• Question: Do dwarf planets exist?

    Asked by to Sam, Roberto on 23 Jun 2014. This question was also asked by .
    • Photo: Sam Connolly

      Sam Connolly answered on 23 Jun 2014:

      Yes, Pluto is one! Originally it was classified as a planet, but not long ago Astronomers started to find a lot of objects which are a similar size to Pluto, then eventually one which was bigger, called Eris. Rather than keep adding loads of planets (there are probably hundreds of dwarf planets in the solar system), they reclassified Pluto as a dwarf planet, along with Eris. Most of them are in something called the Kuiper belt, which is an area full of rocks and comets beyond Neptune, but there are a few in the Asteroid belt, like Ceres. The difference between a dwarf planet and an asteroid or comet is that they’re big enough that their gravity can hold them together.

    • Photo: Roberto Trotta

      Roberto Trotta answered on 24 Jun 2014:

      Yes, now they do! They were invented in 2006 because Pluto, the most distant and smallest planet in the solar system, was really too small to be called a planet.

      Pluto is smaller than our Moon, so it seemed unfair that it should be called a planet. So astronomers decided to call it a dwarf planet, and created this new category of objects. It is possible that there are more such objects, even further out than Pluto. But they are very difficult to spot.

      Some people say that another small object (76 times further away from the Sun than the Earth) called Sedna should also be a dwarf planet. But nobody has actually made a decision on that yet.

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