AssetID: 53475175
Headline: This Day in History: Pluto Is Discovered
Caption: Once believed to be the ninth planet, Pluto was discovered at the Lowell Observatory in Flagstaff, AZ, by astronomer Clyde W. Tombaugh.
Keywords: This Day in History,Pluto discovery,February 18,1930,Lowell Observatory,Flagstaff,AZ,Clyde W. Tombaugh,ninth planet,astronomical discovery,photographic plates,blink microscope,dwarf planet,Roman god of the underworld,Greek mythology,surface temperature,orbit,Charon,moon,solar system,reclassification,Neptune,planet debate
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