[EMAIL PROTECTED] wrote:
>
> In a message dated 3/15/2004 8:31:53 PM US Mountain Standard Time,
> [EMAIL PROTECTED] writes:
>
> > Is there some real consideration that planetoid will officially be
> > considered a planet, or was it just newspaper cluelessness?
> >
> > -bryon
> >
> >
>
> In the full article I read, the new definition of a planet, as defined by the
> finders of the object is this:
>
> A planet is any body in an orbit where the object's mass is greater than the
> combined mass of all the other bodies occuping the same general orbit.
>
> Making Pluto a planetoid.
>
> As to newspaper cluelessness, even the local TV news was calling Sedna a
> planet.
>
> And this is Tucson, damn it!
>
> William Taylor
A competing definition of a planet is "a body whose shape is determined by its own gravity", or something to that effect, which would make both Sedna and Pluto planets, but would leave asteroids, etc. off the list. They might get classified as minor planets, making the big'uns major planets...
By that definition, Ceres probably qualifies as a planet, but the others are too small and irregular in shape.
Also, Kuiper Belt Objects such as Ixion, Varuna, Quaoar, and a number of others which have no names yet, just numbers, would qualify, and there will likely be more KBOs and Oort Cloud members found that are in that size range (or perhaps larger, maybe as large or larger than Pluto, even), which means that the list of "planets" would likely be in the dozens or even the hundreds in the not too distant future. And what about bodies such as the four Galilean moons of Jupiter, Titan, and even our own Moon, all of which are significantly larger than Pluto, not to mention Triton, which is just barely smaller than Pluto? Only the fact that each of them orbits a larger planetary body which orbits the Sun rather than orbiting the Sun independently leaves them our of consideration. In fact, most textbooks count our Moon as a fifth terrestrial planet, along with Mercury, Venus, the Earth, and Mars, because geologically and structurally it is more similar to those bodies than to any other class of bodies we have studied.
This should be an interesting debate to watch over the next several years.
It already makes for some interesting, as well as lengthy and ultimately unsatisfying, discussions as to "How many planets are there in our solar system?"
Somewhere Between A Low Of Eight And A High Of Who Knows Maru
-- Ronn! :)
Ronn Blankenship Instructor of Astronomy/Planetary Science University of Montevallo Montevallo, AL
Disclaimer: Unless specifically stated otherwise, any opinions contained herein are the personal opinions of the author and do not represent the official position of the University of Montevallo.
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