Pluto was demoted from planetary

In order to put these matters to rest, in August 2006, 3,000 astronomers and scientists of the International Astronomical Union (IAU) gathered in Prague, Czech Republic to deliberate. The organization planned to publish an official definition of "planet", ruling on whether to call Pluto a planet, dwarf planet or a Kuiper Belt Object (KBO).[24][25] The draft proposal classified Pluto along with 2003 UB313 and any other spherical TNOs that may be discovered, as planets, although they would have been informally labelled 'plutons'. The asteroid 1 Ceres and Pluto's moon, Charon, would also have been considered planets.

On August 24, 2006, however, the previous draft was reversed, according to the newly passed rule, Pluto was demoted from planetary status to a dwarf planet and is accompanied by Ceres and 2003 UB313 in this category. There are three main conditions for an object to be called a 'planet', according to the IAU resolution.

1. The object must be in orbit around a star, but not be a star itself.
2. The object must be massive enough to be a sphere by its own gravitational force.
3. It must have cleared the neighborhood around its orbit.