Pluto was discovered in 1930 by American astronomer Clyde Tombaugh. It was considered the ninth planet from the Sun. In 1992 however, this became a question after several other objects similar in size to Pluto were discovered beyond it's orbit in what's known as the Kuiper belt.

The International Astronomical Union, the internationally recognized authority for assigning designations to celestial bodies made the controversial call, and destroying Pluto as a planet.