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Saturn

Saturn has been known as a bright, mobile star since prehistory. Its strange, shifting shape puzzled observers until Christiaan Huygens proposed the idea that Saturn had a ring around it. This explained why it appeared to have bumps or handles which disappeared at times (when the rings were edge-on to the Earth).

Saturn is the second largest planet in the Solar System. Despite this, it has an overall specific gravity of  0.7, which makes it less dense than water. This is due to the fact that Saturn is truly a gas giant. It has almost no rocky bits in its interior, only ice and gas. Like Jupiter, it has a middle of liquid metallic Hydrogen, and thus its own magnetic field. It also produces its own heat, again like Jupiter, radiating back more than the heat it gets from the Sun. Due to its gassy form, Saturn has been squashed noticeably by its own gravity. It is oblate.

Saturn has been visited by 3 spacecraft to date, Pioneer 11, Voyager 1, Voyager 2, and another craft, Cassini, is planned to pass it in the near future. These craft have observed Saturn’s multiple rings covered in ‘spokes’, smudges on the rings, small spots similar to Jupiter’s great spot, and 18 moons orbiting the planet. They found that the rings are made up of lots of ice and dust and that the gaps in the rings were formed by the passage of Saturn’s moons, most notably Mimas, through the rings themselves. Meteors and stuff breaking up against these moons keeps the rings supplied with dust.

Diameter

120, 500 km

Mass

5.7 × 1026 kg

Mean Distance from sun

1,429,400,000 km

Mean Density

0.69 g/cm3

Rotational Period

0.44 Earth days

Orbital Period

29.5 Earth years

Mean Orbital Velocity

9.67 km/s

Atmosphere

95% hydrogen, 5% helium

Average Surface Temperature

-125°C

Equatorial Surface Gravity

 8.96 m/s2