Saturn
The sixth planet from the Sun
The second-largest planet, Saturn is so light for its size that its average density is below that of water, and it spins fast enough, once in about ten and a half hours, to bulge visibly at the equator: it is the flattest of the planets. Like Jupiter it has no surface, only an atmosphere of hydrogen and helium under pale bands of cloud.
Its main rings span more than 270,000 km yet are mostly only about ten metres thick: billions of pieces of water ice, from grains to chunks the size of a house. They lie in the plane of its equator, so over its 29-year orbit they tip toward us and away again; seen edge-on from Earth in March 2025, they are opening again now.
Key figures
- Diameter
- 120,536 km, 9.45 × Earth
- Mass
- 95 × Earth
- Density
- 687 kg/m³, less than water
- Gravity at the 1-bar level
- 11.19 m/s², 1.14 × Earth's
- Rotation period
- 10 h 39 min 22 s
- One orbit of the Sun
- 29.45 years
- Mean distance from the Sun
- 1.432 billion km
- Temperature at the 1-bar level
- -139 °C
- Atmosphere
- 96.3% hydrogen, 3.25% helium
- Main rings
- 74,658 to 136,775 km from its centre
- Moons
- 293 (as of August 2026)