Re: Toward a Rational Definition of what is a Planet

How about we forget about trying to keep Pluto as a planet. Pluto has
significantly lower mass than at least 6 of the solar systems moons and is
part of a large population of bodies (the Kuiper Belt) that includes objects
of similar size to Pluto.

Setting the lower limit of a planet to Pluto's size would put Pluto, UB313
and who knows how many other objects to a higher status than many moons.
This wouldn't be wrong if it wasn't so arbitrary. Setting the lower limit
the minimum mass for sphericity would be impractical because it would
include too many objects.

Therefore I think the mass of the solar system's largest and most massive
moon, Ganymede, (but not its size, that would exclude Mercury) should be set
as the lower limit for the mass of a planet. Anything smaller but still
spherical is a planetoid.


On 26 Sep 2005 21:42:56 -0700, edward12@xxxxxxxxxxx wrote:

|Why not just say that anything smaller than Pluto is just a "Minor
|Planet" and anything Pluto's size or larger is a Planet?
.

Relevant Pages

  • Re: Overall disappointing...
    ... the most puzzling was the fact that Lowell had predicted that Planet X ... would have a mass 6.6 times that of Earth. ... Labeling Pluto as a Planet was a huge long-term mistake and I am glad ...
    (sci.astro.amateur)
  • Re: Strength of Materials
    ... orbit around the Sun, has sufficient mass for its self-gravity to ... "If Neptune had cleared its zone, Pluto wouldn't be there," he added. ... content to keep Pluto as a planet, and, when you discover something new ...
    (sci.physics)
  • Re: Planet Definition Revisited
    ... not seem to be anything particularly special about Pluto that warrants ... making its mass the dividing line. ... That others may differ goes without saying. ... to be able to decide, in a timely fashion, whether something is a planet ...
    (sci.astro.amateur)
  • Re: "Pluto Now Called a Plutoid"
    ... Neither of these measures is mentioned, even indirectly, in the IAU's resolution regarding Pluto or any subsequent IAU resolutions. ... "There are no other objects greater in mass than Ceres within 2 au." ... Soter's paper gives a fairly decent basis for determining whether the neighbourhood has been cleared in the concept of the planetary discriminant; the ratio between the mass of the body and the total mass of the other non-resonating and non-satellite bodies in the same orbital zone. ... The two different papers give markedly different definitions of clearing the neighbourhood but identical results, indicating that what we have done is apply the label planet to a natural class. ...
    (rec.arts.sf.science)
  • Re: Overall disappointing...
    ... The discovery of Pluto led to many questions about the planet. ... would have a mass 6.6 times that of Earth. ...
    (sci.astro.amateur)