Planets vs Asteroids
There’s an urban legend going around since 2006 that says “asteroids used to be planets, but astronomers discovered they exist in a belt so way back in the mid 1800s the astronomers reclassified them as non-planets. For the same reason, Kuiper Belt objects like Pluto should be non-planets because they, too, are in a belt.” I call this an urban legend because that’s all it is. There is no truth behind the claim that asteroids were made non-planets because they exist in a belt. The evidence makes this overwhelmingly clear. If you don’t believe me, then for now read this one quote from the International Astronomical Union (IAU) resolutions as recently as 1948:
In the case of a planet that passes closer to the Earth than the orbit of Mars, a definitive number can be given after a single opposition, provided that the planet has been well observed, and that a satisfactory orbit has been obtained. (translated from French; bold added)
Yep, they were considered a type of planet, so calling them planet was perfectly legitimate, all the way into the 1950s, even though everybody knew they are in a belt and don’t clear their orbits. The ...