Pluto
In the 1840s, using Newtonian mechanics, Urbain Le Verrier predicted the planet Neptune existed. He discovered this after studying the orbit of Uranus. Neptune was seen later in the late 19th century. Astronomers then felt that another planet was disturbing Uranus's orbit. In 1906, Percival Lowell, a person from Boston began an extensive to search the ninth planet. He called it "Planet X". By 1909, Lowell and William H. Pickering had suggested many possible places in the Solar System where the planet could be. Lowell continued the research till 1916. However, it fetched no good result. On March 19, 1915, his observatory had captured two images of Pluto. Lowell did not know this. The pictures were not recognized then for what they were.