The renowned American astronomer Percival Lowell deduced the existence of Pluto in the early 1900’s from his observations of the orbit of the planet Uranus. Lowell believed that irregularities in its orbit could only be accounted for by the existence of another undiscovered planet.
The discovery of Pluto by Clyde Tombaugh in 1930 proved Lowell right in the main. Another body was influencing the orbit of Uranus. But what kind of body was it?
Pluto was a different kind of planet. Its orbit was elliptical rather than circular. It was a rocky planet at the end of a line of gas giants rather than grouped with its rocky cousins in the inner solar system.
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