[ExI] new ninth?

[John Clark]

On Sun, Jan 24, 2016 at 7:41 AM, Anders Sandberg <anders at aleph.se> wrote:

>
> http://www.sciencemag.org/news/2016/01/feature-astronomers-say-neptune-sized-planet-lurks-unseen-solar-system
>
> ​> ​
> Would it actually count as a planet? I seem to recall that the
> Pluto-killing definition includes "has cleared its orbit of planetesimals".
>

​I've never quite understood ​that definition. Neptune hasn't cleared its
orbit of Pluto so why is Neptune a planet?

  John K Clark
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