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The Discovery of Pluto

IN SHORT - Pluto was found in 1930 only. The search for an hypothetical "Planet X" had been initiated by the famed US astronomer Percival Lowell, in Flagstaff, Arizona, as it eventually was an amateur astronomer, Clyde W. Tombaugh -who had been hired first to take photographs at the

observatory and who then came to blink the pictures- who eventually, through a systematical search at the moment of the opposition of the planet, found the faraway world. Pluto had alreday been imaged on plates taken in 1915 and 1929, as it had then gone unseen

Pluto was discovered on February 18th, 1930 at the Lowell Observatory. The Lowell Observatory at Mars Hill, Flagstaff, Arizona, had been founded in 1894 by Percival Lowell (1855-1916). Percival Lowell was from a well known family of Boston and he eventually decided to be an astronomer. He built the observatory in the purpose of searching for intelligent life at Mars. It's there, with a 24-inch Clark telescope, that Lowell thought he saw the famed "Mars canals". On the other hand, during the last 13 years of his life, Lowell turned most of his energy to the quest of "Planet X", an hypothetical 9th planet beyond Neptune. After his death in 1916, and a length of time due to will litigation, the quest was taken back by Powell's heirs with a 13-inch telescope. Clyde W. Tombaugh, an enthusiastic amateur astronomer was hired by the Lowell Observatory in 1928 to participate to continuing the quest for "Planet X"!. Clyde W. Tombaugh (1906-1997) had sent sketches of Jupiter and Mars he had made in western Kansas through a quality home-made 9", f/9 reflector to the astronomers of the Lowell Observatory for comments and suggestions. Tombaugh was first in charge of taking the photographs as plates were scanned by others. Pluto failed to be on the plates

As the astronomers at Lowell Observatory could not devote further time to blinking due to their other work, Tombaugh, in June 1929, became in charge of both photographying and blinking. Furthermore, he changed the method and systematically looked where the predictions said that Pluto ought to be at its opposition, that is in the best possible conditions of luminosity and visibility. Eventually, using three plates taken in January 21st, 23rd, and 29th, 1930, Tombaugh discovered Pluto at 4:00 p.m. Moutain Time on February 18th, 1930! The name given to the new planet was eventually "Pluto", from the Greek god of the underworld, a perfect naming for a planet dwelling in the dark outreaches of the solar system. Its symbol is "PL" which are the two initials letters of Pluto as well as the monogram of Percival Lowell. Curiously, Pluto already was on two plates taken by Lowell in March and April 1915 as it was on a pair taken in the beginning of 1929 when the search was taken back. The Tombaugh discovery was officially announced on March 13th, 1930 by the Lowell Observatory. Later dismissed from Lowell in 1945, Tombaugh eventually worked at White Sands Proving Grounds, developing the optical tracking telescopes used for the fledgling U.S. space program, as he teached 1957-1973 at the New Mexico State University

Pluto is the least known planet of the solar system. It's the object of the NASA's mission New Horizons, which will reach the ultimate planet of the solar system in July 2015. The mission will provide the first surface high-resolution images ever of Pluto and its moon Charon. The probe will then continue its journey to visit one or more Kuiper Belt objects, these icy bodies left behind when the solar system formed. Pluto was dismissed in 2006 of its status of planet by the International Astronomical Union (IAU) which re-organized its categories of the celestial bodies inside a solar system. for more, see our tutorial "Solar System Planets"