Why is Pluto no longer a planet?

The picture above was taken from the New Horizons spacecraft when it flew by at some point last year. In 2006 Pluto was demoted from a planet to a dwarf planet and here’s why.

To be a planet you have to fulfil certain criteria, they don’t just let anybody in! They have to:

  • Be large enough to form a spherical shape under the planets own gravity
  • Orbit the sun (cannot be a moon of another planet)
  • Have a clear orbital route (no other objects on the route)

The only one that Pluto does not satisfy is having a clear orbital route. The dwarf planet takes 248 earth years to orbit the sun so it won’t be clearing it anytime soon. Unfortunately you’re not a planet Pluto but you may re-apply for the position when you have cleared your orbit.

Although this is not included in the criteria to be classified as a planet, Pluto has an eccentric orbit on a different plane to the rest of the planets as below.

pluto-orbit-color

Pluto definitely stands out from the rest of the planets in this sense.

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