Quote:
Originally Posted by Tachyon
What's laughable? Frankly, I have read this forum for days and I can't find a scientific reason from those who are against the IAU resolution. It seems that many here are unable to see why the Kuiper and the asteroid belts are called "belts".
Ara Pacis, Triton is orbiting Neptune, which means that the gravitational influence of the latter makes Triton a satellite and not a wandering "dwarf planet", thus Neptune has cleared Titon from its own orbit.
Yes, there are many KBOs near Neptune's orbit, but that doesnīt mean it "hasnīt cleared its orbit", since these bodies, including Pluto, are in some kind of orbital resonance with neptune.
But please, donīt mention trojan asteroids anymore, since , as it's been said so many times before, the mass of all these asteroids is inferior in many orders of magnitude to Jupiter's or Neptuneīs mass.
The IAU resolution is not perfect: no decision on this subject will ever be perfect, buy it's the best I can imagine, especially compared to the strange alternatives I've read on this forum.
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The concept of clear is, itself, not clear. The past tense, "used", suggests a static present, and the action of Neptune and Triton belies this. It's a minor nitpick, but the larger issues of claiming clear = resonance are still unresolved. I think there are many scientific arguments against the current theory. Of course, scarcity in direct assaults on it are probably due to the lack of specificity in the definition. In other words, the new definition is hiding in ambiguity and claims the classic eight by fiat, not by examination.
It comes down to the science of communications and taxonomy, as both the first proposal and the adopted proposals have science to support them. I still think location is a second (or lower) order classification level for objects. A Hydrostatic Equilibrium is just as scientific and provides a brighter line. HE may be fuzzy, but objects are either above or below that physical and empirically derived limit. "Clearing a neighborhood" is currently undefined, but most unofficial arguments suggest orbital or mass dominance criteria for it. The definition of clear will probably end up being a mish-mash of several criteria, some of which may even be contradictory.
Contrary to what some have suggested, "clearing the neighborhood" is not just about mass and gravity. Tidal effects are related to spin. Time between encounters is dependent upon period. Gravitational slingshot is related to orbital speed. When an object is in a slower orbit it has less speed to imbue upon a passing object which would cause it to "clear the neighborhood". In other words, "clearing the neighborhood" is not something a planet does, it's an act the sun performs using one object upon another. If an object's gravity was the only determinant for "clearing the neighborhood" then accretion would be the only logical result, since ejection relies upon more mechanisms and forces than an object's gravity.
Again we come to my primary disagreement, which is that orbital elements define systems and are, therefore, systemic properties, not inherent properties, and I think a definition of a planet should be inherent. A planet should be defined by
what it is instead of
where it is.
Those people who want to argue about what a belt is should look at one. The Kuiper Belt is 2/3 the radial width of the entire up-wind solar system (30AU v. 20AU), and contains almost twice as much planar area (8,873sqAU v. 15,775sqAU). The Kuiper belt is a belt in the same sense that a boilersuit is a belt because it goes around the body. These are not narrow bands but vast regions. Discarding some objects because they exist in these regions of non-empty space makes little sense when you realize the 4 inner "planets" occupy a region with the same radial width as the "asteroid belt" (about 1.2AU for both). However, they have not been discarded because one has not cleared out the other three, outmassed the other three, or cast the other three into resonances. I would say the IAU resolution is inconsistent, except that they have not yet defined what consistency is.