Large celestial bodies in orbit around a star, composed of rock, metal, or gas.

The nine planets in the solar system are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.

The inner four, called the "terrestrial planets" are small and rocky, and include the planet earth.

The outer planets, with the exception of Pluto, are called the major planets, and consist of large balls of rock, liquid, and gas; the largest is Jupiter, which contains a mass equivalent to 70% of all the other planets combined.

Planets do not produce light, but reflect the light of their parent star.

The planets are illustrated at the sight indicated below and links are available for more details about their Greek and Latin myths, symbolisms (system of symbols), and scientific information.

Click on this link for significant images and more detailed information about planets.

Passively drifting and wandering in the sky unit.

Mercury, Venus, Earth, and Mars.

The orbits and positions of the planets or "wanderers" could not be accurately accounted for before the invention of the telescope although star positions were known.

Understanding came with the revolutionary work of Galileo, Brahe, and Kepler which, together with Newton's contributions, finally swept away the Greek concept of an earth-centered universe and established the present model of the solar system.

The Greeks had simplified celestial mechanics according to the simple doctrine that "matter behaves according to nature."