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Pluto and its biggest moon, Charon  (Source: NASA)
Pluto gets new classification: Plutoid

After being demoted from a planet to a dwarf planet by the International Astronomical Union (IAU) two years ago, the IAU has announced the term "plutoid" will be given to Pluto and similar dwarf planets.  Members of the IAU argued amongst themselves for two years, confused on how to classify dwarf stars like Pluto.  

Only dwarfs orbiting further than Neptune can be classified as a plutoid, and they must also circle the sun and be large enough to have their own gravitational field.  Pluto's permanent classification as a plutoid now means Neptune is the outermost planet in Earth's solar system; one complete orbit around the sun takes almost 165 years.

"Plutoids are celestial bodies in orbit around the sun at a distance greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighborhood around their orbit," said the IAU.

Pluto and Eris remain the only plutoids at the moment, but astronomers expect to find other small bodies that meet the qualifications to be a plutoid.

The controversy over Pluto's planet status has been strong for years, and the IAU-created plutoid classification most likely will not end the debate.  In fact, it is unlikely the debate regarding Pluto's status and what it should be classified as will never end, and defining it as a "plutoid" will only add fuel to the fire.

Many astronomers remain angry that Pluto, considered a planet for around 70 years, could have its status demoted so easily by the IAU.  Text book publishers and teachers must now begin to teach students that Pluto lost its planet status and is now a plutoid, along with describing the new classification.

The IAU has been the sole organization responsible for classifying all planetary bodies for more than a decade.

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By Jabroney on 6/13/2008 6:43:39 AM , Rating: 1
Why make things more complicated when there is no reason to? How is it going to help us any to more exactly define different types of planets? Pretty soon Neptune is going to be classified as a Neptoid and Uranus will be classified as a Uranoid, Jupiter a Jupitoid, and Mars a Moid, all because of their different colors or something like that.

RE: Pointless
By FITCamaro on 6/13/08, Rating: -1
RE: Pointless
By omnicronx on 6/13/2008 7:20:26 AM , Rating: 5
The IAU members gathered at the 2006 General Assembly agreed that a "planet" is defined as a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

Pluto fails criterion c because it has many neighbors of similar mass.

RE: Pointless
By fishbits on 6/13/08, Rating: -1
RE: Pointless
By mcnabney on 6/13/2008 9:40:57 AM , Rating: 5
Here is how it is.

They had to reclassify Pluto and drop down to 8 planets, or prepare to start adding a lot more. Eris is bigger than Pluto, so that would make ten. There are three others which are also round (but smaller than Pluto) which would follow. Unless you want the planet count to start going up towards 20 it was decided that the 'planet' definition would require the object to clear its own orbit. Pluto and the other trans-Neptunians don't.

RE: Pointless
By fishbits on 6/13/08, Rating: -1
RE: Pointless
By Machinegear on 6/13/2008 10:55:54 AM , Rating: 5
Naw... You got it all wrong.

Sure up to recently, 9 was a good number (less than 10 fingers) but today we really had to renormalize the solar system down to 8 planets. Nine planets were already pushing the limits of today's youth. The adults in charge had to think fast to stop the scientists from counting up to 20! Can you imagine the educational disaster??? Kids would have to use toes! Toes I tell you!!!

RE: Pointless
By FITCamaro on 6/13/08, Rating: 0
RE: Pointless
By Seemonkeyscanfly on 6/13/2008 2:46:07 PM , Rating: 1
Well there is no humor when talking about Pluto.
Where you are talking about Pluto the place, Pluto the dog or not Plutoid the newly developed cult for planet want to be planets, or hunks of mass, or or or fine Plutoids......

RE: Pointless
By Seemonkeyscanfly on 6/13/2008 2:54:08 PM , Rating: 2
typooo my bad... Should be whether not where.

RE: Pointless
By bodar on 6/13/2008 8:28:37 PM , Rating: 2
Pluto is serious bidness, especially on the internets.

And double-especially for Pluto the dog, since he's the only only mentally challenged character in the core Disney universe. Ducks, mice, and even other dogs talk, have jobs, go on vacations, and lead enriched, anthropomorphic lives, but not Pluto. He's just a dog. OK, that was way longer than intended. /rant

RE: Pointless
By Pythias on 6/19/2008 1:02:31 AM , Rating: 2
Kids would have to use toes! Toes I tell you!!!

I can count to 21 when I'm not wearing now.

RE: Pointless
By Seemonkeyscanfly on 6/13/2008 11:19:14 AM , Rating: 2
Great so after 6 billion years Pluto finally has a nick name. :)

Though I agree one should keep things simple when possible. However, what you are talking about sounds like far left wing politics – (Tell the people what they want to hear, keep them from the truth. The truth will just confuse them and make them unhappy). I mean so what if we have 8 or 38 planets. If in the future we find more then we add more planets to the list. Either with more or less planets, I'm not going to be able to visit any more then just one of them and see maybe 4 or 5 of them from my telescope in the backyard.
So can you explain the harm in having 20 planets? (other then just more to learn)

RE: Pointless
By masher2 on 6/13/2008 11:35:05 AM , Rating: 1
> "I'm not going to be able to...see maybe 4 or 5 of them from my telescope in the backyard."

Err, you can see five planets just with the naked eye alone...six, if you have good eyes.

RE: Pointless
By Seemonkeyscanfly on 6/13/2008 11:43:28 AM , Rating: 2
I live near a large city....the lights kill the night viewing of the sky....
Point being if there are 8 planets or 20 planets it's not going to change our lifes. So, why try to keep the number of planet at 8 or 9?

RE: Pointless
By PrinceGaz on 6/13/2008 3:22:11 PM , Rating: 5
Actually you can see six planets with the naked eye alone... seven, if you have good eyes. You seemed to forget that one of them is seen by looking down rather than up :)

RE: Pointless
By murphyslabrat on 6/14/2008 9:24:33 PM , Rating: 2
Gentlemen (and ladies, I realize some of you exist on this forum), this man needs a six.

RE: Pointless
By MRwizard on 6/15/2008 6:09:58 PM , Rating: 2

RE: Pointless
By masher2 on 6/13/2008 11:19:46 AM , Rating: 5
> "This was a pointless nerd circle jerk at the *deliberate* cost of some of the public's good will..."

It's a scientist's job to perform science, not to seek goodwill. Decisions on taxonomy should be influened by rational thought, and not public opinion.

By the way, the public is still free to continue calling Pluto a planet if they wish. They're wrong about so many other things in science, I doubt one more error will make much of a difference.

RE: Pointless
By Mojo the Monkey on 6/13/2008 3:42:47 PM , Rating: 1
Science just needs a new publicist. :)

Also, come on. That quoted comment is just hilarious to read, whether you agree or not.

RE: Pointless
By MagnumMan on 6/13/2008 10:56:38 AM , Rating: 2
Define neighborhood.

RE: Pointless
By Clauzii on 6/13/2008 6:10:41 PM , Rating: 2
Yeah, looking at the size of the universe compared to earth. Then look at the earth itself: We are all one ;)

RE: Pointless
By mezman on 6/13/2008 3:15:26 PM , Rating: 1
I fail criterion C too. :))

RE: Pointless
By Reclaimer77 on 6/13/08, Rating: -1
RE: Pointless
By jeff834 on 6/13/2008 1:48:51 PM , Rating: 5
Gosh dern right you are! Them scientists aint ever done nothin good for anybody! Why don't we just get rid of all that book lernin anyway it never did nobody no good.

People seem to think the term "scientist" means that person has to do something historically amazing or something. Scientist is just a profession like anyone else's. You don't care what farmers farm, manufacturers manufacture, or what book of the bible a preacher studies, so why should you care what scientists argue about?

The problem here is not what scientists study (which is really everything from energy concerns, astrophysics, or superconductors to penis enlargement pills), it's what is reported in the news. They discover new things in particle accelerators all the time, but you rarely hear about that stuff outside of science publications. You hear about things like what we should call Pluto because frankly its about all most people understand when it comes to science. Not all people, just most of them.

Call Pluto whatever the hell you want to call it, how often do you refer to Pluto anyway? Stop reading science stories if you aren't happy with what scientists are doing. Or better yet read a science publication and feel terrible about yourself because you haev no idea what they're talking about.

RE: Pointless
By McGuffin on 6/13/2008 6:16:30 PM , Rating: 2
I just can't understand how someone could sleep better at night knowing their 12 years of college went down the toilet as they wasted time trying to " prove " that Pluto isn't a planet.

If you don't get it, you're not supposed to. After all, it's not like knowing stuff is good for you. You just read this site for the graphics card reviews, don't you?

RE: Pointless
By Kougar on 6/13/2008 7:39:22 AM , Rating: 1
How very Venoid of you.

I suppose it is because individuals feel the need to be highly precise about terminology, however we already had perfectly acceptable terminology that could handle oddball cases like Pluto and some of our moons.

Calling it a planetoid is fine by me, is what my Astronomy professor believed, is what TNG did, and most of all leaves zero question about what the object is.

Of course, we call our natural satellite the "Moon", and call every other one a "moon" too, even when many are larger than Pluto and some larger than Mercury.

RE: Pointless
By mcnabney on 6/13/2008 10:51:00 AM , Rating: 2
Moons orbit planets. Planets, planetoids, plutoids, comets, and asteroids orbit stars.

RE: Pointless
By doctor sam adams on 6/20/2008 8:47:20 AM , Rating: 2
Moons orbit stars too. :p However, your idea is right, but what do you do in the case of a binary planet system? Both planets, and both moons of each other?

RE: Pointless
By tmouse on 6/13/2008 7:39:49 AM , Rating: 2
Interesting idea, in that case I would like to suggest if we find another celestial mass further out than Pluto in our solar system we calle Hemorrh.

from the greek for , hmmmm lets see bleeding edge, yea thats it..... ; )

RE: Pointless
By tmouse on 6/13/2008 7:42:47 AM , Rating: 3
Damm typed too fast, guess its just a joke-oid now

RE: Pointless
By Digimonkey on 6/13/2008 8:28:34 AM , Rating: 2
To late. That's what Eris is, and everyone always forgets about Ceres in the asteroid belt as well. They needed to clarify Pluto's position because of these other two objects really. If Pluto was all by it's lonesome, it probably would've stayed a planet.

RE: Pointless
By shockf1 on 6/13/08, Rating: -1
RE: Pointless
By FITCamaro on 6/13/08, Rating: -1
RE: Pointless
By marvdmartian on 6/13/2008 10:15:58 AM , Rating: 2
Yeah, but at least Pluto was named that.......and not HEMMOR , ya know?? ;)

RE: Pointless
By Kefner on 6/13/2008 11:18:53 AM , Rating: 1
No, Uranus will be a Hemroid!!

RE: Pointless
By FITCamaro on 6/13/2008 2:00:21 PM , Rating: 1

That made me laugh.

RE: Pointless
By masher2 on 6/13/2008 11:32:00 AM , Rating: 3
> " How is it going to help us any to more exactly define different types of planets?"

It already has. Pluto isn't the only plutoid at the moment: there is Eris also. Conceivably there will be many more, as we learn more about the outer reaches of the solar system.

And again, you have to remember the alternative. If the definition of a planet fits Pluto...why then it will also fit Eris and all those other soon-to-be-discovered celestial bodies. Do we really want 15 or 20 "planets" in the solar system, with the new ones increasingly divergent from what we really consider a planet to be?

RE: Pointless
By BSMonitor on 6/13/2008 11:46:04 AM , Rating: 5
Why call a dolphin a dolphin? Its a fish. It's in the water. So are sharks. Whales. People who swim. Turtles, snakes, alligators. All fish. Animals in the water are all fish.

Pluto has several major characteristics that make it unique from the other 8 planets. (aka, its orbit isn't on plane with the other 8... it's composed of a lot of ice.. it's mass is smaller than some of Jupiter's moons) Enough so that scientists have agreed that it is not a planet at all. When scientists found more objects just like it in similar orbits, they were convinced that it needed a different classification. Is it really so hard to understand?

RE: Pointless
By bmheiar on 6/13/2008 12:51:10 PM , Rating: 1
Actually dolphins & whales are aquatic mammals since they have lungs, so are required to surface to breath in air & also are warm blooded. While fish like a shark for example have gills, which extracts out the oxygen from the water. Turtles, snakes, alligators are reptiles since they have lungs but are also cold blooded. So NOT all animals who live or swim in water, are classified as fish.

RE: Pointless
By jbartabas on 6/13/2008 1:01:19 PM , Rating: 3
Actually dolphins & whales are aquatic mammals since they have lungs,[...]

Actually, I believe that it is the point he was making, i.e. not everything you find in water at some point is called fish.

RE: Pointless
By JKflipflop98 on 6/16/2008 12:46:53 AM , Rating: 2
Remember the scene where Bruce Lee is pointing at the moon, but the kid keeps looking at his finger? :)

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