The+Gas+Planets

Jupiter, Saturn, Uranus, Neptune
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 * Jupiter**

Number of satellites: 63 Rings: No Diameter: Approx 140,000 km Orbital period: 11.9 years Composition: Mainly hydrogen and helium

Note: density of Jupiter (calculated as mass / volume): 1 330kg/m -3. This compares to Earth's density (mass: 59 740x10 20 kg; volume: 1.082x10 21 m 3 ) of 5 521kg/m -3. This is typical of the difference between the inner and outer planets, and the latter are made up of hydrogen and helium (which have a relatively low density even when compressed into liquids in planetary interiors) and with an icy/rocky core (note that in cosmological terms, "icy" materials can include both frozen and liquid substances (even relatively hot liquids) while 'rocky' materials, can include solids and liquids. The distinguishing features of these terms are really the densities, with icy materials less dense than rocky materials (although more dense than hydrogen and helium).

[|Jupiter - BBC material]


 * Saturn**

Number of satellites: 56 Rings: Yes - most complex in solar system Diameter: Approx 120,000 km Orbital period: 29.5 years Composition: Mainly hydrogen and helium (probably a liquid core)

[|Saturn - BBC material]


 * Uranus**

Number of satellites: 27 Rings: Yes Diameter: Approx 51,000 km Orbital period: 84 years Composition: Approximately half hydrogen and helium, half icy/rocky core. Also methane.

Axis of rotation is inclined to almost the plane of orbit, so that Uranus "rolls" around the Sun.

[|Uranus - BBC material]


 * Neptune**

Number of satellites: 13 Rings: Yes, very thin and faint Diameter: Approx 49,000 km Orbital period: 164 years Composition: hydrogen and helium with over half icy/rocky core. Also methane.

[|Neptune - BBC material]