Pluto's status as a planet

Cause of death

Killed by regulation

Made by

International Astronomical Union

424 astronomers in Prague voted to define "planet" in a way that excluded it.

Pluto was a planet for 76 years on the strength of having been found. The IAU's 2006 vote required a planet to orbit the Sun, be round, and have cleared its orbital neighbourhood; Pluto manages the first two. The decision was made by a fraction of the IAU's membership present on the final day of the General Assembly, which is part of why the public never fully accepted it and why the argument is still live twenty years later.