© Wikipedia Commons; nagualdesign; Tom Ruen
Pluto used to be thought of as the ninth planet in the Solar System, but in 2006 the International Astronomical Union created an official definition for planets and decided Pluto didn’t fit all of the conditions. The upshot was a reclassification of the body discovered by Clyde Tombaugh at Lowell Observatory in 1930, with Pluto being labelled a ‘dwarf planet’ instead. But that’s not to say a ninth planet doesn’t actually exist. In fact, as time goes on, there’s more and more evidence to suggest one is very much out there.
The search for a ninth planet has been ongoing for some time. American astronomer Percival Lowell spent the last decade of his life looking for a hypothetical planet beyond Neptune – the so-called Planet X. It was thought that another planet in the outer reaches of the Solar System would account for the apparent irregularities in the orbits of Uranus and Neptune, and when Pluto was discovered it seemed the search was over.