Saturn Facts

Discoverer: Unknown
Spacecraft Encounters: Pioneer 11 (1979);
Voyager 1 & 2 (1980, 1981)
Cassini - Huygens (2004)
Mean Distance from the Sun: 9.539 AU
1, 427,000,000 km /886,700,000 mi
Length of Year: 29.46 Earth years
Rotation Period: 10.66 hours
Mean Orbital Velocity: 9.64 km/s (6 mi/s)
Inclination of Axis: 26.73 degrees
Diameter: 120,536 km (74,901 mi)
Number of Observed Satellites: >25

Comparisons With Earth:

Diameter: 9.4 X Earth's
Average Distance from the Sun: 9.5 X Earth's
Mass: 95 X Earth's
Density: 0.13 X Earth's

The Rings of Saturn

In 1610, Galileo observed the peculiar appearance of Saturn, but was not able to recognize the true shape of the features on either side of the planet. It was not until almost 50 years later that the astronomer Christian Huygens discovered that the shapes were really rings.

Saturn Ring Plane Crossing, 1995

One obstacle to the recognition of Saturn's rings was that they are seen edge-on from Earth every 15 years, and thus seemed to disappear.

Photo#PRC95-31 from the Space Telescope Science Institute.

Structure In The Rings

By 1675, Jean Dominique Cassini had discovered a gap in the rings that now bears his name (the Cassini Division). Numerous other gaps and rings were discovered by Earth-based telescopes through the 1970s, so that by the time Pioneer 11 arrived in 1979, the light and dark bands had their own set of names.

Voyager 2 Image showing Cassini Division

NASA Press Release #P-23942C

Pioneer 11 close-up of Saturn's ring structure.

Saturn closeup

NASA Press Release #79-HC-434


All information and images on this page were obtained from the National Air and Space Museum.

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