Planet - Definition of Planet

Definition: planet: A planet is a spherical ball of rock and/or gas that orbits a star. The Earth is a planet. Our solar system has nine planets. These planets are, in order of increasing average distance from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. The only object visited by humans other than the planet Earth is the Moon, which is not a planet. It is a satellite.