,700 miles
Scientific Notation: 1.4267254 x 109 km (9.53707 A.U.)
By Comparison: 9.53707 x Earth
Perihelion (closest)
Metric: 1,349,467,000 km
English: 838,519,000 miles
Scientific Notation: 1.349467 x 109 km (9.021 A.U.)
By Comparison: 9.177 x Earth
Aphelion (farthest)
Metric: 1,503,983,000 km
English: 934,530,000 miles
Scientific Notation: 1.503983 x 109 km (10.054 A.U.)
By Comparison: 9.886 x Earth
Equatorial Radius
Metric: 60,268 km
English: 37,449 miles
Scientific Notation: 6.0268 x 104 km
By Comparison: 9.449 x Earth
Equatorial Circumference
Metric: 378,675 km
English: 235,298 miles
Scientific Notation: 3.78675 x 105 km
Metric: 827,130,000,000,000 km3
Scientific Notation: 8.2713 x 1014 km3
By Comparison: 763.6 x Earth
Metric: 568,510,000,000,000,000,000,000,000 kg
Scientific Notation: 5.6851 x 1026 kg
By Comparison: 95.16 x Earth
Metric: 0.70 g/cm3
By Comparison: 0.127 x Earth
Surface Area
Metric: 43,466,000,000 km2
English: 16,782,000,000 square miles
Scientific Notation: 4.3466 x 1010 km2
By Comparison: 85.22 x Earth
Equatorial Surface Gravity
Metric: 10.4* m/s2
English: 34.11 ft/s2
By Comparison: If you weigh 100 pounds on Earth, you would weigh 91 pounds on Saturn (at the equator). *Derived from a 1 bar radius of 60,268 km.
Escape Velocity
Metric: 127,760 km/h
English: 79,390 mph
Scientific Notation: 35,490 m/s
By Comparison: Escape velocity of Earth is 25,022 mph.
Sidereal Rotation Period (Length of Day)
0.44401 Earth days
10.656 hours
By Comparison: 0.445 x Earth
Sidereal Orbit Period (Length of Year)
29.4 Earth years
10755.7 Earth days
Mean Orbit Velocity
Metric: 34,821 km/h
English: 21,637 mph
Scientific Notation: 9,672.4 m/s
By Comparison: 0.865 x Earth
Orbital Eccentricity
By Comparison: 3.24 x Earth
Orbital Inclination to Ecliptic
2.484 degrees
Equatorial Inclination to Orbit
26.73 degrees
By Comparison: 1.14 x Earth
Orbital Circumference
Metric: 8,725,000,000 km
English: 5,421,000,000 miles
Scientific Notation: 8.725 x 109 km
By Comparison: 9.439 x Earth
Effective Temperature
Metric: -178 C
English: -288 F
Scientific Notation: 95 K
Atmospheric Constituents
Hydrogen, Helium
Scientific Notation: H2, He
By Comparison: Earth's atmosphere consists mostly of N2 and O2.
Additional Information:

Namesake: Roman god of agriculture


Saturn's Moons