• Question: how many planets are in the solar system?

    Asked by chloelouise to Sheila, Rob, Geoff, Adam on 15 Mar 2011 in Categories: .
    • Photo: Geoff McBride

      Geoff McBride answered on 14 Mar 2011:

      8, or 16. If you include Pluto then you should include the others past Pluto [I think it’s 16] lumps of ice most of them. But how about Io, Europa, or Titan couldn’t they be planets in some sense.

    • Photo: Sheila Kanani

      Sheila Kanani answered on 14 Mar 2011:

      Eight!
      Plus lots of dwarf planets, planetessimals, asteroids, comets and junk 🙂
      I love Pluto though, I love anything that is small (I’m a bit biased towards small things).
      If you live in Illinois you might think that Pluto is still a planet:
      http://www.guardian.co.uk/science/blog/2009/mar/06/is-pluto-a-planet
      I don’t think it really matters what labels we give things though, we’ll still treat Pluto the same way as before. No one likes to be labelled 🙂

    • Photo: Adam Tuff

      Adam Tuff answered on 14 Mar 2011:

      This depends on what people class as a planet – the science community recently decided that a planet is something that has “cleared the neighbourhood” – this means that the planet is the only massive object in it’s orbit. Pluto hasn’t cleared it’s orbit as there are lots of large asteroids orbiting near by, and Charon, Pluto’s moon, is actually pretty big compared to it (there are also a whole list of other reasons too). So, using the current classification system, there are 8 planets.

    • Photo: Robert Simpson

      Robert Simpson answered on 15 Mar 2011:

      There are now eight planets an a handful of dwarf planets (smaller objects that aren’t quite fully-fledge planets). Pluto was ‘demoted’ a few years ago to be a dwarf planet after a larger body was found, called Eris.

      There is also a dwarf planet in the asteroid belt, called Ceres. Dwarf planets are objects which are big and round, that orbit a star and that have mostly cleared their orbits of other bodies. Pluto seems to share its orbit with a whole bunch of other asteroid-like objects and this is one of the reasons the dwarf planet category was created.

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