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Annual observance

Pluto Discovery Day

February 18 Cultural / community observance Updated 2025-12-17

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Overview

Commemorating the discovery of Pluto by Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona, in 1930. This event expanded our understanding of the solar system, bringing to light the existence of the first Kuiper Belt object.

Observed each year on February 18, Pluto Discovery Day invites people to pause, share the story, and bring a little themed joy to their day.

Why it matters: Pluto Discovery Day on February 18 honors the groundbreaking achievement of Clyde Tombaugh, whose discovery of Pluto in 1930 broadened our understanding of the solar system and introduced the first known Kuiper Belt object. This day serves as a reminder of the importance of exploration and curiosity in advancing scientific knowledge.

Origin and story

Pluto was discovered by Clyde Tombaugh on February 18, 1930, when he was just 24 years old.

For 76 years, Pluto was classified as the ninth planet in our solar system before its reclassification as a dwarf planet in 2006.

Quick facts

  • DateFebruary 18
  • TypeCultural / community observance
  • Great forFriends, Families, Classrooms, Teams

Also on this date

Ways to observe

  • Learn how Pluto was discovered using photographic plates.
  • Explore what makes a dwarf planet.
  • Read about the New Horizons mission and its findings.
  • Learn how definitions in science evolve.
  • Appreciate how new technology expands knowledge.

Fun facts

  • Pluto's discovery was the result of a systematic search for a predicted "Planet X," even though it was later reclassified as a dwarf planet.

Sources and attribution

Pluto Discovery & Facts (NASA)

Pluto Overview (Encyclopaedia Britannica)

External links may lead to third-party websites.

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FAQ

When is Pluto Discovery Day?
It is observed on February 18 each year.
What is Pluto Discovery Day?
Commemorating the discovery of Pluto by Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona, in 1930. This event expanded our understanding of the solar system, bringing to light the existence of the first Kuiper Belt object.
How do people observe Pluto Discovery Day?
Learn about Pluto’s discovery and explore the science of dwarf planets.

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