CNN does a decent intro, although I'd suggest digging in a bit deeper than that.

Personally I like applying 12th planet theories to this, which would state Pluto is an ex-moon of saturn and not a planetary body itself... But hey, thats my theories ^^

Personally, I'm very happy with what I read on the lead article on space.com, that they apparently plan on adopting the definitions terrestrial planets, giant planets and dwarf planets. Well, that's not certain but seems likely. On the other hand, this definition too will become muddied as we see hybrids of these eventually pop in other solar systems. Perhaps planets like Earth but five times larger and with quadruple the atmospheric density?

Another jinx coming up in the system is the detection of Planemos

I believe a planet is the formation of a large body with its own orbit its host star, small enough that it does not have any internal nuclear processes, but large enough for its own geological activity and such. The threshhold for small enough is of course very scientific and reasonable. The small enough is hard to gauge and arbitrary.

[ 14 August 2006: Message edited by: 500_Apples ]

[ 14 August 2006: Message edited by: Bobolink ]

And so, for those who find semantic arguments boring, here's an animation of the destruction of the Earth:
http://www.youtube.com/watch?v=yYgEwXWilUc

Bad Astronomer pointed out that as the shockwave from the impact converged on the point of the Earth opposite the impact site, there would be a plume of material getting ejected. Otherwise he thought it was accurate.

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Perhaps planets like Earth but five times larger and with quadruple the atmospheric density?

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To our current knowledge, it is speculated if such an object could even form... When a planet forms from a cloud of gas orbitting a sun (once again purely speculation as we really have little understanding of how this fully works), you are working with a limited amount of material. Larger planets form further out (larger orbit means more material to form from) from less dense material. Earth, and any planet containing earth like qualites, are really limited to the inner circle of planets (very much to do with densities... Earth has a solid iron core at it's center. Iron being one of the most dense elements that form in the fusion process will only be present around the inner rings). Although the search for an earthlike planet is likely moot anyway... Life could just as easily be found on a very unearthly planet.

Thanks for that planemo link... Thats an interesting phenomenon. I think it must be recognized that we have absolutely no clue how planets form and that our solar system is potentially one of a million possibilities in initial planetary formation. I'd be really interested if they can make any informed speculation at the composition of this 'Planemo'

Personally, I think 'planet' status should be founded on the planets formation and composition (the mainstay is the presence or absence of the Iron core which represents inner or outter planetary formation within our solar system setup)... And then secondly on the composition of the formation. The coposition is quite telling of how a body was formed... A body with a significant 'heavy' core, such as Earth's Iron core, or Jupiter/Saturn (srry, cannot recall what the core compotion is off hand) means that it went through a planetary formation process. A body that lacks this would likely mean it formed differently than to our understanding of planetary formation. The problem with this style of classification is I'm attempting to classify based on unknown or speculative information

[ 15 August 2006: Message edited by: Noise ]

Added : Mind you, it's completely up in the air why our asteroid belt formed (minus something like 12th planet theories ^^), and estimations say we're missing about 50-60% of the mass that should really be there... It likely was inner planet composition (iron heavy), so it's possible a larger earth like planet can form in either case.

Theres enough other strange oddities... How did the Earths moon form? It has a similar makeup to earth, except only a tiny iron core... Leading itself to the theory that the moon is a fragemented chunk from Earth.

Should as as an FYI... Iron cores are known from 2 peices. Any planet with a magnetic field requires iron in the core. The size of this core is extrapolated using mass and densities (calculated by orbits/speed)... So alot of this information is extrapolated/speculation and not truely known. I think mercury was 90% iron?

[ 15 August 2006: Message edited by: Noise ]

Wikipedia provides a good overview of the planets. Mercury's iron core is about 70% of the diameter.

Venus is what happens to a planet that has too much CO2 in the atmosphere ^^

[ 24 August 2006: Message edited by: Noise ]

[ 24 August 2006: Message edited by: Noise ]

The debate is now over: It ain't a planet.

They now have a new category: "dwarf planets". I guess soon we can look forward to Pluto's being joined by overgrown asteroids named Happy, Dopey, Sleepy, Grumpy, Sneezy, Bashful and Doc.

[ 24 August 2006: Message edited by: M. Spector ]

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From now on, smaller round objects orbiting the Sun — including the asteroid Ceres, the former planet Pluto, and the Kuiper Belt iceball with the provisional designation 2003 UB313 — will be called "dwarf planets." The explicit intent of the IAU members who voted with the majority today was that a "dwarf planet" is not a planet

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Added:
From the wikipedia one venus:

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Studies have suggested that several billion years ago Venus' atmosphere was much more like Earth's than it is now, and that there were probably substantial quantities of liquid water on the surface, but a runaway greenhouse effect was caused by the evaporation of that original water, which generated a critical level of greenhouse gases in its atmosphere.[9] Venus is thus an example of an extreme case of climate change, making it a useful tool in climate change studies.

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[ 24 August 2006: Message edited by: Noise ]

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Originally posted by Jimmy Brogan:
Great leaps forward in understanding have occurred in chemistry, biology, and astronomy among other sciences just from the act of meaningful classification.

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Only because those classifications reflected natural divisions.

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but the controversy over it makes no sense at all.

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Within the astronomy community, the contreversy makes sense as it's creating definitions.

The earth's mass is some eighty times greater than the moon's mass, and the center of mass is deep within the earth, as such I wouldn't call it a double planet.

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Well, now we are going to have to determine wether size really does count, and Titan, Triton and Ganymede.

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Theres a few more of great size that can probably make this list too... But by definition they are natural satelites. A planet must orbit a sun, while a satellite (moon) orbits a planet.

For the earth-moon (what makes the distinction of say, pluto), is the earth holds the moon in tidal lock, while the earth's rotation is independant of the moon (the result is the same side of the moon faces Earth). Pluto-Charon are both within a constant state of tidal lock (meaning the same side of Pluto is always facing the same side as Charon).

Personally, I think the definition should be regardless of size and dependant entirely on the environment in which they formed.

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a lot of current thinking is that it's current greenhouse state may have actually been related to too many volcanoic eruptions

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Hehe, we can get into Venus states if you want... One big notable is the complete lack of a magnetic field. It's magnetic field, like Earths does now, would have protected it from solar winds and other harmful rays from the sun. Without this magnetic field, those rays would evaporate any water and send the temperatures soaring like you see today. The other notable difference is the odd rotation (~115 days) and in the reverse direction of it's rotation compared to other planets. That, along with the tidal lock posiibility with earth (earth passes it's closest point with venus ever 584 days here on earth, or exactly 5 days on Venus) you can draw some conclusions.

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Some argue that if Pluto kept its crown, Xena should be the 10th planet by default -- it is, after all, bigger. Purists maintain that there are only eight traditional planets, and insist Pluto and Xena are poseurs.

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Well that's a real winner! Planets as poseurs. What's next? Lying nebulas?

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"We of course need the definition of a planet first."

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Hold on a minute. They just offered a definition in the first quote. How do they know there are "eight traditional planets" if they can't yet define what a planet is?

I'm no astronomy expert for sure. But when I was in grade school and very interested in space sciences, it was understood that if it had an atmosphere, solid mass, weather systems, a rotational axis (which means polls, and especially if it has an atmosphere, polar caps) and a fixed orbit pattern, then it pretty much was a planet.

If read the various articles on this correctly, Pluto has these same features. So why can't it be a planet?

It adds the Hubble Telescope says Pluto is slightly smaller that the moon. That's actually makes it not much smaller than Mercury. Yet no one disputes that Mercury is a planet.

One reason for de-listing Pluto as a planet is that many astronomers feel if it continues to be considered a planet, the recently discovered celestial object, known as either Xena or Lila, might have to be considered one as well.

The question is does Xena have similar features as Pluto or the other eight "traditional" planets? If it does, then why can't it be considered a planet too?

Is there something cosmically wrong with having ten planets in the solar system? We have had nine up until now, and the universe really doesn't seem to care.

Other stories I have read say there are three additional objects as well that might have to be considered planets as well if Pluto remains classified as a planet.

I say so what. If they meet the above criteria, why not have them as well? Or did I miss something along the way that there's some rule similar to immigration quotas only for planets?

Or perhaps there's some sort of systemic discrimination at work in the astro-physics community against smaller planets.

The head of the International Astronomy Union says there's no question the bigger planets are actually planets because they are gas giants.

Well, with due respect, he kind of looks like a gas giant himself. The fact is, if the big planets, like Jupiter, which have atmospheres and weather systems and rotational axises and fixed orbits, etc, can be considered planets, then I say the smaller ones with similar qualities can be as well.

Think of this. Jupiter and Saturn and the other big gas giants likely don't even have hard soil surfaces, as the atmospheres just get thicker and denser the closer you get to the center.

So no matter how big they are, you will never get the chance to walk on them. Yet they are considered planets. Pluto does have a hard soil surface that the Voyager craft even photographed on its deep space fly-by. Yet it gets kicked out.

That's unfair.

I would like to go to that big conference of self-absorbed stargazers and tell them that if size is the big thing that matters in defining what a planet is, then we should just de-classify the Earth as a planet as well, since it's so puny compared to the "Big 4" (Jupiter, Saturn, Uranus and Neptune).

We can then re-classify ourselves as a cosmic RV with its own portable polls, showers, toilets and mineral water, that's stuck permanently in a one-way no-passing zone around the sun.

Dirt Bags

And, I guess I'll have to say it, since nobody else has yet:

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Originally posted by Ken Burch:

"It's not the SIZE of the planet, it's what you do with it".

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Originally posted by unionist:

Yeah, and the problem with Pluto was apparently that is was frigid, doing nothing but go round and round.

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http://tinyurl.com/oqtyr

And of course, there is Bill Maher's take on it.

http://tinyurl.com/jmq62

Thanks to Phil Plait, the Bad Astronomer for providing these links.

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Originally posted by marzo:
When I was a kid in the 1960's, Marvel Comics had a series of stories that took place in the 40th century and included living inhabitants on Pluto. They looked like human-shaped rock crystals and were called 'Pluvians'.
I wonder how the Pluvians feel about this decision.

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Shouldn't bother them. I'd enjoy life on Earth even if we were "dwarfed" by some alien astronomers.

On the other hand, not having consulted the Pluvians, haven't we intruded on their sovereign affairs? Is there a galactic equivalent of the Security Council? Is it any more effective than ours?

[ 27 August 2006: Message edited by: unionist ]

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Is Pluto:

A. a planet?
B. a dwarf planet?
C. a snowball in hell?
D. a sovereign solar state asymmetrically federated with the other planets?
E. a small town in Alberta?

[Choose one only. Exception: C and E may be combined.]

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E. a small town in Alberta?

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Originally posted by M. Spector:
The mighty Pluto is now Asteroid #134340.

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I just bought beachfront property on Pluto! I wanna know what's gonna happen to my property values!

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Hey Marzo, I bleed for ya, but all I can really say is that you got rooked! You let some smooth-talkin real estate con artist take you to the galactic cleaners over this.

I know it's hard to see things for yerself when looking at buying things on Pluto--I mean it ain't like there's a bus that stops there.

But it looks like the water at the beachfront you bought is frozen. Sure, it's there, but don't try goin swimmin!

My cousin got burned (or frozen) by getting conned into buying into a restaurant on Pluto that went broke.

Apparently, the food was great, the service was tops and the prices were reasonable. But there just wasn't the right atmosphere.

I know it's hard to avoid these Plutonic con artists. But there are some hints about how bad business on Pluto is just by how the name is used.

Totalitarian regimes are often called "Plutocracies," and the rich corporate backers are sometimes called "Plutarchs," not to mention that the most poisonous and Destructive substance known is called "Plutonium."

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Originally posted by Nanuq:
They do seem to be taking their time about giving 2003 UB313 a proper name and they are refusing to make it a planet. Having a planet named Xena seemed too much to hope for.

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Eris is the goddess of strife and discord.

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Eris is the goddess of strife and discord.

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