The discovery of Pluto was the culmination of a systematic search for a new planet beyond Neptune, initiated by the American astronomer Percival Lowell. In the late 19th and early 20th centuries, Lowell theorized the existence of a planet due to perceived perturbations in the orbits of Neptune and Uranus. After Lowell's death in 1916, his observatory continued the search, eventually leading to Clyde Tombaugh's work beginning in 1929. Using a method called 'plate comparison,' Tombaugh meticulously compared photographic plates to spot the moving celestial body against the fixed stars. On February 18, 1930, Tombaugh confirmed the presence of a new object, which he initially designated as 'Planet X'. The formal announcement took place on March 13, 1930, at Lowell Observatory in Flagstaff, Arizona.

This revelation captured the imagination of the public and the scientific community alike. Tombaugh's discovery was received with great excitement, as it represented not just a finding of a new celestial body but also validated the ongoing quest for understanding the cosmos. The official naming of Pluto took place later in the same year, and despite its small size, it was designated as the ninth planet of our solar system, fitting well into a growing field of astronomy focused on distant planetary bodies.