Re: [GZG] No more pizzas!

["Eric Foley" <stiltman@xxxxxxxxxxxx>]

----- Original Message ----- 
From: <Beth.Fulton@xxxxxxxx>
To: <gzg-l@xxxxxxxxxxxxxxxxxxxxxxx>
Sent: Friday, August 25, 2006 12:57 AM
Subject: RE: [GZG] No more pizzas!


> G'day,

> > Actually, unless the press has grossly misquoted the wording of the
> > definition, Earth and Jupiter aren't planets either.  The plank of it 
> > that
> > demoted Pluto is, they have to "clear the neighborhood of space around 
> > their
> > orbit" to be a full planet.

> I'm still laughing over the fact any heavenly bodies outside our solar
> system can't be planets... they don't orbit the *sun* (as required by
> the new definition)...

I do think they actually have that one covered, because I think that this 
definition is for what is a planet inside our own solar system.  Presumably, 
the definition applies to what would make something a planet in other solar 
systems as well.

Upon further reading, evidently what they mean by "clearing the 
neighborhood" doesn't actually mean... well, "clearing the neighborhood", it 
just means that the object is of sufficient mass that all other objects that 
are of any significant size either have been pulled into orbit around it or 
flung away.  So evidently the fact that there are tens of thousands of 
asteroids camped at the L4 and L5 Lagrangian points of Jupiter and the Sun 
doesn't count, as none of these are large enough that they don't still 
consider it "clearing the neighborhood" of any other massive objects. 
Whereas Pluto (and for that matter, Ceres) are in belts of objects that are 
nearly as large as themselves and have not been either pulled into orbit 
around them nor flung out somewhere else.

It's still a cruddy definition that just phases the debate about what a 
planet is into a debate about what they really mean by "clearing the 
neighborhood" and how "clear" they really mean by "clear"... which is 
ultimately a debate about... well, what a "planet" is.  Thanks for nothing, 
IAU.

E 


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