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Classification of the Solar System





Mercury  Venus  Earth  Mars  Jupiter  Saturn   Uranus  Neptune  Pluto
(Planets are not to scale.)
Classification of

the Solar System

The planets of the solar

system can be classified in different ways

  1. by size
  2. by composition (or what they are made of)
  3. by distance from the Sun
  4. by history (when they were discovered)
Classification by Size

  1. There are the small planets: Mercury, Venus, Earth, Mars and Pluto. These planets have diameters less than 13000

    kilometers. Mercury and Pluto are sometimes referred to as lesser

    planets (not to be confused with minor planets which is the official

    term for asteroids).

  2. There are also the giant planets: Jupiter, Saturn, Uranus and Neptune. The giant planets have diameters greater

    than 48000 kilometers. These planets are sometimes also called the

    gas giants.

Classification by composition

  • There are terrestrial, or rocky planets, the ones made up mostly of

    rock and metal. These planets are Mercury, Venus, Earth and Mars.

    The terrestrial planets are have relatively high densities, slow rotation, solid surfaces, no rings and few satellites.

  • Then there are the jovian or gas planets. These planets are Jupiter, Saturn,

    Uranus and Neptune.

    The gas planets are made up mostly of hydrogen and helium. They and

    usually have low densities, rapid rotation, deep atmospheres, rings and

    lots of satellites.

  • Pluto

    is an exception as it thought to be made up of a mixture of rocks and

    several kinds of “ices”. Scientists believe that most of these ices are

    that frozen gases and liquids such as methane and ammonia.


from the Sun



  • There are the classical planets: Mercury, Venus, Mars, Jupiter, and Saturn. These planets have been known since prehistorical times.

    They can all been seen from Earth without the use of binoculars or telescopes.

  • There are also the modern planets: Uranus, Neptune, Pluto.

    These have been discovered since the invention of telescopes since they are only visible with telescopes.

  • There is also Earth.

Resources Used
Astronomy for Kids
Small Worlds David Drew: Nelson, 1989
The Gas Giants David Drew: Nelson, 1989

Solar System Unit Glossary

Images from:

  Astronomy Picture

of the Day


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