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Pluto’s celestial body, already considered the Solar System planet farthest from the Sun, the International Astronomical Union demoted to dwarf planet in 2006. The orbit of Pluto, highly elliptical, has a semi-major axis of 5.9 billion kilometers. Equally at Venus, Pluto rotates on itself in a retrograde direction (ie in the opposite direction to that of its motion of revolution around the Sun). In other words, the axis of rotation of Pluto is inverted with respect to that of the Earth: the north pole lies below the orbit plane and the south pole above. The period of rotation is of 6.39 days. The equator is tilted 58 degrees to the orbital plane. The diameter measuring ~2300 km (less than 1/5 of that of the Earth). The existence of a planet beyond Neptune was hypothesized, between 1915 and 1920, by W.H. Pickering and P. Lowell, to explain some perturbations of the orbits of Uranus and Neptune. The research of the planet were, at first, in vain. Only in 1930, the Observatory in Flagstaff (Arizona), C. Tombaugh discovered Pluto a few degrees away from the intended position by Pickering and Lowell calculations. In January 2006, NASA launched the New Horizons spacecraft to Pluto at a time. The encounter with the planet took place July 14, 2015: Five Paths billion kilometers, to 13,49 ’57 “probe at a speed of 13.78 kilometers per second, it is passed to a minimum of 12,500 km above the surface distance the dwarf planet to take close-up images of its surface. In 1978, J. W. Christy discovered the first satellite, Charon, opening new horizons in the search. First, the period of revolution and the size of the orbit of the satellite, and applying the third law of Kepler, he could calculate the mass of Pluto, but he himself was far less massive than hitherto had been thought.