An International Astronomical Union (IAU) resolution in August 2006 changed the definition of a planet so that Pluto no longer qualified. The new definition placed Pluto in a new solar system category, "dwarf planets." However, the IAU definition remains controversial among astronomers.
Then, in June 2008, the IAU decided on a name for trans-Neptunian planets similar to Pluto—plutoid. This definition also remains problematic. Lowell Observatory, where astronomers discovered Pluto, still lists Pluto among the nine planets.
Defining a planet is also a cultural issue. An informal Internet poll running since 2006 gave a resounding YES to "Pluto is a Planet" by a 4.7 to 1 margin with over 27,400 votes counted by late August 2008. Changes in terminology do not affect the physical nature of Pluto or its place in history. Pluto will remain Pluto despite future controversy and discussion.
Howard L. Cohen