Sites discussing whether Pluto should be properly considered a planet, a Kuiper Belt object, or some other form of Trans-Neptunian Object (TNO).

In 1999 the International Astronomical Union announced that it was premature to consider removing the "planet" label from Pluto, but as more TNOs are discovered, the debate may be re-opened. For example, a TNO larger than Pluto, 2003 UB313, was announced in 2005.