Asked in Dwarf Planet Pluto
Pluto is not a planet any more?
July 05, 2011 12:40PM
The discovery of other similar objects to Pluto in more recent years has meant that astronomers either had to keep adding planets to the list, or we had to redefine what a planet actually was. In 2006, a new definition for a planet was established. It had to be approximately round, it had to orbit the sun and it had to have cleared its neighbourhood of all other objects - so that at that distance from the sun, there were no other sizable bodies. Pluto is not large enough to have done the latter, while all other remaining planets have, so it was downgraded to a dwarf planet. There are now eight planets recognised and five Dawrf planets, of which Pluto is one.