• Question: Do you class Pluto as a planet because some people don't?

    Asked by anon-219943 to Nicolas, Emma, Declan, Bella on 20 Jun 2019.
    • Photo: Bella Boulderstone

      Bella Boulderstone answered on 20 Jun 2019:

      The major astronomy groups have classified Pluto as a dwarf planet rather than a planet. So it’s not a planet anymore. It’s in a group with Haumea, Makemake, Eris and Sedna. It was actually the discovery of Eris (2005) that made the International Astronomical Union have to put down some clear boundaries onto what was and was not a planet, before then there weren’t clear rules!
      So here they are (for our Solar System):
      1. Have to be in orbit around the Sun (looking good for Pluto so far)
      2. Has to have pulled itself into a sphere (otherwise a whole bunch of comets would be in, and there are thousands of them, but a tick for Pluto here).
      3. Have cleared its neighbourhood (ah)
      Pluto hasn’t actually cleared the area around its orbit, so unfortunately it’s not a planet, it’s a dwarf planet. Otherwise we’d have to learn that there were many more planets instead of just nine! We’d be on at least 13!

    • Photo: Declan Jonckers

      Declan Jonckers answered on 20 Jun 2019:

      As Bella mentioned, technically Pluto isn’t a planet according to the International Astronomical Union (IAU). But it’s a dwarf planet, which sounds like a kind of planet to me!

      In reality, there’s lots of problems with large organisations determining what words mean, technically planets in other solar systems aren’t planets! Which all seems a bit strange.

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