Planet (alternative definition)

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See also planet (astronomy), Planet (Stern and Levison's definition).

At the meeting of the International Astronomical Union at which the official definition of a planet was adopted, a sizable minority voted for an alternative definition. This would have used the term "classical planet" for the eight covered by the definition actually adopted. The term "planet" would have covered both classical planets and dwarf planets. In brief, a planet would have been a round body orbiting the sun. This definition is supported by some astronomers.[1]

By this definition there would currently be 13 confirmed planets, listed here in order outward from the sun (more precisely, half way between the minimum and maximum distances):

  1. Mercury
  2. Venus
  3. Earth
  4. Mars
  5. Ceres
  6. Jupiter
  7. Saturn
  8. Uranus
  9. Neptune
  10. Pluto
  11. Haumea
  12. Makemake
  13. Eris

In the original proposal by the committee appointed by the IAU to draw up a definition, Charon would have been added as a twin planet of Pluto, making 14 planets in all.


  1. Boyle, The Case for Pluto, Wiley, 2010; Jones, Pluto, Cambridge University Press, 2010, pages 180f