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Dwarf Planets

Right now, there are three requirements that must be met to be considered a planet.

  1. Orbits the host star of its solar system
  2. Has a mostly round shape
  3. Is big enough that it's cleared the nearby area of other debris

For a while, it was just those first two, but they added the third one in 2006. See, around that time, they found a bunch of new things that would've been considered planets. People argued that we couldn't have so many planets in our solar system, so we'd have to change the definition. Somehow, that third criteria gets all of the planets that are too small without just adding a size requirement. Even with this criteria, there's still a lot of dwarf planets. Dwarf planets can also be classified as minor planets.

Pluto

  • Was once considered the 9th planet in our solar system
  • Year is 247.94 Earth years
  • Day is 6.387 Earth days
  • Name proposed by Venetia Burney, who was 11 at the time

Ceres

  • Was considered a planet in the 1800s
  • Located between Mars and Jupiter
  • Year is 466.6 Earth days
  • Day is 9 hours and 4 minutes
  • Named after the Roman goddess of corn and harvests