Terrestrial Planets | Jovian Planets | Dwarf Planets |                                Planet Density | Planet Rotation
Jovian Planets

The next four planets are called the gas giants, or the Jovian planets (named after Jupiter). A gas giant is just what the name says - very big with a thick atmosphere. Most of the mass in the solar system (besides the mass of our enormous Sun) is found in these planets. The gas giants are mostly made up of hydrogen. A gas giant also does not have a solid surface. Instead, the gas that makes up the atmosphere is compressed into a liquid, and then into something that acts like a metal. We call this metallic hydrogen. The core is composed of rock and ice.

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    The fifth planet from the Sun

    Mass = 1.90e27 kg
    Diameter = 142,800 km
    Density = 1.314 g/cubic cm
    Jovian day = 9.8 Earth hours
    Distance from Sun = 5.2 AU

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    The sixth planet from the Sun

    Mass = 5.69e26 kg
    Diameter = 120,540 km
    Density = 0.69 g/cubic cm
    Saturnian day = 10.2 Earth hours
    Distance from Sun = 9.5 AU

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    The seventh planet from the Sun

    Mass = 8.69e25 kg
    Diameter = 51,488 km
    Density = 1.29 g/cubic cm
    Uranian day = 17.3 Earth hours
    Distance from Sun = 19.1 AU

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    The eighth planet from the Sun

    Mass = 1.024e26 kg
    Diameter = 48,599 km
    Density = 1.64 g/cubic cm
    Neptunian day = 16.03 Earth hours
    Distance from Sun = 30.0


The moons of the Jovian planets, such as Jupiter's moons Io and Europa, or Saturn's moon Titan, have densities typically 1-3 g/cm3 and are composed of a mix of rock and ice.  Since ice has a density of about 1 g/cm3 , this means that generally, the higher the density of the moon the greater the fraction of rock.

The montage below shows Jupiter's Galilean moons: Io, Europa, Callisto and Ganymede, in a size comparison with Earth and our Moon.