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Saturn is the most distant of the five planets known to ancient stargazers. In 1610, Italian Galileo Galilei was the first astronomer to gaze at Saturn through a telescope. To his surprise, he saw a pair of objects on either side of the planet, which he later drew as "cup handles" attached to the planet on each side. In 1659, Dutch astronomer Christiaan Huygens announced that this was a ring encircling the planet.

In 1675, Italian-born astronomer Jean Dominique Cassini discovered a gap between what are now called the A and B rings.

Like Jupiter, Uranus, and Neptune, Saturn is a gas giant. It is made mostly of hydrogen and helium. Its volume is 755 times greater than Earth's. Winds in the upper atmosphere reach 500 meters per second in the equatorial region. (In contrast, the strongest hurricane-force winds on Earth top out at about 110 meters per second.) These superfast winds, combined with heat rising from within the planet's interior, cause the yellow and gold bands visible in its atmosphere.

Saturn's ring system is the most extensive and complex in our solar system; it extends hundreds of thousands of kilometers from the planet. In fact, Saturn and its rings would just fit in the distance between Earth and the Moon. 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 seem to circle the planet at a different rate from that of the surrounding ring material. Some of the small moons orbit within the ring system as well. Material in the rings ranges in size from a few micrometers to several tens of meters.

Saturn has 34 known natural satellites (moons) and there are probably many more waiting to be discovered. The largest, Titan, is a bit bigger than the planet Mercury. 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 as well.

In addition to Titan, Saturn has many smaller icy satellites. From Enceladus, which shows evidence of surface changes, to Iapetus, with one hemisphere darker than asphalt and the other as bright as snow, each of Saturn's satellites is unique.

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. Images taken by NASA's Hubble Space Telescope show that Saturn's polar regions have aurorae similar to Earth's Northern and Southern Lights. 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: Unknown

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: 7.207 m/s2

English: 23.64 ft/s2

By Comparison: If you weigh 100 pounds on Earth, you would weigh 74 pounds on Saturn.


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: .0445 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.


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