Charon and Pluto are getting classified as twin planets. Charon is about 50% the size of Pluto and 12% the mass. Earth's moon is only 20% the size of earth and 1% the mass. I've yet to read what the proposed divide between moon and twin planet is, but there is a significant difference between the relative size of Earth and its moon, and Pluto and Charon.
I did a bit more searching and found an article on wiki under "double planet (http://en.wikipedia.org/wiki/Double_planet)". It says the term is "informal" but the common definition is based upon the center of orbit. The Earth and the Moon, and Pluto and Charon are apparently the only examples of the traditional planets where the relative masses and sizes were close enough to need a more specific definition.
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timeasmymeasure
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Date: 2006-08-16 02:00 pm (UTC)1. Charon? WTF? It orbits PLUTO, not the sun directly. Doesn't that mean that Titan et all will also qualify as planets?
2. They really really really need to find a better name than "Xena."
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Date: 2006-08-16 02:07 pm (UTC)Does Charon and Pluto's common orbit point fall inside of Pluto or are both bodies actually in orbit around one another?
Binary planets in the same solar plane.
-PT
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Date: 2006-08-16 05:19 pm (UTC)no subject
Date: 2006-08-16 05:55 pm (UTC)no subject
Date: 2006-08-16 06:07 pm (UTC)no subject
Date: 2006-08-16 02:42 pm (UTC)now what will they say?
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Date: 2006-08-16 02:48 pm (UTC)no subject
Date: 2006-08-17 12:04 am (UTC)