Re: Toward a Rational Definition of what is a Planet

In article <q7thj15epq07jtieo43me5shat478aflol@xxxxxxx>,
Daggaz <answer.in.this@newsgroup> wrote:
>How about we forget about trying to keep Pluto as a planet. Pluto has
>significantly lower mass than at least 6 of the solar systems moons and is
>part of a large population of bodies (the Kuiper Belt) that includes objects
>of similar size to Pluto.
>
>Setting the lower limit of a planet to Pluto's size would put Pluto, UB313
>and who knows how many other objects to a higher status than many moons.
>This wouldn't be wrong if it wasn't so arbitrary. Setting the lower limit
>the minimum mass for sphericity would be impractical because it would
>include too many objects.
>
>Therefore I think the mass of the solar system's largest and most massive
>moon, Ganymede, (but not its size, that would exclude Mercury) should be set
>as the lower limit for the mass of a planet. Anything smaller but still
>spherical is a planetoid.

I read a not in my newspaper yesterday that the IAU has taken a radical
approach on this question: their latest suggestion is to get rid of the
term "planet" altogether, and to replace it with more specific terms, such
as "terrestial planet", "gas giant", "Kuiper belt object", "exoplanet".

Of course people will continue to use the word "planet" anyway, but the
IAU will not give any official definition of the word "planet" but
recommends not using it but replacing it with a more specific term which
is appropriate.

There's at least one advantage with this latest suggestion from the IAU:
there are no border cases. There's no disagreement about whether some
particular planet is a "terrestial planet", "gas giant", "KBO" or "exoplanet".



>On 26 Sep 2005 21:42:56 -0700, edward12@xxxxxxxxxxx wrote:
>
>|Why not just say that anything smaller than Pluto is just a "Minor
>|Planet" and anything Pluto's size or larger is a Planet?


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