My 2 cents on the
Pluto planet/planetoid debate:
There is one
commonality shared by Mercury, Venus, Earth, Mars,
Jupiter,
Saturn, Uranus and Neptune
-- and NO other known solar system bodies.
They
each represent more than 50% of the
total mass of all other bodies
in a
similar
orbit. Note that Ceres
would not be part of this group -- it
is
not
more
massive than the sum of all
other asteroids in a similar
orbit.
Pluto,
likewise, would not meet this
requirement -- like Ceres, it is
the
largest body in its
type of orbit, but the sum of the masses of all
other
bodies
in similar orbits exceeds that of
Pluto.
The nice thing about this
definition is that it is simple and
unambiguous.
--Rob
