Planet

A planet in common parlance is a large object in orbit around a star that is not a star itself. The name comes from the Greek term πλανήτης, planētēs, meaning "wanderer", as ancient astronomers noted how certain lights moved across the sky in relation to the other stars. The International Astronomical Union lists nine planets in our solar system, based on historical consensus. Since the term planet has no scientific definition, many astronomers contest that figure, with some saying it should be lowered to eight (removing Pluto from the list), and others claiming it should be raised to fifteen, about twenty, or even dozens, depending on the definition used.

See also

• Definition of planet
• Planetary habitability
• Planetary science
• Planets in science fiction
• Prograde and retrograde motion
• Skies of other planets