Astronomy Question of the Week: Why is Pluto no longer a planet?

It happened on 24 August 2006: instead of the nine planets it had up to that time, our Solar System suddenly had only eight ? the planet Pluto was no longer a planet. What happened?
In August 2006, astronomers from all over the world gathered at the 26th General Assembly of the International Astronomical Union (IAU) [...]

Full story at http://spacefellowship.com/2009/10/05/astronomy-question-of-the-week-why-is-pluto-no-longer-a-planet/