Is Pluto a Planet?

About this video

How to classify, or reclassify, celestial bodies.

With all the recent attention on Venus after its transit on 5/6 June, we thought we should focus on another planet, Pluto – but is it actually a planet?

Unfortunately for poor Pluto, we now know that it’s significantly less unique than we once thought it was. As C.G.P. Grey explains, Pluto actually exists with a number of similarly sized objects, far out in the Kuiper belt.

This problem with Pluto forms part of a much larger debate on the classification of the term 'planet'. Since the term was coined by the ancient Greeks, it has been continually revised to keep it in line with the development of our astronomical knowledge.

In 2006 the International Astronomical Union created an official classification of planets according to three essential criteria (view them here) – unfortunately, Pluto only meets two of these, relegating it to the position of ‘dwarf planet’.

Poor old Pluto.