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IAU Proposes 3 New Planets
IZ Reloaded writes "Sources tell SPACE.com that the International Astronomical Union is preparing to include three new entries to the current list of planets in our solar system. From the article: The asteroid Ceres, which is round, would be recast as a dwarf planet in the new scheme. Pluto would remain a planet and its moon Charon would be reclassified as a planet. Both would be called "plutons," however, to distinguish them from the eight "classical" planets. A far-out Pluto-sized object known as 2003 UB313 would also be called a pluton."
We need a planetary definition so we can communicate efficiently. Why else do we need words. Try talking about your environment without classifications of natural objects:
I bought my direct ancestral animated entities an animated entity with four appendages used for walking, one appendage for knocking down lamps, a soft covering that is white with black spots, which speaks in guttural exclamations which are just nonsensical to animated entities like myself.
Instead of:
I bought my kids a dog
As our observations of our environment reveals new information. We must periodically change our definitions to attempt to make our abstractions best reflect reality.
I completely disagree with that the current system is better, but I don't see why your question merits the moderation (-1, Troll).
It's completely unsatisfactory to talk about "planets" when we don't know what is meant by a planet. Simply enumerating the ones in our solar system makes it very clear for our system, as we did so far, gives clarity for our solar system: the nine ones are planets, all others aren't. It doesn't state a reason. If asked why Pluto is a planet, and the very similar 2003 UB313 ("Xena") isn't, all we can say is: "historical reasons" or "convention".
When describing other solar systems, it is very normal to describe celestial bodies which are similar to the planets of our solar system, as "planets". But when is a body sufficiently like a planet of our own, to merit this description?
Really, it was high time we got a workable definition. Anything. Anything is better than an enumeration.
So, the International Astronomical Union (IAU) currently holds a highly-anticipated conference on the definition in Prague. It started last Monday, and a final decision is expected by next Thursday August 24, 2006.
The current proposal is:
It has the added benefit that the minimum size (to exclude most Kuiper belt objects etc.) is not an arbitrary number, but a physical condition. The shape of objects with mass above 5 × 10^20 kg and diameter greater than 800 km would normally be determined by self-gravity. In borderline cases, we now must observe the roundness.
The pluton definition does have an arbitrary figure in its proposed definition: orbits around a star that takes longer than 200 years to complete.
But according to an article by Isaac Asimov (Just Mooning Around from Of Time and Space and Other Things), the Sun pulls the Moon twice as strongly as the Earth does, and the Moon's orbit, drawn to scale, is always concave toward the Sun, making a very convincing argument that the Earth and the Moon are a double planet system, even though their center of revolution is a thousand miles beneath the Earth's surface.
If Charon is to be classified as a minor planet, the Moon should be too.
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The term "dwarf planet" is actually starting to grow on me. It still keeps Pluto as a planet, for those who absolutely need it to be a planet, but really it IS a demotion to a status equal to the larger asteroids & KBOs. The way I see it, the Solar System has 8 Major Planets (4 terrestrial, 4 gas giants), at least 50 Dwarf Planets (Pluto, Ceres, 2003 UB313, etc) that are round due to self-gravitation, and the non-round objects can still be called Minor Planets. It just adds an intermediate classification between "planet" and "asteroid/minor planet".
The "debate" is basically a media event, based on people who take their grade-school science classes too seriously, and think that for some reason that the Solar System must contain exactly nine "planets".
I think that one of the problems in this country (the US) is that we do not take grade school science seriously enough. We need those science classes to engage the kids and hopefully inspire some of them to a career in some scientific field.