On 12/04/2012 2:13 PM, Wayne Throop wrote:
> : oriel36<
kellehe...@gmail.com>
> : Of course the orbit of Pluto temporarily changes place with Neptune so
> : Neptune hasn't cleared its orbit of smaller objects so I guess Neptune
> : is disqualified as a planet.
>
> Interesting guess. Do you think you're right and nobody at the IAU
> has caught this glarring error? Maybe you should tell them.
>
Definitely not an error. It's a matter of defining the interpretation:
Stern, currently leading the NASA New Horizons mission to Pluto,
disagrees with the reclassification of Pluto on the basis that—like
Pluto—Earth, Mars, Jupiter and Neptune have not cleared their orbital
neighbourhoods either. Earth co-orbits with 10,000 near-Earth asteroids
(NEAs), and Jupiter has 100,000 Trojan asteroids in its orbital path.
"If Neptune had cleared its zone, Pluto wouldn't be there," he now says.[5]
However, in 2000 Stern himself wrote, "we define an überplanet as a
planetary body in orbit about a star that is dynamically important
enough to have cleared its neighboring planetesimals ..." and a few
paragraphs later, "From a dynamical standpoint, our solar system clearly
contains 8 überplanets"—including Earth, Mars, Jupiter, and Neptune.[2]
Most planetary scientists understand "clearing the neighborhood" to
refer to an object being the dominant mass in its vicinity, for instance
Earth being many times more massive than all of the NEAs combined, and
Neptune "dwarfing" Pluto and the rest of the KBOs.[3]
Stern and Levison's paper shows that it is possible to estimate whether
an object is likely to dominate its neighborhood given only the object's
mass and orbital period, known values even for extrasolar planets. In
any case, the recent IAU definition specifically limits itself only to
objects orbiting the Sun.[1]
..
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