• Question: why isnt pluto a real planet anymore? so what if its small? why does that matter?

    Asked by ava and hibba!! on 15 Jan 2025.
    • Photo: Sheridan Williams

      Sheridan Williams answered on 15 Jan 2025:

      Because if you include Pluto as a planet you’d have to include dozens of other objects of equal or smaller size. There are moons bigger than Pluto!

    • Photo: Kirsty Lindsay

      Kirsty Lindsay answered on 22 Jan 2025:

      Sometimes when we learn new stuff we end up reclassifying the old stuff to fit into the new classifications to make things easier to understand.

      Originally everyone was happy the solar system had nine plants, but then we found a lot of other small planet-type-thingies as telescopes got better, and some where bigger than Pluto!

      So, we could either have lots of lots of planets- big and small, with moons and without, possibility a bit lumpy, or we need a new way of dividing planet-types-thingies up.

      In 2006 lots of astronomers had a meeting and decided we needed new names for planet-type-thingies and a way of deciding for sure what a planet is. They decided planets have to be ball-shaped, go around a star and have enough gravity to clear their orbit.
      If a planet- type-thingy was a ball, and went round a star but is was too small to clear it’s orbit of little rocks then it could be a drawf planet

      Pluto was reclassified as a dwarf planet because it’s round (it has enough gravity to pull itself into a ball), it goes around a star ( the Sun) but it hasn’t totally cleared it’s orbit of other little rocks. We have a few dwarf planets like Sedna, Ceres, Makemake, Eris and loads more.

Comments

  • Photo: Andrew M

    Andrew M commented on :

    It’s part of the scientific process. Ideas are proposed, tested and accepted only until there’s newer and better information that suggests the original idea needs to be modified or junked.

    Pluto was a planet until new discoveries showed it to be different to the other 8 planets. The new definition isn’t a completely happy one – there are some problems with it so it won’t be a great surprise as we make further discoveries in the outer solar system and in the planetary systems of other stars if it changes again.

    It’s part of the joy of science – it flows, it flexes, it adapts and it evolves