Discovery of Pluto
Due to Pluto's immense distance from Earth, it was not discovered until 1930. Furthermore, its discovery was a serendipity, credited toward a fortunate accident. The curiosity for a planet beyond Neptune began with a man named Percival Lowell, who believed that there exists a "Planet X" somewhere in the outer reaches of our solar system, based on calculations done with the study of the motions of Uranus and Neptune. Lowell funded three searches for the Planet X and set up the Lowell Observatory in Flagstaff, Arizona. The first two searches turned up nothing, but efforts continued. On the third search, Dr. Vesto Slipher, the observatory director hired a young 24-year-old man from Kansas named Clyde Tombaugh to assist in the endeavor. Tombaugh conducted a survey of the sky by taking sets of photographs, each one to two weeks apart. Any shifting of any object against the backdrop of the stars indicated the presence of a planetary body. Through this repeated procedure, the planet Pluto was found on February 18, 1930.
Pluto was officially named and labeled as the ninth planet by the International Astronomical Union in 1930. Its name was based on the Roman go of the underworld, Hades and also rumored to be the initials of the man who carved the path to discovery: Percival Lowell (P.L.uto).
However, even with this discovery, calculations indicated that Pluto was still too small to be the Planet X that Lowell had been searching for. Its size was too small to affect the orbit of Neptune as predicted. Thus the search went on. However, this effort was proved to be in vain because the data used in the calculations turned out to be erroneous and was resolved when data from the Voyager 2 was used. Therefore, there is no tenth planet and Pluto is the last planet in our solar system to be discovered.