Discovery, Demotion and New Horizons

Discovered in 1930, Pluto became the ninth planet in our Solar System – a distinction it would hold for at least 6 decades.  In the 1990’s, the ongoing discovery of objects beyond the orbit of Neptune cast doubts on Pluto’s status and in 2006 the International Astronomical Union’s adoption of a formal definition of a planet effectively demoted Pluto.  This was controversial, as Pluto was (and remains) a favourite ‘planet’ for a lot of people, particularly children.

Pluto would remain a mysterious world, due to its small size and immense distance from Earth – even the Hubble Space Telescope could not resolve details on its surface.  This would change dramatically in 2015 when the New Horizons spacecraft sent back stunning images, answering many questions about Pluto’s composition, atmosphere and surface features.