Re: "Pluto Now Called a Plutoid"

Brett Paul Dunbar wrote:

In message <4b025605-faeb-465b-ab4f-70647fb2e05e@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, Quadibloc <jsavard@xxxxxxxxx> writes

As for Pluto, however, since it _is_ much larger than any other
Plutino, it _has_ cleared its own orbit of everything but debris, even
if there are similar bodies in orbits only a little further out, so it
could be left as a planet (but then its diameter, rather than
Mercury's, would mark the dividing line between a QPC and a PC). That
would also mean that Eris would become a planet after we knew that it
was significantly bigger than all the Erisinos out there...

Pluto isn't a planet because it hasn't cleared its orbit Neptune has. Neptune has cleared that region of space of debris, what's left either orbits Neptune (e.g. Triton the second largest object in that region), is in a resonance with Neptune (e.g. Pluto, the third largest object) or is a transient (e.g. various Comets).

More accurately and succinctly: Pluto is no longer a planet because the IAU said so. Their "objective" definition was so vague that they had to include a list of planets to make sure people knew what modifications that entailed, and Pluto wasn't on it.

--
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Relevant Pages

  • Re: "Pluto Now Called a Plutoid"
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    (rec.arts.sf.science)
  • Re: "Pluto Now Called a Plutoid"
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    (rec.arts.sf.science)
  • Re: "Pluto Now Called a Plutoid"
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    (rec.arts.sf.science)
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