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