The term planet has its origins in the ancient Greek word for the wanderer and means exactly that; planet is an orbiting the sun celestial body that has enough gravity to rotate and have a spherical form but not enough to cause nuclear fusion and thus radiate heat and light.
The planets of our solar system are divided into two types; those with low density gas giants (Jupiter, Saturn, Uranus, and Neptune) and the solid, smaller terrestrials (Mercury, Venus, Earth, and Mars) with a kind of atmosphere around them. |
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