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Martin

Pluto is out---only 8 planets now---it's official :(

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I think the decision of not considering Pluto as a Planet is not justified. They will now consider it as white dwarf. The definition also lays out a third class of lesser object that orbits the Sun-"small solar system bodies."(A term that will apply to numerous asteroids, comets and other natural satellites.)

Do you all think that it is a real justification?

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I think the decision of not considering Pluto as a Planet is not justified. They will now consider it as white dwarf. The definition also lays out a third class of lesser object that orbits the Sun-"small solar system bodies."(A term that will apply to numerous asteroids, comets and other natural satellites.)

Do you all think that it is a real justification?

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I think we really should just go with it and say their could be a few dozen planets in our solar system' date=' we could just call the 8 "inner" planets the core planets. and omit the rest from general knowledge requirements

[/quote']

 

That's essentially what they did. Except they renamed the outer ones and not the inner ones. I disagree with you on the general knowledge though, we should be teaching every fifth grader that not only are there eight large planets, but two asteroid belts (with large objects in them), many satellites and all kinds of comets and other miscellaneous objects. It seems to me, (admittedly my only evidence is my own elementary school education) that we don't do enough to make children wonder at the colossal beauty of nature.

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Oh snap, now the disenfranchised astronomers who weren't able/willing to vote on the final resolution (where only some 424 out of about 2500 astronomers attended) are having a backlash against the IAU.

 

As Dr. Alan Stern, head of NASA's New Horizons mission, points out, the resolution's definition for "planet" isn't consistent with those considered one now and excludes Earth, Mars, Jupiter, and Neptune, the first three on grounds of various asteroids which cross or occupy their orbits and in the latter case because of Pluto. As it is, any astronomer should have been aware of these asteroids and I don't think there's an excuse for a scientific definition to even leave such things under debate.

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I think a good arbitrary definition of a major planet would be that it must be larger than our moon. That would get rid of the ambiguous "cleared it's path/dominant" part. Moons would still be excluded and Pluto would still be out so it wouldn't change anything at present.

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Germans ought to be disgusted by the change because they have this

mnemonic

 

Mein Vater Erklärt Mir Jeden Sonntag Unsere Neun Planeten.

 

now their mnemonic is spoiled. :)

 

http://de.wikipedia.org/wiki/Mnemotechnik

In combination with that link that´s a funny statement. You are right, that mnemonic is widely used and it´s also how I remember the order of the planets. However, Wikipedia seems to be very fast at adopting to changes that make some publicity. The article you linked to has already changed and the new mnemonic is now "Mein Vater Erklärt Mir Jeden Sonntag Unseren Nachthimmel". It might be the form it had before the discovery of Pluto. But it might also be that the change was made simply by some creative person. In that case, given the high number of visitors Wikipedia gets, we might have witnessed the birth of a new mnemonic. Not that this will have much historical consequences, but given that social/cultural scientists sometimes do a lot of research to figure out where a saying comes from, I find it interesting to see the birth of one.

 

EDIT: I wanted to ask the person who changed the Wikipedia article about how he came up with the new sentence. Sadly, the change was made by an IP which does not seem like a permanent IP. I had really liked to know how he/she came up with it, but now it seems I´ll never know.

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the old mnemonic was also in the German wikipedia article on the Solar System. you may wish to look at that and see if it has been changed there too, and by whom

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The article on the solar system only states "there were proposal for new mnemonics like ...". At least there is a reference to the old version of the mnemoric and it wasn´t the Nachthimmel-version.

But it seems that I was too fast in judging that "Nachthimmel" will be it because it´s written on Wikipedia - there seem to be discussions going on. Chances are that a discussion about it might even make it to the yellow press or "yellow tv".

I like the "Mein Vater Erklärt Mir Jeden Sonntag Unsere Neudefinition"-version (= "... our new definition") but it probably has little potential to become a classic.

 

EDIT: It´s funny to see that a rather irrelevant thing such as whether to call Pluto a planet, a dwarf planet or a gremlin leads to such a noise - just because for one time in science, everyone has the feeling to know what´s being talked about (I personally don´t feel like I knew what´s being talked about, btw). http://www.spiegel.de, a very frequently visited news page already calls for people to send them proposals for new mnemonics. I suppose the same thing happens in english-speaking countries, too.

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So how many dwarf planets are there, then? Just Pluto, Charon, and Ceres? What about the other large Kuiper belt objects, like Sedna?

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Sisyphus, did you check out this by Mike Brown, maybe it says something.. I would estimate we are looking at eventual possible 50-200 "dwarfies" being found, like sedna, xena, etc.

 

 

Here is something of his called What is a Planet?

http://arxiv.org/abs/astro-ph/0608417

published in Annual Reviews of Earth and Planetary Science 2006 v. 34

 

 

I cant read everything. If you read this article, let us know if it says anything relevant to your question.

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Here is something of his called What is a Planet?

http://arxiv.org/abs/astro-ph/0608417

published in Annual Reviews of Earth and Planetary Science 2006 v. 34

 

 

)

 

Note the idea of using a historical definition. Pluto and anything bigger would be "in".

 

It might be interesting to have a "minor planets" definition in this way. Pluto and Xena would qualify, and anything smaller would be dwarfs, asteroids etc.

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I dislike the historical definition. Having Pluto grandfathered in but nearly identical objects not counted just seems silly to me. I like the other definition offered:

 

planetary mass object, or planemo: any object big enough to be round but small enough not to undergo fusion at any point in its existence

 

fusor: any object big enough to undergo fusion

 

planet: a planemo that orbits a fusor

 

This, naturally, would include probably dozens or even hundreds of yet to be discovered Kuiper Belt objects, but there could be other distinctions as well, based on size or circumstance. Earth, for example, is clearly master of its territory, having more or less cleared the area around its orbit. Pluto, on the other hand, is not, and is one of a population of similar objects. Call it a "minor planet" or a "Kuiper planet" or something.

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I adore Pluto, and I've also read it's the most adored by kids around the world, so I was quite dissapointed to see it removed from the list. But.. then something struck me.

 

This is just a definition. I mean, the fact we include or not include it in our definition set of "planets" doesn't mean it has changed in any way.. or.. that it isn't THERE.

 

It is what it is, whether we call it Pluto the Planet, or Pluto the cutest-celestial-object-in-our-solar-system..

 

I just had to share hehe it seemed to me that people respond emotionally to this desicion, but scientifically i can't find any way it actually affects it. It was, always, a controversial "planet".. everyone who learns astronomy knows it was called one, but it isn't really behaving like one.. Its not that it's new..

 

Anyways, those were my 2 cents :)

 

~moo

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As soon as I read this new definition I liked it better than the other proposed one (because it got rid of Pluto and wont bury us under tiny planets), but I notices that the criteria of "clearing their orbital area" is pretty vague. There is a lot of stuff floating around in earths orbital area, is that cleared? What about Jupiter?

 

My problem with the previous definition was the arbitrary use of the word spherical, that you needed an actually numerical definition for spherical when used with the definition. But this clearing orbital area is super vague, and needs to be better defined. I'm not sure how they're going to do that, since there has got to be a decent amount of mass floating around in Jupiter's orbital field. Maybe exclude Lagrangian points, allow those to have mass in them which you dont include in the rest of the definition.

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Personally im glad that pluto isn't considered a main planet anymore, but i dont like the idea of the 'dwarf plants' which are mostly just large objects in the kuiper belt, if you consider pluto a planet then theres a lot of other objects that you could too. (btw charon and pluto are now considered a binary system because of charons gravitational effect on pluto)

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The IAU definition of "clearing the neighborhood around its orbit" is a bit vague. This article ...sheds some light on the subject.

 

Good pick. Stephen Soter "What is a Planet"

 

if anyone wants the abstract (short summary) instead of the whole download, it is here

http://arxiv.org/abs/astro-ph/0608359

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