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 Saturns multiple rings covered
in spokes, smudges on the rings, small spots similar to Jupiters
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 Saturns moons, most notably Mimas, through
the rings themselves. Meteors and stuff breaking up against these moons
keeps the rings supplied with dust.
Diameter
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120, 500 km
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Mass
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5.7 × 1026 kg
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Mean Distance from sun
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1,429,400,000 km
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Mean Density
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0.69 g/cm3
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Rotational Period
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0.44 Earth days
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Orbital Period
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29.5 Earth years
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Mean Orbital Velocity
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9.67 km/s
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Atmosphere
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95% hydrogen, 5% helium
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Average Surface Temperature
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-125°C
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Equatorial Surface Gravity
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�8.96 m/s2
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