On This Day, February 18, 1930, Pluto, once believed to be the ninth planet in our solar system, was discovered at the Lowell Observatory in Flagstaff, Arizona, by astronomer Clyde W. Tombaugh. This discovery was a significant achievement in the field of astronomy, adding a new member to the family of known planets in our solar system at the time.
Tombaugh’s discovery was the result of systematic searches for a ninth planet, often referred to as “Planet X,” theorized to exist beyond Neptune due to unexplained perturbations in the orbits of Neptune and Uranus. Using a technique that involved comparing photographic plates taken weeks apart to detect moving objects, Tombaugh identified Pluto. This method allowed for the detection of changes in position against the relatively fixed background stars.
Pluto’s discovery was a momentous occasion that captured the public’s imagination and expanded our understanding of the solar system. However, the understanding of Pluto’s status has evolved; in 2006, the International Astronomical Union reclassified Pluto as a “dwarf planet” due to its size and the discovery of similar-sized objects in the Kuiper Belt. Despite this, Pluto’s discovery remains a landmark event in the exploration of our solar system, illustrating the ongoing quest for knowledge and understanding of the cosmos.
