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Old February 13 2013, 11:57 PM   #58
RJDiogenes
Idealistic Cynic and Canon Champion
 
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Re: Help name the moons of Pluto

Rhubarbodendron wrote: View Post
How about counting anything as a planet that revolts directly around a sun plus has an atmosphere or used to have one?
With this definition we could keep all the original planets*, exclude big asteroids and include the more interesting objects yet to be found.
But that's my point-- the definition shouldn't be designed to exclude or include specific objects. The definition should be made based on certain criteria, just as in the categorization of stars or species, and then stuff will either fit the definition or not. In my opinion, a planet should be an object that is large enough to reach hydrostatic equilibrium and orbits a star.

Only Jupiter's moon Europa would cause difficulties as it does indeed have traces of an atmosphere. It's a matter of definition if we consider Europa/Jupiter to be a binary planet (after all there are binary suns) or if we exclude Europa, based on the fact that it's not immediately circling the sun.
Titan has a dense atmosphere, and other moons have atmospheres to various degrees. But that doesn't matter. If it orbits a planet, it's a moon. If something the size of Neptune was orbiting Jupiter, it would still be a moon.

Alidar Jarok wrote: View Post
Shouldn't they be Erisian objects? I'm confused at why you aren't arguing more for Eris than Pluto, since it's a more massive dwarf planet.
There are several terms bandied about. It doesn't really matter which one you prefer. The point is that the definition of planet is arbitrary and inconsistent, and was made for political rather than scientific reasons.
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