Re: "Pluto Now Called a Plutoid"

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).

Eris is not a planet either as it is not much more massive than the potentially colliding mass in its region of space. Ceres is about one third the mass of the potentially colliding mass, Eris is about one tenth the mass of the potentially colliding mass, and Pluto is about one thirteenth the mass of the potentially colliding mass

The definition might seem a little fuzzy but nothing lies remotely close to the boundary so it is absolutely unambiguous in practice. Ceres, the most planet like dwarf planet is about one third of the mass of the potentially colliding bodies, Neptune the least planet like of all the Planets is 24 thousand times as massive as the potentially colliding mass. The gap is about four orders of magnitude.

If the Kuiper wall is created by an object, this object will have cleared its orbit and will therefore be a planet. It might lie closer to the boundary than any of the currently known objects.
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