In 1930, 24-year-old astronomer Clyde Tombaugh discovered Pluto beyond Neptune. It was counted as the Solar System’s ninth planet for 76 years. It was named Pluto, and for decades, it proudly held the title of ninth planet.
But not everyone was convinced.
Pluto was weird:- It is small: about one-sixth the Moon’s mass.
- Its orbit is tilted and more elongated than the major planets’.
- Its orbit crosses Neptune’s distance from the Sun, though the two bodies do not collide.
🪐 The Planetary Breakup Came in 2006
At its 2006 General Assembly, the International Astronomical Union (IAU) adopted a Solar System definition. A planet must:
- Orbit the Sun ✅
- Have enough gravity to become nearly round ✅
- Clear the neighborhood around its orbit ❌
Pluto shares its orbital zone with many objects in the Kuiper Belt, so it does not meet the third criterion. The IAU classifies it as a dwarf planet, a separate category under that definition. IAU’s 2006 resolution
💔 Public Reaction? Outrage.
Schoolchildren protested.
“Plutoed” became slang for being unfairly demoted.
Even Neil deGrasse Tyson got hate mail for supporting the change.
But here’s the twist: Pluto didn’t shrink. Our definition of a planet evolved — just like science should.
So while Pluto may have lost its planetary passport, it gained something rarer: legend status.