Pluto is a unique planet located in the outer solar system. It was discovered in 1930 by American astronomer Clyde Tombaugh, making it the only planet discovered by an American. While Pluto has been known to exist for over 80 years, it remains difficult to study due to its great distance from Earth. Scientists have determined some properties of Pluto through observation, but its small size and distance have prevented close examination by spacecraft. Pluto continues to present mysteries for scientists to uncover.