An international committee of astronomers agreed Pluto wasn't really a planet in 2006. They reclassified it as a 'dwarf planet' instead. The decision was made after Mike Brown of the California Institute of Technology identified a larger body, Eris, in the Kuiper Belt. He has been telling Bethan Head about his discovery and the public outcry that followed.

Photo: Dwarf planet Pluto Credit: DottedHippo /Getty Images