Pluto was discovered on February 18, 1930, by American astronomer Clyde W. Tombaugh at Lowell Observatory in Flagstaff, Arizona.

Quick Scoop

  • Discovery date: February 18, 1930.
  • Discovered by: Clyde W. Tombaugh, a young astronomer working at Lowell Observatory, who was hired specifically to search for a predicted “Planet X.”
  • How it was found: Tombaugh compared photographic plates of the same patch of sky taken on different nights and noticed a tiny point of light that had shifted position, revealing Pluto’s motion against the background stars.
  • Public announcement: The discovery was announced on March 13, 1930, quickly becoming a worldwide news story and adding a “ninth planet” to school textbooks for decades.

In short, if you’re wondering “when was Pluto discovered?” the key date to remember is February 18, 1930.

TL;DR: Pluto was discovered on February 18, 1930, by Clyde W. Tombaugh at Lowell Observatory, and the find was announced to the world a few weeks later on March 13, 1930.

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