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May 24, 1930

In 1930, Pluto was announced to be the name chosen for the newly-discovered ninth planet (previously known as Planet X) by Roger Lowell Putnam, trustee of Lowell Observatory, Flagstaff, Arizona, (and nephew of the late Percival Lowell who had established the observatory and initiated the search there for the ninth planet). Pluto was located on 13 Mar 1930 by Clyde Tombaugh at that institution. Putnam was quoted on the front page of the New York Times, saying, “We felt in making our choice of a name for Planet X, that the line of Roman gods for whom the other planets are named should not be broken, and we believe that Dr. Lowell, whose researches led directly to its discovery, would have felt the same way.” Pluto in mythology was the ruler of the underworld, regions of darkness. “P.L.” is also Lowell's monogram.