This Day in History: <br />Pluto Is Discovered February 18, 1930 Once believed to be the ninth planet, <br />Pluto was discovered at the Lowell <br />Observatory in Flagstaff, AZ, by <br />astronomer Clyde W. Tombaugh. Tombaugh discovered the tiny, dwarf <br />planet using a new astronomic <br />technique of photographic plates <br />combined with a blink microscope. Pluto was given the Roman name <br />for the god of the underworld in <br />Greek mythology, due to its <br />surface temperature of -360° F. Nearly four billion miles away <br />from the sun, it takes Pluto <br />approximately 248 years <br />to complete one orbit. Pluto's only known moon, <br />Charon, has a diameter <br />of a mere 737 miles. In 2006, it was announced that Pluto <br />would no longer be considered a <br />planet due to the fact that its orbit <br />crosses into the orbit of planet Neptune.
