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The planet Saturn with aurora

Saturn with aurorae. Credit: NASA, ESA, J. Clarke (Boston University), and Z. Levay (STScI)

Named after the Roman god of agriculture, Saturn is the sixth planet from the Sun and the second largest planet in the solar system after Jupiter. Like its larger neighbour, Saturn’s massive hydrogen and helium atmosphere are what define it as a gas giant planet, though thousands of kilometers below the surface, there probably lies a metal and silicate (rock) core.

At over one billion kilometers distant, Saturn is the farthest planet from the Earth to have been discovered before the advent of the telescope, however it is easily visible to the naked eye, and occasionally rivals Alpha Centauri (the closest naked-eye visible star to Earth) for brightness.

Of course, Saturn’s most spectacular feature is its system of rings, which stretch to over 120,000 kilometers above the planet’s equator. The main rings are composed of innumerable fragments of almost pure water ice, and range in size from about a centimeter to about ten meters across.

Quick Stats

  • Classification:  Gas Giant Planet
  • Equatorial Radius:  60,268 km   (9.45 x Earth)
  • Mass: 5.6846×1026 kg   (95.152 x Earth)
  • Sidereal Rotation Period: 58.6 days
  • Orbital Period: 10 hr 3 min
  • Orbital Distance: 9.58 AU (1,433,449,370 km)
  • Inclination: 2.5°
  • Eccentricity: 0.06
  • Axial Tilt: 26.73°
  • Density: 0.687 g/cm3
  • Surface Gravity: 1.065 g
  • Temperature: -139°C at Earth atmospheric pressure
  • Moons: 62, plus innumerable moonlets that compose the ring system

Factoids

  • Saturn is the second largest planet after Jupiter, however it only has around three-tenths of the larger planet's mass.
  • Saturn's average density is around 30% less than water, meaning the planet would float - if you could find a bathtub large enough!
  • Due to its rapid rate of spin, Saturn is not spherical but is flattened at the poles - a shape known as an oblate spheroid.
  • In Saturn's case, its equatorial diameter is around 8,000 kilometers more than the distance from pole to pole.
  • At over one billion kilometers from Earth, Saturn is the farthest planet that can be reliably spotted with the naked eye. At its brightest, it rivals Alpha Centauri.
  • Saturn's rings are more than 200 times the planet's radius across, but they are only around 10-20 meters thick.
  • Like Jupiter, Saturn's core is thought to be surrounded by a layer of liquid, metallic hydrogen.
  • Saturn has a magnetic field, but it is significantly weaker than Jupiter's. In fact, it is even slightly weaker than the Earth's magnetic field.
  • Saturn's largest moon, Titan, is larger than the planet Mercury, and is the only moon in the solar system to have a significant atmosphere.
  • Apart from the Earth, Titan is the only solar system body to have liquid lakes on its surface - though in Titan's case these are not lakes of liquid water, but rather liquid methane.
  • Saturn rotates faster at the equator than it does at the poles. This is known as differential rotation.
  • There is a mysterious hexagon pattern in the clouds at Saturn's north pole. While it is not completely understood, many think it is caused by a standing-wave pattern in the planet's atmosphere.
  • While Saturn's south pole does not show a similar hexagonal feature as the north pole, there is a giant rotating storm about the size of the Earth, with winds around 550 km/h.

Planets Earth and Saturn to Scale

Planets Earth and Saturn to scale

Earth and Saturn to scale. Credit NASA / JPL

The Planet Saturn