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.

External links

• NinePlanets.org - tour of the solar system
• International Astronomical Union
• Solar System Live (an interactive orrery)
• Solar System Viewer (animation)
• Pictures of the solar system
• Renderings of the planets
• NASA Planet Quest
• Working definition of "planet" from IAU WGESP — the lower bound remained a matter of consensus in February 2003
• Dan Green's page on planet classification
• Gravity Rules: The Nature and Meaning of Planethood; S. Alan Stern; March 22, 2004
• On the status of Pluto; IAU, February 3, 1999