Pluto Demoted Day
August 24 · Level 5 · #1161 of 2238
A playful anniversary of the day Pluto stopped being called a planet. On 24 August 2006, the International Astronomical Union voted in Prague on a definition of "planet", and Pluto became a dwarf planet.
How it is celebrated: space fans debate whether the demotion was fair, wear Pluto T-shirts, make sympathy cards and host themed quiz nights. A good party test is to see who can name all eight planets in order.
Pluto was discovered in 1930 by the American astronomer Clyde Tombaugh, and its name was suggested by Venetia Burney, an eleven-year-old schoolgirl from Oxford.