Article discussing possible definitions that qualify objects, such as Pluto and Sedna in the Kuiper Belt, as being planets or not.

Discusses related discoveries and excerpts.

News release from NASA affirming Pluto's planetary status.

Looks at possible histories leading to its existence.

Clarification from the International Astronomical Union on Pluto's planetary status.

Articles discusses the debate whether Pluto should be included among the planets. [Atlantic Monthly]