On February 18, 1930, astronomer Clyde Tombaugh at the Lowell Observatory in Arizona identified a new celestial body while comparing photographic plates of the night sky. The discovery would later be named Pluto, becoming the ninth known planet of the solar system for much of the twentieth century.
Tombaugh located the object using a blink comparator, a mechanical device that allowed astronomers to detect movement between photographs taken days apart. The images revealed a faint point of light shifting position against a static field of stars, confirming the presence of a previously unknown world beyond Neptune.
The search for what was then called “Planet X” began years earlier under astronomer Percival Lowell, whose calculations suggested another planet might exist at the outer edge of the solar system. Although Lowell did not live to see the discovery, the observatory bearing his name ultimately completed the work.
Following confirmation, the object was officially announced later in 1930 and named Pluto after the Roman god of the underworld, reflecting its distant and dark orbit. For decades, Pluto remained classified as a planet until the International Astronomical Union redefined planetary criteria in 2006, reclassifying it as a dwarf planet.
Despite that change, the discovery remains one of the most significant milestones in observational astronomy. It demonstrated the power of systematic sky surveys and helped shape modern planetary science, influencing future missions and the continued exploration of the Kuiper Belt.
About the Author Brad Socha is the founder of The Universal Record, focused on sourced, factual global reporting. Coverage includes international news, geopolitics, technology, and major developments.
