In 1930, astronomer Clyde Tombaugh discovered the fabled “Ninth Planet” (or “Planet X”) while working at the Lowell Observatory in Flagstaff, Arizona. The existence of this body had been predicted previously based on perturbations in the orbit of Uranus and Neptune. After receiving more than 1,000 suggestions from around the world, and a debate among the Observatory’s staff, this newfound object was named Pluto—which was proposed by a young schoolgirl from Oxford (Venetia Burney).
Click here for original story, Pluto’s orbit is surprisingly unstable
Source: Phys.org