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Some Demote Pluto To Non-Planet 198

Ravn0s writes "Pluto, subject of much controversy since it's discovery, has now been demoted from a planet. The Rose Center for Earth and Space, which opened last year at the American Museum of Natural History in New York is now saying that Pluto is not necessarily a planet at all but just a smallish lump of ice. Essentially, Pluto is now a largish comet. Details in this article." Other groups disagree, as the article points out.
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Some Demote Pluto To Non-Planet

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  • Oh great! Take away our planets!! Dammit, whats next?!?!
  • I always disagreed with this analysis, but back in school, they told us that Australia was both.
  • Australasia's a continent; Australia is an island.
  • Spelling errors tainted your response. No karma for you.
  • Why don't we sent a probe there, see if it gets captured by a tractor beam, and then we'll know if it's just an Imperial Ice Depot.

    (BTW what's the radius of the Death Star?)
  • The New Solar System [] (Cambridge Uni Press 1999) has a chapter on Pluto, Triton (Neptune's satellite), and Charon (Pluto's satellite). Some quotes:
    The similarities between Triton and Pluto are too close to ignore: they have comparable sizes, bulk densities, surface compositions, temperatures, and heliocentric distances (at least when Pluto is near perihelion).
    However they came to be, we suspect that Triton and Pluto have something of a shared past. On the basis of their physical similarities and their proximity to the Kuiper belt, Trion and the Pluto-Charon binary are ever-more frequently being regarded as very large members of the Kuiper belt. Pluto's status as a planet is thus challenged. However, because it was found as a result of a search for a new planet, and because it has been called one for almost 70 years, Pluto will probably retain the traditional designation for the indefinite future - at least in the minds of most of us.


  • Goofy started out life as "Dippy Dog []".

  • by pabs ( 1629 ) <> on Friday January 26, 2001 @01:59PM (#478982) Homepage
    As I'm sure others have already pointed out, this is old news. While this is mainly a political debate over semantics, there is actually some hard science behind this so-called deprication.

    Here's a quick list of the reasons I can remember off the top of my head:
    • All of the planets beyond Mars consist mostly of a large atmosphere and planet-wide ocean (thus the semi-accurate label "Gas Giants")... except Pluto. Pluto is mainly rock and ice, with little or no atmosphere. Interestingly enough, Pluto does have an atmosphere, but it freezes during Pluto's "winter" and falls to the surface.
    • All of the planets beyond Mars have a mass many times that of Earth; except Pluto. Pluto is roughly half the size of Earth's moon.
    • All of the planets in our solar system have an almost planar orbit (ie, the orbits all lie within a few degrees of the same plane). Pluto's orbit is inclined over 15 degrees.
    • Pluto's orbital radius is HUGE [] and highly erratic. About 49 times the average radius of Earth's orbit at it's peak.
    Given these facts, Pluto clearly does not belong in the same category as the 8 planets. It does, however, fit nicely with objects in the Kuiper belt []. The Kuiper belt is the collection of icy planetismals that were "kicked out" of the inner solar system instead of coalescing into planets. Their orbits are higly erratic and non-planar, and generally lie beyond the orbits of Neptune and Uranus.

    Hope this clears things up a bit...

    odds of being killed by lightning and
  • Yeah, I was trying to decide whether or not that counted. Similar to whether or not South America and North America are still the same land mass, and whether or not Cape Cod is still a cape or is now an island.
  • WHAT!!!! What fsck did she just send us!!! I used to know, but now it's just a blank!

  • When you call Pluto a comet it make me wanna vomit!! We must stop this now! These "scientists" are in the pocket of the "Big Planet" lobby that seeks to degrade and diminish the status of Pluto based on the size and icy composition.It's all president Bush's fault!! Stay out the Bushes!! Take my picture!!
  • Let's rename it "foster child".
  • I always wondered about pluto. They'd always estimated the size as small and when you look at some of our other outer planets (jupiter, neptune) they seem a bit large.

    Plus pluto is the only one with an irregular orbit. Irregular as in it kind of 'slopes' and crosses the orbit of other planets. But then again maybe other planets do the same but are so slight we just don't notice them.

    I'd bet there are more objects like pluto out there that have attained a farily regular place in our solar system but we never bothered to look, or never noticed them in the first place.

    Kind of makes you think if the earth just turned out to be one large asterioid that gathered mass and an o-zone. :)
  • Finally it greatly affects the bodies orbiting around it. For example Io is made vulcanic from Jupiters magetic influence.

    Close, it is from the immense tidal (gravitational) forces imposed by Jupiter and the other moons.


  • by okmar ( 266773 )
    ``There is no scientific insight to be gained by counting planets,'' says Neil de Grasse Tyson, director of the Hayden Planetarium, the centerpiece of the Rose Center.

    There is no signifigance in counting votes. There is no signifigance in counting days. There is no signifigance in counting people. There is no signifigance in counting processes per second. There is no signifigance in counting this person as a person.

    ``Eight or nine, the numbers don't matter.''

    4+4=8 5+4=9 8=9 Cool. I think I got it.

    You can take away all things that do not have your own life. One man's decision to call a planet any less than a planet for the world to accept as reality, is a man that should be considered liable for his credibilty and resolve his meaning with solid fact. His point is moot.

    This is cool: My dad has an autographed copy of one of Clyde Tombaugh's books. He met him at an Astronomical Society meeting. Talked to him for about an hour about all things space. Clyde deserves respect and I have a cool father.

  • Then kindly explain to me how a comet can have a moon (Charon).
  • Hemos? is that you?
  • Actually, it's losing more than 5 karma points kills your account for a day. (At least, according to Slashdot documentation. Never managed to do it before.) You have to lose all five points in one day, I think it may also be "net loss" on that day (in other words, down by 5, up by 5, your account stays active).

    It's been a while since I've gone through Slash, after I determined it wouldn't work on a website I was working on, I deleted it (small server) and haven't bothered playing around with it since.

    And I quoted your sig so you could change it - at least, that was my theory.

    (For anyone whos wondering, to lose 6 karma on a post, first get moderated up to +5, all those mod points will be lost in karma-cap limbo; then have someone point you out as a troll, and get moderated down to -1. Presto, net loss of 6 karma points. Which is really stupid, since posting at Score: 2 should only allow 3 points of karma to be lost.)

  • that one day orbiting celestial bodies will not be labeled and judged base on the materials they are made of. I see a day of gasses playing with solids and oh nevermind, why couldn't this article be posted a week ago ;-)
  • Really? I don't think that the exact shape of Ceres is completely known. Still, a quick google at the web indicates that Ceres is irregularly shaped, which says it is an asteroid.
  • by TrevorB ( 57780 ) on Friday January 26, 2001 @01:05PM (#478995) Homepage
    Read the fg article! This is about one museum in New York that decided to label Pluto as a non-planet in a single display. This isn't the gathering of an astronomical society declaring Pluto a non-planet!

    Not that Pluto is a *real* planet anyway, but that's beside the point. :)
  • There are also rocks on pluto. If you think about it, what are the rest of the planets? Hunks of rock and ice. What should make pluto any different. And pluto has a diameter of 1375 miles (2200 km), not 2500 miles.
  • ...all I can say is, there are going to be some pissed off astrologers if this thing ends up being popularly reognized. Imagine having to explain to someone, "Okay, so you weren't exactly born under a planet, but..."

  • by jonfromspace ( 179394 ) <> on Friday January 26, 2001 @01:07PM (#478998)
    I bet the Ice People living near the core of pluto are gonna be pissed...

    I bet this is Hemos's doing... 'cause we all know he is an Alien []. After that Optical SETI crap [], we should have expected this.
  • None of the planets orbit on the same plane, pluto's is just more uneven.
  • by DeadVulcan ( 182139 ) <> on Friday January 26, 2001 @01:08PM (#479000)

    The Rose Center says there is no universal definition of a planet...

    Then make one! We shouldn't be debating whether Pluto is a planet, we should be debating what the definition of a planet should be. Then, Pluto will come out in the wash.

    ...a 1999 proposal to list Pluto as both a planet and a member of the Kuiper Belt was abandoned after it drew strong opposition from astronomers who did not want to diminish Pluto's status.

    I can't believe people are getting territorial about Pluto.

    Why is this news?


  • I could say that Pluto is just a 2,500 mile-wide hunk of ice.

    You could say that, but you'd be wrong. It's only 1,413 miles wide, smaller than the Moon, as you'd have discovered had you read the article. This has a lot to do with why the Rose Center demoted it.

    I'd say a center devoted to astronomical education has a whole lot more authority to decide what is and is not a planet than the general public. Pluto has the composition of a comet and shares an orbit with 70 other objects that are definitely comets. Ergo it's a comet, albeit a large one.

  • I'm quite interested in this, and I'm just a lowly hs student.

  • ... is that Pluto is the only "planet" discovered by an American, one Clyde Tombaugh if memory serves.
  • NASA is not an authoritative astronomical authority anymore than Wright Air Force Base.
  • NASA is not an authoritative astronomical authority anymore than Wright Air Force Base.
  • How many roads must a Man walk down before you can call him a Man?
  • >Sure, but there are a bunch of asteriods (the
    >largest being Ceres which has a diameter of 933km)
    >which also meet that criteria.

    AFAIK Ceres has never been seen clearly enough to determine whether it is a spheroidal shape or not. In fact it transitted a star a while ago and the results indicated that it was surprisingly irregular. But I wouldn't exactly cry if Ceres counted as a planet anyway.

    I'm not aware of any spheroidal asteroid that is smaller than Ceres either. If you have proof to the contrary, I would like to see it.

    As for all your other points about pluto- so what. Every single body in the solar system appears to be completely different to every other.
  • ACK!

    everyone will need to make up new acronyms for the listing the planets!

  • How will kids learn the order of the planets now?

    My Very Energetic Mom Just Sold Us Nothing?
  • How many roads must a Man walk down before you can call him a Man?

    Easy, 42. Can I have some cheese now? *squeak* ;)

  • by jamiemccarthy ( 4847 ) on Friday January 26, 2001 @02:19PM (#479018) Homepage Journal

    He can orbit the sun, he can look like a moon
    He can leave the ecliptic from April to June
    He'll be just a faint smudge, magnitude twenty-three
    He hides in the sky, but he's always a planet to me

    Ohhh...a potato-shaped ball...
    He can drift where he wants
    He's a relic of time
    Ohhh...if he's made of pure ice
    Or of vapor and dust
    It's the same to my mind

    If he zooms in near us, would he show us a tail?
    Was the Kuiper Belt once the great home whence he sailed?
    And if he gets demoted, who'll be next, Mercury?
    And the most he can do is cast shadows, it's true
    But he's always a planet to me

    Jamie McCarthy

  • by Anonymous Coward
    I'm not sure why anyone really cares. Regardless of pluto's official status, it has a given mass, and an orbital pattern which was discovered decades ago. The only people who care are the same sort of people who really think that there's a difference between addressing someone as a "maid" or a "houskeeper"...
  • by Adam Wiggins ( 349 ) on Friday January 26, 2001 @02:22PM (#479020) Homepage
    ...and because of that, I think I will have to applaud their actions.

    Kids get things drilled into their heads, like how many planets there are. Instead they should be taught in a way that's a little less discreet such that they come to an earlier realization that the universe isn't black and white, any more than life is.

    A friend of mine (who grew up and went to school in Japan) thought that there was only one moon, "The Moon." Again, I think this is reflective of a strict regimine of memorizing facts rather than exploring the wonders that our universe has to offer.
  • My Very Patient Mother Just Served Us Nine ______

    Served us nine what?!? We'll starve without the pizzas! We need Pluto to avoid world-wide starvation!
  • by DeadVulcan ( 182139 ) <> on Friday January 26, 2001 @01:13PM (#479025)

    Okay, I'm replying to my own post, but I just thought of a better way to express myself.

    When does an island become a continent?

    When does a town become a city?

    When does winter become spring?


  • AFAIK Ceres has never been seen clearly enough to determine whether it is a spheroidal shape or not. In fact it transitted a star a while ago and the results indicated that it was surprisingly irregular. But I wouldn't exactly cry if Ceres counted as a planet anyway.
    Ceres was discovered well before Pluto, and was consider to be a planet for about a year. A (very low quality) image of Ceres is available here [].
    I'm not aware of any spheroidal asteroid that is smaller than Ceres either. If you have proof to the contrary, I would like to see it.
    Searching for "spherical asteroid" on Google lead me to this [] article which states that Vesta is "nearly spherical". Pallas is believed to be spherical (see here []). This [] article says there that "at least a half-dozen main-belt asteroids are large, spherical objects that would also satisfy definitions of "major planethood" if sphericity is the criterion." That last article is a pretty good coverage of the debate over Pluto's status.
    As for all your other points about pluto- so what. Every single body in the solar system appears to be completely different to every other.
    None of the other major planets have anywhere near the "weirdness" of Pluto. About the only thing Pluto has in common with the other major planets is that it orbits the sun. The others are relativly similar. So why do you think Pluto should be considered a major planet?
  • All astronomers really know that planets are planets because they have Sailor Senshi. Setsuna Meiou is Sailor Pluto, therefore Pluto is a Planet.


    I think a few astronomers are going to be listening to a "Dead Scream" in the near future.
  • Since these are standards we're talking about, they are facts by virtue of a formalised agreement in an international group of peers in their fields of study.

    Countries get together and form an organisation which is assigned the authority for naming and measurement standards within a given field. By creating a formalised common language, they facilitate the unambiguous flow of information.

    Using a completely different system causes a lot of problems, and isn't viable. Tweaking the system arbitrarily is nothing more than an ego-trip; a way of saying, "I'm important enough to follow my OWN rules!" while doing nothing of the sort. Or alternatively, it could be plain ignorance.

  • Weirdness? Uranus has an angle of dip more than 90 degrees! It spins the wrong way! You could go a long way to be weirder than that. Nobody has much clue how that could happen. Perturbing an orbit out of the ecliptic is trivial in comparison.

    Ok, so Pluto's orbit is a bit skewed to the ecliptic. I can live with that. So it is tidally locked to its moon. Even the earths moon is tidally locked, and the earth will be locked to the moon as well eventually if nothing happens to stop it. These are not exactly hugely unusual.
  • by speck ( 29023 ) on Friday January 26, 2001 @02:28PM (#479032) the obvious fact that demoting Pluto to a mere Kuiper Belt object runs the grave risk of offending its namesake, the dread Lord of the Underworld. I have yet to see any respectable scientist propose the obvious solution to this problem: to ameliorate Pluto, several fattened heifers should be slaughered in sacrifice on the steps of the Rose Center []. I'm shocked, shocked that these scientists would risk angering the god; the last time someone (namely, Persephone []) did so, Demeter plunged the Earth into famine, and ulimately the seasons were split in two.
  • Old Dispute, old news.

    This argument has been going on forever. What makes a planet, a planet? Who cares. Even minor-planets are planets.

  • I can see it now...

    Subject: FP
    Comment: RTFA!
  • To my mind a planet is something that is made round by its own gravity, and is in orbit around a star.

    Clearly under that definition Pluto counts as a planet. Pluto even has a moon called Charon.

    Sure, but there are a bunch of asteriods (the largest being Ceres which has a diameter of 933km) which also meet that criteria.

    There are a whole bunch of reasons to not consider Pluto to be a planet:

    • Pluto has a composition unlike any other planet. It most closely resembles Triton (a moon of Neptune).
    • Pluto has an orbit which is unlike any other planet. It's orbit is inclined 17 degrees, and is high eccentric - it is sometimes closer to the Sun than Neptune. It's orbit is similar to at least 70 other Kuiper belt objects.
    • It's "moon", Charon, is in a synchronous orbit (it's position is fixed relative to Pluto's surface). No (other) planet in the solar system has a natural satelitte in synchronous orbit.
    • Pluto is far smaller than any other planet. It is half the size of Mercury and only two-thirds the size of our Moon. It is likely that many other Kuiper belt objects will be of similar size.
    • Pluto is also very light in terms of mass. Current estimates put it's mass at around 1/500 of Earth's.
    The fact that Pluto is made of ice is irrelevant- Jupiter is made of gas. Does that mean Jupiter isn't a planet?
    Jupiter has a metallic core (as do all the other gas giants). In my view the two most damning factors are the orbit and the size of Pluto. Composition is of lesser concern. Note that we don't know for sure that Pluto doesn't have a rock or metal core, it's density is higher than that of the ices that it is thought to be primarily composed of (nitrogen, methane, and carbon monoxide).

    For reference, here [] is the 2 year old CNN article about how the International Astronomical Union was/is considering reclassifying Pluto as a minor planet (like many asteriods). They decided against it. This [] is a really good article from Sky and Telescope covering the debate.

  • This is because everyone knows that they just want to demote Pluto because the hate Clyde [] and that people who hate Clyde also hate Tesla [] and that people who hate Tesla are evil and should die. (Note the above is a joke except the part about people who hate Tesla needing to die.) But my understanding is that many astronomers *really* like Clyde and therefore really like Pluto.
  • Jupiter is a gas giant and as far as we know we can not land on it (Unless it really does have a solid core). So by your reasoning Jupiter is not a planet.
  • Pluto is NOT mostly ice : it has the density of TWICE water (and ice is less dense than water). It has a rocky crust! It has an atmosphere! It has a moon! What more can you ask?!

    This Tyson fella should be brought up to the next American Astronomical Society (AAS) meeting and asked to repent.

    Besides, nobody is going to listen him anyway.
  • Pluto has all the characteristics of a Kupier belt object. Why not call it a Kupier belt object?
  • The first idea that popped into my head was that a planet is anything that's hard for me to jump off of.

    Do any moons have moons?

    Some asteriods have moons. Some of the asteriods had enough gravity to become spherical during formation. Also some astronomers expect that there are many Pluto sized objects in the Kuiper belt, so that definition might prove controversial.
  • I think this is a good thing. I was always annoyed seeing perfect good astological predictions messed up by the addition of all these new planets. Seven planets is nice and symetrical.

    If Isaac Newton didn't need Pluto for his astrology, we shouldn't need it for ours.

  • The Sinclair ZX-80 has been demoted to a programmable calculator and is no longer considered a computer.
  • Ummmm...last time I checked, Neptune was further out than Uranus...
  • The way I learned it was My Very Educated Mother Just Showed Us Nine Planets. Where I come from, we call the third planet "Earth".

    You must be from that 9th planet out there. I'm glad to hear you call us Pluto. What do you call yourself?

    PS: Sorry about the demotion, mate

  • And Jupiter is just one big mass of gas.
  • It could be argued that Jupiter isn't a "planet" at all but is really a failed star. It's rotation is too fast given it's size (8.8 hours). It emits more than twice the energy it should if it was just reflecting light. And it has no visible surface. Finally it greatly affects the bodies orbiting around it. For example Io is made vulcanic from Jupiters magetic influence.

    Mercury has not atmosphere and should be reclassified as a moon....

    See how it starts? Now make your own argument debunking the other orbiting gas balls and big rocks.
  • I've got a question. Is there a reason why all of our planets orbit on basically the same plane? Why would it matter with a spherical body at the center?

    It's because the spherical body is spinning, IIRC. It's also the same reason why moons (and ring systems) tend to be in equitorial orbits.
  • The Plutonians are sick and tired of being ignored.

    As their "element" is plutonium maybe ignoring them is not such a good idea...
  • A few years ago when my younger sister was doing some of that same stuff i saw that they had split that into two seperate food groups, one for fruit and one for vegatables.

    Good idea make "food groups" inconsistent with botanical classification, where "fruits" are a subset of "vegatables".
    Added to which many things cxalled "vegatables" are actually "fruits".
  • The similarities between Triton and Pluto are too close to ignore: they have comparable sizes, bulk densities, surface compositions, temperatures, and heliocentric distances (at least when Pluto is near perihelion).So did Nepture loose a moon or did it capture a planet...
  • The serious astrologers (the ones who, unless they're math wonks, need a computer to draw your chart) have been using all the new planets since not long after their discoveries. This is something I found interesting back when I was hanging out in New Age circles.

    How, you might wonder, do these guys determine what the influence of, say, Uranus is on your chart? When the planet is discovered they cast charts of people and events including the newly discovered object, and work those charts backward to see if there are any consistent patterns of influence. They also take hints from the object's properties (color, distance, size, etc.) on the assumption that things are conveniently labelled for us by a consistent Nature (the "law of signatures").

    Anyway, Pluto or no Pluto, now that the Age of Pisces is definitely over we can finally look forward to the demise of Christianity and its replacement with something more, well, Aquarian :-)

  • At least one asteroid [] does. But even so, Charon [] is awfully big for a moon. No other planet has a moon that's so large relative to it, and the two bodies are more or less in a position of orbiting each other. In any event, I don't see how any of this disqualifies Pluto from comet-hood.
  • DUH!

    My karma's bigger than yours!
  • Comets have tails. Pluto doesn't have a tail.

    Is this serious? Comets only have tails as they approach the Sun as material is evaporated from their surfaces by the heat and energized by the solar wind. Pluto is far too distant from the Sun for this to happen.

    Also, it's alone

    Read the article, will you? It shares it's orbit with about 70 other objects that we know about, and crosses orbits with many other objects in the Kuiper belt.

    and has a definable orbit.

    So do most other comets. So what?

  • To my mind a planet is something that is made round by its own gravity, and is in orbit around a star.

    Clearly under that definition Pluto counts as a planet. Pluto even has a moon called Charon.

    The fact that Pluto is made of ice is irrelevant- Jupiter is made of gas. Does that mean Jupiter isn't a planet?

    Anyway check out: for TNOs and other good stuff.
  • That's the surface. Water, solid or liquid, comprises only a very small portion of the total composition of the Earth.
  • Pluto's out there thinking to itself "Who do those bastards think they are? I'll show you a planet, beeyotch!" and starts hurling comets from the Oort cloud. Damn scientists.
  • Who says they are mutually exclusive?
  • the center of mass is actually outside of pluto
  • I know I was taught Europe was it's ownn continent. And that some people wanted India to be it's own continent.

    But why is Europe considered a continent? India is at least on a different techtonic plate than asia. I don't beleive that's the case with Europe and Asia.

    Dare I speculate that the reason Europe is considered it's own continent is due to the history of our planet's continents? Please, someone tell me there's a better reason.
  • we also know it's density, due to the orbital period of it and it's "moon". Based on its density (and it's lack of a significant atmosphere) there can't be much rock.
  • I'm not bashing Pluto, but I really don't mind having eight planets. They argue how they should define a planet, whether by size or orbit type.

    I just think we should define a planet as an object of a certain mass and diameter (Pluto's size or larger) that orbits on a similar plane as the other more noticable planets.

    Instead of it's wierd tilted orbit.

    Just my opinion.
    ...and I'm not sure we should trust this Kyle Sagan either.
  • the "discrepancies" turned out to be errors in the measurements. Of course I can't say there isn't something so dark and far away that it hasn't been discovered, but there is no longer a problem that "requires" another massive body in the solar system
  • I think this is just the European Union attempting to flex their intellectual muscle.

    Pluto is unique in the fact that it was the only planet not discovered and/or named by a European.

    The Greeks named the first 5 extraterrestrial planets, and Europeans named Uranus and Neptune. But Pluto was discovered by Clyde Tombaugh in Lowell Observatory in Flagstaff, Arizona, in 1930.
    *Carlos: Exit Stage Right*

    "Geeks, Where would you be without them?"

  • It's beleived to be due to the planets forming from a disk of gas and dust. You ask why was the disk not a sphere? Well, in a protoplanetary disk the gas provides friction which tends to cause things to move is smooth coplanar, low eccentricity orbits. A small ammount of initial angular momentum (presumablely random) became more significant as the solar systems contracted to form the star and broke the symetry
  • of the Disney company. It's also a God.

    While this may all be old news, we need to understand that the International Astronomy Society gets to decide these things, and that is not a scientific process, but a political process disguised as science.

    Just as Pluto is a Dog disguised as a Trademark. And Dog spelled backwards is ...

  • While the abovecomment is funny, it does illustrate a serious point - we don't have exact, unambigious definitions of "planet", and there are objects at both ends of the size spectrum that are straining our definition (Pluto at one end, some of the supermassive gas giants discovered around some neighbouring stars at the other).

    So, to paraphrase the Walrus, planet means exactly what we choose it to mean, no more and no less.

  • If you think about it, what are the rest of the planets? Hunks of rock and ice.

    The terrestrial planets are rock, with small amounts of ice occurring only on the surface of two of them. Ice isn't a major component of their composition. The gas giants may have small rocky cores, but they're mostly hydrogen and other gases. If Pluto is a planet, its composition is entirely unique relative to the others.

  • And that my friends, IS the point ... Which is all the more reason this topic doesn't belong on Slashdot TWICE!

    My karma's bigger than yours!
  • There will soon be a resolution to this raging controversy. Recent discoveries with the large infrared telescopes that have come on line in the past decade are beginning to show that stellar and planetary objects have a continuous range of sizes and masses, from the largest O-type supergiant stars, to sun-like G-type stars, to brown dwarfs, hot Jupiters and rouge planets travelling freely through space. Where ever we're able to look, we're finding objects in space at all points on the size curve.

    What looks to be shaping up is this:

    • Stellar objects are those that have condensed from galactic gas clouds. This includes ordinary stars, brown dwarfs, and possibly the new rogue planets that have been uncovered far from any parent star
    • Planetary objects are those that have condensed from the protoplanetary disk surrounding new stellar objects in the early stages of formation
    Under these definitions, stars and brown dwarfs are stellar objects (or just "stars"). So are the rogue planets that have been recently found, if it turns out that they condensed directly from interstellar gas and dust. Hot, massive Jupiters, Pluto, other comets and asteroids are planetary objects, and so are their moons, if any (you can call these "planets").

    The discovery of the rogue planets turns out to be a recent key to this puzzle. It appears they formed directly from a collapsing interstellar dust/gas cloud, rather than in a protoplanetary disk surrounding a newly formed star. It appears that objects of any size can be formed this way, not just stars and brown dwarfs. To the limits of our ability to see, we are finding smaller and smaller objects that are planet-sized, even Moon-sized, but formed in a completely different environment. We can only see them shortly after they form, while they are still radiating with the heat of collapse.

    So size, mass and orbit may turn out to be not so useful in classifying objects as stars or planets. The process by which they formed looks like it will turn out to be the more meaningful way to classify them.

  • Similarly, Europe? Eurasia may be a continent but Europe is a social abstraction.


  • No. Australia is a continent. The definition of a continent is fairly arbitrary, but basically it means a large, continous mass of land. According to the Encyclopaedia Britannica the continents are North America, South America, Africa, Antartica, Australia, Asia, and Europe. Asia and Europe are sometimes combined into the single continent Eurasia. While Australia is often considered an island, it is four times larger than the next biggest (non-continental) island, Greenland.
  • Since /. loves conspiracey theories, I'll share one...

    We've sent probes to every planet in the solar system, except pluto. Ah ha! Clearly, we need to send a probe to the only planet we haven't explored yet. This is exactly the argument some people (including professional astronomers, NASA policy folks, etc.) use in trying to justify a proposed mission that still hasn't been funded, the Pluto-Kuiper Express. If pluto is demoted to a Kuiper belt object, the "necessity" of that mission (which some people have already spent years of their career on) is gone. Hence the ridiculous tenacity of some astronomers and even the IAU to insisting that Pluto is a planet.

    Personally, I think sending a space probe to a couple of Kuiper belt objects is a worthy goal in and of itself. I have no objections if one of them is Pluto/Charon. Indeed there is some urgency since it's getting harder/more expensive to do such a mission because Pluto is receding from Earth in it's very long period orbit.

    In any case, I think as soon as the mission is launched (or maybe once it's finished visiting Pluto), you'll find most astronomers who previously resisted the idea will be much more willing to admit it makes more sense to call it a kuiper belt object.

  • Pluto a dog????


    Planet Pluto is the coolest and most far out planet in the Solar System. Pluto was known as the god of the dead in Roman mythology. The Romans sometimes called him Dis Pater or Orcus, and the Greeks sometimes called him Pluton. Pluto was also known as Hades, the Greek god of the dead. The Romans borrowed almost all the myths and legends about Pluto and his affiliation the the underworld that he ruled from the Greeks.

  • Although I see you're where you're coming from...

    I beleive it would make more sense to say that desparately clinging to the idea that Pluto fits in the category of planets better than the category of Kuiper Belt objects tends to be associated with people who have an interest in the Pluto-Kuiper Express happening.

    I would place the odds at better than 1000:1 that if Pluto were discovered today (now that we know of hundreds of similar objects), it would be considered a Kuiper belt object. It's status as a planet is only an artifact of history.
  • Australia is no longer a continent, it has instead been demoted to an island!

    My karma's bigger than yours!
  • l

    If pluto didn't have a special symbol, and orbit drawn for it, could you pick out Pluto as different from other Kuiper belt objects?

  • So will Eros, the asteroid that the NASA probe NEAR/Shoemaker is about to land on (I think Feb 12) become a planet?
  • (now to see if the moderators are sluts or virgins....)
  • I don't hear people complaining that Ceres isn't a (minor) planet, so why pick on Pluto?
    That's because Ceres IS a Minor Planet, infact it is the first object in the Minor Planet Catalogue. What we are actually debating here is whether Pluto should be considered a Major Planet. One of the proposals voiced in 1999 about this was to give Pluto the number 10,000 in the Minor Planet Catalogue.
  • Your definition probably won't fly, as there are a number of asteroids (Ceres comes to mind) that are large enough to be drawn into a spheroid by their own self-gravity.

  • To be fair, we don't know exactly what Pluto is composed of; we just know its surface composition on the basis of spectroscopic data.

    Not that anyone is asking me -- I'm a sysadmin, not an astronomer -- but if it orbits the sun and it's large enough for its gravity to mash it into a spheroid, it ought to be called a planet. With the same amount of hair-splitting that's being applied to Pluto, you could argue that Jupiter isn't a planet at all but a pre-stellar mass instead.

    In the end, it is mostly a debate over semantics and a strangely snotty one, considering how little it matters what we call Pluto. The unfolding story of its origin, like that of other solar system objects, is much more interesting (and substantial) than this petty labelling debate. Let's do something useful instead and urge Congress to fund a Pluto/Kuiper belt survey mission and at least generate some interesting data to argue about. Otherwise, this is just an exercise in cartographic conventions.


  • I mean, who are these losers? How many AUs is Neil Tyson's head up his ass?

    OK, so I'm not being polite. I'm sick and fucking tired of people (especially educators and scientists) who should know better declaring whatever they damned well feel like, regardless of the facts.

    Here then are some facts that deserve to be spread and repeated, until they replace the incorrect versions.

    FACT: Pluto is a planet. The INTERNATIONAL Astronomical Union (not some fucking museum in the US) says so.

    FACT: The 13th element on the periodic table is aluminium, not aluminum. IUPAC has confirmed it time and time again, regardless of what the bloody ACS says.

    FACT: A meter is a device. A metre is a unit of measure.

    And so on.


  • by Colz Grigor ( 126123 ) on Friday January 26, 2001 @01:03PM (#479169) Homepage
    Pluto No Longer a Planet-- Disney Company Proud of Efforts

    Kissimmee, Florida-- After many months of exercising and maintaining a healthy diet, Pluto, the loveable dog of Mickey Mouse, has finally met his goal weight. "He struggled with it for a while, at first," says his proud and famous owner, "but cutting his intake of doggie treats has brought him back down to an acceptable weight."
    "We look forward to seeing him act in movies again," Mickey's girlfriend, Minnie, added. And so do we all...

    ::Colz Grigor

  • When i was younger (im still in my early 20s) there were only 4 food groups, now there are 5. There were 9 planets, now only 8. How can i get the authority to split food groups or demote planets?

They are called computers simply because computation is the only significant job that has so far been given to them.