Why would the International Astronomical Union now represent Pluto as a dwarf planet?
806256
The International Astronomical Union decided that Pluto was no longer a planet. The reason is that while Pluto is round, orbits the sun, and has three moons, it has not cleared (via gravity) its own orbit of debris.  Instead, they decided to classify it as a "dwarf planet".\n\nSee the details below.\n\nRESOLUTION 5A\nThe IAU therefore resolves that "planets" and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:\n\n(1) A "planet" [footnote 1] is 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.\n\n(2) A "dwarf planet" is 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 [footnote 2] , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.\n\n(3) All other objects [footnote 3] except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".\n\n\nFootnote 1: The eight "planets" are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.\n\nFootnote 2: An IAU process will be established to assign borderline objects into either dwarf planet and other categories.\n\nFootnote 3: These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.\n\nRESOLUTION 6A\nThe IAU further resolves:\n\nPluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.
389936
Nope.  That's my professional (astronomer) opinon.  Here is why:\n\nPluto is a member of a large collection of similar sized objects that orbit the sun in the same region as it.  This is the same situation that Ceres, the largest asteroid is in.  Pluto was simply the first of these icy bodies to be found, we have since found almost 1000 other objects that share orbital space with Pluto.  Many of them are almost the same sice as it, and one (2003 UB313) is in fact larger than Pluto.\n\nNo good defination of planet exists that allows for pluto to be a planet without admitting about 10-100 other objects in as planets as well, unless you simple state that Pluto is a planet in an ad hoc manner.\n\nThe definition that I generally use in my work is that a planet is an object that has cleared it's orbital space of all other small bodies.  All of the main 8 planets satisfy the criteria.  Pluto, 2003 UB313, Ceres and other small bodies do not.
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All orbits are elliptical (note that circles are subsets of ellipses.)  Exactly how Pluto go to be where it is (and where also includes its coordinates in a velocity space, in addition to xyz space) is not known.  One interesting thing about it is that it is in a resonance with Neptunes orbit, so that whenever it is close to Neptunes orbit, Neptune is on the other side of the sun. Neptune's mass can't perturb Pluto.  In other words, Pluto is in a special orbit that is stable. \n\nI doubt it had its origin as a moon of Neptune, or else it likely would have been flung into a very radical orbit by an encouter with that planet. More likely it is one of MANY objects that found itself orbiting in similar orbits; all the others have long ago been removed from the picture by Neptune encounters.
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Depends on how long ago you were in school -- Pluto is so far away that for many years we thought it was larger than it has turned out to, in fact, be.\n\nThe most recent value I have for the diameter of the two planets is:\nMercury = 4879.4 km\nPluto = 2302 km\n\nThen, of course, there's the debate about whether or not Pluto is even truly a planet . . .
352951
Probably because, as many astronomers think, Pluto isn't really a true planet, but a huge asteroid that once had a very erratic orbit that has gradually stabilized over time.
1101184
2003UB313. Although its still not officially a "planet". Neither is Pluto for that matter. From what I know UB313 is an educated assumption made because of a variance in  Pluto's orbit. In other words something is causing Pluto to "move" a certain way along its orbit. It would definately take  a large celestial object to cause this to happen but Im not sure if it has definately been determined that its a planet
2903
I quote : "Two small moons have been discovered orbiting Pluto, bringing the planet's retinue of known satellites to three and leaving scientist to wonder how it could be. ...The moons are catalogued as S/2005 P1 and S/2005 P2 for now. Once they are confirmed, the discoverers will suggest names, to be approved by the International Astronomical Union."\n\nFrom: http://www.space.com/scienceastronomy/051031_pluto_moons.html
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There are actually several "planet like" objects beyond Pluto in an area called the Kuiper belt that contains thousands of objects that circle the sun.\n\nAt present none of them have been officially recognized as new planets. \nThe discovery of these new planet size objects including  2003 UB313 (nicknamed XENA), Sedna(in 2004) and Quaoar(in 2002 by the same team) have triggered a re-evaluation of the necessary criteria to call something a planet.\n\nIt is likely that this team at Caltech will  discover other objects to be added to the list of potential "planets" in our solar system.\n\n2003 UB313(nicknamed XENA unofficially) is larger than Pluto which leaves officials in a bit of dilemna.  How can they recognize Pluto as a planet and not this object?
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It's current name is 2003 UB313.  It is larger than Pluto.\n\nBut is not yet officially recognized as a 'planet'.\n\nThat may change later this year as the International Astronomical Union (IAU) firms up the definition of a planet.\n\nAt that point, it will probably be renamed.  The discoverers of the object have submitted confidential names to the IAU.  Some people call it Xena or Lila, but these are not official names, and are not among the names submitted to the IAU.  \n\nIt is not 'Planet X' ... this is a generic name for a theoretical large planet not yet discovered.  (Pluto was once thought to be 'Planet X', but it is too small.)  The Planet X theory has been disproven.\n\nSedna is a smaller object (smaller than Pluto), and may also be reclassified as a planet ... but I don't think it's likely.\n\nOne thing is for sure though ... Pluto will not lose its classification as a planet ... astronomers are sentimental too.
973992
Something less than 400 members of the 10,000 member IAU voted under a veil of assumed authority to downgrade Pluto's status as a planet after they rewrote the rule book. Most of the new criteria they established that must be met in order for an object to be considered a planet is met by Pluto. It orbits a star, it has a moon, and it is generally spherical in shape. The disqualifying new rule was that Pluto has not cleared its orbital path around the sun and there are other objects sharing the same orbit. This would mean that if another object enters or is found to exist in the same orbital path of the Earth, the Earth would not be a planet. The IAU also failed to take into consideration as to whether or not Pluto is in the process of clearing its orbital path and just needs a few billion more years.
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Actually, the people who found it honestly want to have it called Xena.\n\nOn July 29, 2005, a Trans-Neptunian object called 2003 UB313 was announced, which on the basis of its magnitude and simple albedo considerations is assumed to be larger than Pluto. This caused its discoverers to call it the "10th planet" of the solar system, although there is no consensus yet on whether to call it a planet, and others consider the new discovery to be the strongest argument yet for demoting Pluto to the status of a minor planet.\n\nBut until then, it's being refered to as Planet X.
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There are alot of objects that exist beyond Pluto. Yet, at this point none of these is really large enough to be considered a planet. Check the source link for more info.
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no. The majority of scientists define the main requirement of a planet to be it's gravatational domination of it's surroundings; something pluto and 2003 UB313 do not do; in fact, both Pluto and 2003 UB313 aren't even the size of earth's moon. The main reason there is even controversy on this topic is because Americans were the ones who discovered Puto and the other icy rock and wanted to have some kind of historical placement in the field of Astronomy.
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To answer your second question first (I'm just an ornery cuss), Pluto is still a member of the Solar System. It's no longer considered a planet, though. It is now called a dwarf planet because of its size and extremely anomalous orbit (so look it up already).Just like the moon. asteroids, etc. it is still part of the Solar System.\n\nAs to the 1st part of your question-------Usually, as long as Mickey gives him table scraps instead of that crap from the can.Woof!Woof!
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http://en.wikipedia.org/wiki/Pluto\n\non 24 august 2006, the international astronomical union reclassified pluto.\n\npluto does orbit the sun, is ball-shaped and is not a satellite, but it does not have an isolated orbit (a bunch of other similar bodies have similar orbits.) so it is not a planet.\n\ni have been waiting for this since i was about ten when i learned that pluto didn't fit the pattern set by the major bodies in the solar system so it was an anomaly. it just felt "out of place". now that astronomers have found hundreds of other bodies with similar orbits, classifying "134340 pluto" as a planet is even more irrational. i feel somewhat satisfied, but i don't know how long this will drag on tho. many planetary astronomers are satisfied that the definition is rigorous enuf. i can accept that the definition is flawed, but i can not accept that "134340 pluto" is a planet.\n\nthis was the right thing to do, believe me. this does not change anything about pluto or the solar system. this just corrects the mistake of classifying pluto as a planet initially.\n\nthis same thing happened has happened before.  in 1800, an astronomer found a body orbiting between the orbits of mars and jupiter and thought it was a planet.  astronomers finally stopped classifying them as planets after they found several other bodies with similar orbits, and no one thinks ceres, pallas, juno, and vesta are planets today.\n\nmany astronomers consider pluto and charon to be a binary system, but two small bodies orbit that system. they are called nix and hydra.\n\nincidentally, "134340 pluto" was never a moon of neptune. neptune did capture triton. this is why triton has a retrograde orbit
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The tenth planet is like really great, thanks for asking.  He spins around and around and makes one revolution around the sun about once every several thousand thousand years.  Therefore you might call this tenth planet (he doesn't mind) a chunk of ice, and not really planet-like at all.  But wait, you're saying, Pluto is a chunk of ice and also a planet!  Well, Pluto actually (he's telling me now) doesn't even consider himself a planet, as he's really just a large ice-chunk in the Kuiper Belt.  The tenth planet (we'll call him "Frank", that's what he prefers) is a little peeved that Pluto gets a thousand-brother belt to wear and all he's got is the occasional through-comet.  We can't help you, Frank, I'm sorry.  We're like, a billion miles away.
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Pluto - 1930.\n\nPluto is still considered a planet and all the objects that Mike Brown et.al. have been finding (Sedna, 2003UB313, etc.) have not been granted planetary status, no matter how often Mike Brown says that 2003UB313 is a planet, quite simply it is not.\n\nThe IAU's Division of Planetary Science is currently working on the whole planet issue, and we are supposed to have some sort of resolution to this issue by august of this year.  Right now it seems that we are leaning to either strip Pluto of its planetary status, through making an actually definition of the word "planet," or to make Pluto the arbitrary cut-off line.  This would mean that 2003UB313 would become the 10th planet, but Sedna (being smaller than Pluto) would not.\n\nAs of right now there is no official motion in place to remove planetary status from pluto, although it may loose it through the adoption of a new definition of what a planet is.\n\nAlso, no matter how catchy the name sounds, or how often the BBC calls it that, the official name of 2003UB313 will not be "Xena," that was simply Brown's code name for that object.