chapter  13
WithPatrick Moore
Pages 7

Pluto, the outermost known planet of the Solar System, was discovered in 1930 by Clyde Tombaugh, from the Lowell Observatory at Flagstaff in Arizona. It is the only planet not yet encountered by a space probe, and as a result our knowledge of it is very far from complete. It is accompanied by a smaller body, Charon, whose diameter is more than half that of Pluto itself.