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Comments: 426 +- Science: IAU Demotes Pluto to 'Dwarf Planet' Status on Thursday August 24 2006, @09:38AM
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davidwr writes "It's official. Pluto's been demoted. It's now one of several 'dwarf planets.' I guess we can drop the 'Period' from 'Mary's violet eyes make John stay up nights.'" (Of course, no one says you have to privately agree with the International Astronomical Union.) Several readers have contributed links to the BBC's coverage of the downgrade, as well as the usefully illustrated story at MSNBC.
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my take on it: (Score:5, Funny)
Re: (Score:3, Funny)
Re:my take on it: (Score:5, Funny)
Parent
Re:my take on it: (Score:5, Informative)
I wouldn't call it a screw-up.
The draft proposal was:
Pluto would continue to be a planet, and Ceres, Charon and 2003 UB313 would become planets. However, this criterium is reached by hundreds, even thousands of other celestial bodies in our solar system. Under that proposal, all could gain planet status.
The final text is:
This definition does not define the terms "nearly round", nor "neighbourhood". But having a definition, rather than just an enumeration, is in my opinion a big leap forward. Demoting Pluto is a small price to pay.
I quite like the additional criterion of dominance of a body in its neighbourhood. It's not as arbitrary as simply requiring a minimum mass or size.
On the other hand, I do not like the fact that a planet should orbit to Sun to be called a planet. On this point, I preferred the original proposal in orbit around a star. I don't see why our solar system should be any different, why planet-like celestial bodies orbitting other stars are not called planets.
Parent
Re:my take on it: (Score:5, Interesting)
Pluto orbits the sun, but it also orbits a point in space above its surface. Charon doesn't orbit Pluto, but orbits a point in space above the surface of Pluto, while it too orbits the sun. Can someone explain to me why this shouldn't be called a double?
Parent
Re:my take on it: (Score:4, Interesting)
"is not a satellite" does not exclude Charon, because they picked a somewhat peculiar definition of "satelite" (barycenter of gravity inside the primary), which excludes almost everything we typically think of as a moon, but not Charon. This definition makes the Moon a satelite, but if the Earth had a slightly smaller radius but the same mass, the Moon would follow exactly the same orbital track, but suddenly be a planet.
I beleive they picked this definition of "satellite" specifically to exclude Earths Moon. If you actually plot the orbital tracks of the Moon, Charon, and any other moons you like, one stands out like a sore thumb as the one that should obviously be said to be orbiting the Sun. It's not Charon.
Parent
Re: (Score:3, Interesting)
They claimed to exclude Charon from being a dwarf planet, so they're obviously not using the barycenter definition to determine what a satellite is.
Re: (Score:3, Insightful)
Not that it really matters all that much. As other astronomers have commented, they mostly just say "body" and give a list of specs. Terms like "planet" are a bit too vague to be useful as technical terms. After all, Mercury
Re: (Score:3, Insightful)
.. but given enough time... (Score:3, Insightful)
But isn't the Moon's distance from Earth slowly increasing thus, surely, the binary planet definition will also apply to the Earth+Moon eventually?
Re:.. but given enough time... (Score:4, Informative)
Actually (if I did the math correctly) in about 3,529,037,195 years. That's still within the projected lifetime of the solar system, so yes
Parent
Re: (Score:3, Insightful)
Legal issues.
If we get off this rock, we will probably allow asteroid mining. It would then be OK to reduce an asteroid to rubble to extract the ore that you want. Now imagine Pluto has some valuable Ultra-rareium at its core. Is it OK for a company or a country to smash it to pieces?
These definitions are important so laws can be made. Is it OK to bury radioactive waste in an asteroid? What about Mars? Does this apply to all planets, or
Re: (Score:3, Informative)
> Sun to be called a planet. On this point, I preferred the original
> proposal in orbit around a star. I don't see why our solar system
> should be any different, why planet-like celestial bodies orbitting
> other stars are not called planets.
Because they're only defining what a Solar planet is, not the general meaning of the word "planet":
The IAU therefore resolves that planets
Mutually exclusive (Score:3, Funny)
Sorry, I should have said mutually exclusive set. Really wikipedia has a good diagram, but the orderly diagram makes it appear to be a logical distinction rather the linguistic mess that it is.
A: Pluto is a planet
B: No, Pluto is a dwarf Planet.
A: Yes, that's right I said it was a planet.
B: But it is a dwarf planet, so you are wrong.
A: Isn't a dwarf planet just a type of planet?
B: No.
A: Then why is it called a planet at all
B: uhhh, cause
Re:my take on it: (Score:5, Funny)
What's he going to do now?
Parent
Re: (Score:3, Insightful)
I agree...screw Neptune.
Re: (Score:3, Funny)
Re:my take on it: (Score:5, Funny)
At a rate of once every six days, nine hours, seventeen minutes, and thirty six seconds.
Parent
Re: (Score:3, Insightful)
Clyde Tombaugh is surely spinning!
In astronomy, they don't call it spinning, but "ro...tat...ing" (making finger quotes as I type). You have to give some respect to the man who discovered the biggest snowball that side of the asteroid belt
Mnemonic device update (Score:5, Funny)
Now every geek's question is... (Score:5, Funny)
Re:Now every geek's question is... (Score:5, Funny)
Parent
Astrologers panic! (Score:5, Insightful)
So will this render all astrological predictions which took Pluto into account as invalid? I'm sure the kooks will come up with some excuse to explain how their previous charts were accurate at seeing the future as if they ~knew~ this all along.
Re:Astrologers panic! (Score:5, Insightful)
Parent
Re: (Score:3, Informative)
Then again, when you're dealing with flimflam you can pretty much say whatever you want.
The fact that NPR had this segment only served to legitimize this nonsense and continued to give hope to the gullible that astrology is valid.
A new one (Score:5, Funny)
Why is this "breaking news" (Score:4, Insightful)
Now that would be breaking news!
Re:Why is this "breaking news" (Score:5, Funny)
Parent
Pluto demoted? (Score:3, Funny)
That changes everything (Score:5, Funny)
Re:That changes everything (Score:5, Insightful)
Parent
So why does Neptune qualify? (Score:5, Interesting)
Re: (Score:3, Insightful)
Re:So why does Neptune qualify? (Score:5, Informative)
Parent
Re: (Score:3, Informative)
http://www.google.com/search?q=pluto+neptune+reson ance [google.com]
http://en.wikipedia.org/wiki/3753_Cruithne [wikipedia.org]
Re:So why does Neptune qualify? (Score:5, Informative)
Parent
Re: (Score:3, Informative)
Son of a B*****!!! (Score:3, Funny)
Teaching about Pluto in School (Score:3, Interesting)
I got in similar trouble to telling my teacher that her solar system model was wrong because all of her planets were on the same plane. And, got in more trouble when I mentioned that Pluto is not the furthist planet from the sun, but rather Neptune was (at least, at that time). Of course, the worst was when I corrected a teacher whom said Saturn was the only plane
Courtesy correction to terminology (Score:3, Funny)
Actually, "dwarf planet" is considered rude.
It prefers to be called a "little planet".
(And besides, if Pluto is going to be the dwarf planet, which planet do the elves get? Or the hobbits? Won't someone think of the hobbits?)
Napoleon... (Score:3, Funny)
I don't like this at all.
You IAU bastards! Now, My Very Educated Mother no longer Just Sat Under Napoleon's Picture. Now, My Very Educated Mother Just Sat Under Napoleon.
You guys are sick. Leave my mother out of this.
Holst was right. (Score:5, Funny)
Anyone? Anyone? (Score:4, Interesting)
Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's.
1) - Is it possible for Pluto and Neptune to one day (like within the next couple billion years) collide? Or are their respective orbits degrading to the point where by the time they'd be near each other orbit-wise, their orbits would no longer overlap significantly? Or by 'overlap' do they mean "diagrammatically speaking, on a two-dimensional representation they overlap but even at their closest possible point they're still a squillion miles away from each other"?
2) - If so, how cool would that be? Would it be funny enough to make it onto an America's Funniest Home Videos video montage? Would it need special clown-horn-honking sound effects?
3) - Considering their distance from Earth and their relatively small size, would a collision of the two have any noticeable effect here on Earth?
4) - Seriously, how cool would worlds colliding be?! Costanza jokes aside, I think it'd be awesome to the max.
Re:Anyone? Anyone? (Score:4, Informative)
Is it possible for Pluto and Neptune to one day (like within the next couple billion years) collide?
Nope. Their orbits are in 3:2 orbital resonance [wikipedia.org]; basicly this means they constantly miss each other (a bit like your average commuter bus and train schedule :P). Also, due to the declination of the Pluto orbit it doesn't even touch the Neptune orbit. When seen straight from above, the orbits overlap, but if you go off-angle to just the right spot the Pluto orbit can be seen to be completely separated from Neptune.
Parent
Pluto and Neptune (Score:3, Insightful)
Doesn't that mean that Neptune also hasn't cleared it's neighborhood? It's orbit overlaps that of Pluto. So why is IT a planet?
Re:Stupid (Score:5, Insightful)
Given the level of scientific illiteracy, what the hell is the point of taking something that everyone does know and declaring it to be wrong?
"Everyone" knew there were eight planets prior to 1930. Did the world end when it was changed to nine, especially with something that wasn't even obviously a planet?
Guess what? A whole generation of children will grow up with the new, consistent rules and won't know any different. What's unarguable is that the new rules are better. I'm all in favor of fixing things that are broken, even if certain curmudgeons are too mentally inflexible to make the adjustment. See also: the metric system in the US, which is kept down by the same curmudgeons.
Parent
Re:Ok, so no we have... (Score:4, Funny)
Parent
Re: (Score:3, Informative)
Re:my take on it: (Score:4, Interesting)
I'm assuming for the moment that it was misreported. The real problem with Pluto is the thirteen other known Plutinos -- objects not gravitationally related to Pluto, but also in highly elliptical Neptune-cossing orbits with a 3:2 resonance to the Neptunian orbit.
Now, there are a bunch of objects which have stable solar orbits with a period the same as Mars. But in the case of Mars, they all either orbit Mars itself, Sol-Mars L4, or Sol-Mars L5. Same can be said for Jupiter, Saturn, Uranus, and Neptune (and Earth, except the "bunch", since Earth only really has the Moon).
Instead, Pluto is like Ceres, which has a number of objects in the same orbit which are all more-or-less doing their own thing. Demoting Pluto now that we know about the Plutinos is like the demotion of Ceres after the discovery of a bunch of other asteroids in the same orbit.
Parent
The problem is that the public wasn't right. (Score:3, Insightful)
No. We've known for decades that the "planet" Pluto was far smaller than any other planet and made of fundamentally different stuff. And through all that time, astronomers let it go because every time one of them mentioned that Pluto wasn't really a planet he was shouted down by the public. Now that we know there are dozens of bodies just like Pluto - and some even larger - what little scientific ac