This Day in History: Pluto Is Discovered (Sunday, February 18th)

This Day in History: , Pluto Is Discovered.

February 18, 1930.

Once believed to be the ninth planet, Pluto was discovered at the Lowell Observatory in Flagstaff, AZ, by astronomer Clyde W.

Tombaugh.

Tombaugh discovered the tiny dwarf planet using a new astronomic technique of photographic plates combined with a blink microscope.

Pluto was given the Roman name for the god of the underworld in Greek mythology due to its surface temperature of -360° F.

Nearly four billion miles away from the sun, it takes Pluto approximately 248 years to complete one orbit.

.

Pluto's only known moon, Charon, has a diameter of a mere 737 miles.

In 2006, it was announced that Pluto would no longer be considered a planet because its orbit crosses into the orbit of planet Neptune.

While widely referred to as a dwarf planet, many argue that it should still be considered a planet.