back to article YOU! DEGRASSE! It's time to make Pluto a proper planet again, says NASA boffin

Those who feel that Pluto has always been a planet and jolly well ought to be one again have received a boost - this time from a top NASA boffin, albeit a slightly biased one. "It's very hard not to call an object with this level of complexity in its geology, and such complex seasons, a planet," said Alan Stern, New Horizons' …

  1. John Savard Silver badge

    Wishing and Hoping

    For sentimental reasons, I would very much like Pluto to be a planet, pure and simple, once again. However, that would mean that Eris would have to join it as a new planet in our Solar System.

    And that's the problem, because there could be many other planets in the Kuiper Belt of comparable size. For a while, Ceres, Pallas, Juno, and Vesta were accepted as planets - but then it was clear this would be untenable, as the extent of the asteroid belt began to emerge. It appears that the same thing has repeated itself when it comes to KBOs.

    Whether or not we like it, I think the IAU's decision makes sense and was the only one possible.

    1. JeffyPoooh


      "If Neptune had 'cleared' its orbital zone, then Pluto wouldn't be there."

      .: The IAU are idiots.


      Note. I don't really care if Pluto is a planet or a dwarf planet. But it's important that bogus logic be ridiculed at every opportunity. The IAU bungled this one, and deserve no mercy.

    2. skerns0301

      Re: Wishing and Hoping

      The fact that Pluto has a techtonily active crust (Mercury and Mars don't) should rank Pluto above them on the planet list--the simple fact is Mark Brown was grasping at what ever straws he could find to gain his " Andy Warhol" fifteen minutes of fame-- the Earth at Pluto's distance would not have "cleared it's orbit"--Jupiter hasn't-- and with five moons and a tectonically active crust Pluto is most certainly a planet


      1. h4rm0ny

        Re: Wishing and Hoping

        And honestly, why shouldn't it be a planet. Planet isn't a term that has any precise scientific meaning? No space probes will crash because they expected 2 Planets worth of gravitational force to affect them and there was only 0.5 Planets of gravitational force. It's not a scientific term, it's a cultural one. You want to correct someone who calls a hyena a canine because it's not? Fine - there are precise meanings behind the term. But there's nothing that says "planet = Xkg in mass".

        It's been a planet for most of its existence and it's really just a cadre of people who like correcting others that took it up as a crusade. Call it a planet, no-one will get confused. In fact, confusion and arguments will drop. And I say all this as someone who back in the day argued fiercely against metric KB and KiB inventions - they affected me as an engineer. But what the Hell is the scientific definition of "planet". It's just a layperson's term so let 'em have it.

        1. Shonko Kid

          "Call it a planet .... and arguments will drop."

          Perhaps that's the point. I thnk every sufficiently large community needs it's own 'flame war' talking point, and this is just theirs, giving them something to argue about at conferences, write papers and books on, and keeping them on the talk-show circuit for life!

        2. mhenriday

          Re: Wishing and Hoping

          «It's been a planet for most of its existence ...» Really ? For most of its existence - do you mean since it was detected from Earth by Clyde Tombaugh in 1930 and given the name Pluto later that year after a suggestion by an English schoolgirl ?...

          I suspect that this body has been around much longer than the 85 years since it was first classified as a «planet» and that the definition of the term is subject to change, as our knowledge of the star system in which we live increases....


      2. Dagg

        Re: Wishing and Hoping

        >The fact that Pluto has a techtonily active crust (Mercury and Mars don't) should rank Pluto above them on the planet list

        No, there are moons Europa and Titan that have tectonically active crusts that are bigger than pluto.

    3. Vatnos

      Re: Wishing and Hoping

      I think the "dwarf planet" category makes good sense, but I think they applied the term the wrong way. Dwarf planets should be seen as planets the same way giant planets and terrestrial planets are seen as planets. It's just another way that a planet can be. So what if there end up being 30 of them? The universe doesn't care about whether dumb schoolkids can memorize names.

      I don't have any particular emotional investment in Pluto's planethood. I dislike the IAU's definition for other reasons. Partly, I think the decision was made when it was thought a lot more objects like Pluto would be found in the Kuiper Belt, but so far we've only found 1. The rest are a good bit smaller, and there's only a 1 in 3 chance of finding any more. The other reason is that it seemed like the decision was based on anthropocentric thinking rather than scientific thinking: "keeping the numbers low and human-sized" rather than describing objects based on... what they living are.


      Instead of the IAU definition I think there should actually be two new categories instead of one:

      Dwarf planets - which should be Planets with a capital P - things like Pluto and Eris, that are large enough to be geologically active and dynamic, but are small and composed of ice, and located in a belt with other similar objects.

      Protoplanets - basically everything else below 2000 km but above 800 km in size. These objects (like Ceres) are large enough to form a sphere but small enough that they remain inert their whole lives. These would be considered a step up from comets or asteroids but they would be a rung below planets or even dwarf planets. Things like Ceres, Varuna, Quaoar would fit right in here nicely.

      I think this line of 'potential geological activity' makes more sense than the arbitrary orbital requirement--which doesn't even rule out Ceres from being a planet technically, as nothing else in its orbit is remotely close in size. Yet if we found something the size of Mars in the Kuiper Belt or the Oort Cloud (very possible), we'd have to consider that a dwarf planet due to this definition.

      1. BillG

        Re: Wishing and Hoping

        The IAU does not include a single planetary scientist and made a non-scientific decision with only a partial membership there to vote.

        Astronomy inspires and motivates us. I spent my youth looking at the stars. As a degreed scientist, I choose to not recognize the IAU's decision.

      2. Anonymous Coward
        Anonymous Coward

        Re: Wishing and Hoping

        I dont think "protoplanet" would be a good term for the Ceres-like objects. The "proto" part in todays language implies it was in the process of becoming a planet when it halted for some reason. Like a prototype.

        From what we now know of Pluto, once the atmosphere and ice has ablated in however many million of years it is very likely to be just a geologically inactive round ball much like Ceres. So just like a bunch of asteroids can apparently clump together into a planet, so can a dwarf Planet erode away into a ... whatever.

    4. John Brown (no body) Silver badge

      Re: Wishing and Hoping

      "there could be many other planets in the Kuiper Belt of comparable size"

      Asteroid Belt 2.0? (Currently in beta test)

  2. Your alien overlord - fear me

    IAU voters were in the main, astronomers who deal with galaxies and the like, planetery scientists should be the ones to decide if something is a planet.

    It's like having road builders decide a BMW is not a car because it is't made of tarmac.

    Yes downvoters, that is how rediculous the dsciption and subsequent vote was.

    Where's my I love Pluto icon?

  3. Anonymous Coward
    Anonymous Coward

    The Sun and Moon ...

    ... were once considered planets - see Dante's Paradiso.

  4. iLuddite

    more than a planet

    Active geology, atmosphere, seasons and several orbiting moons may qualify it as a planetary system, not just a planet. Sometimes size does not matter.

  5. ZSn


    You forgot one vital thing - it was the only 'planet' found by an American. The most vocal critics of this decision are found in the USA. Chauvinism is alive and well in science the same as any other human endeavour.

    The seasons and activity argument is frankly ridiculous, titan is bigger and also has weather - ideas it a planet as well?

    1. Captain DaFt

      Re: American

      "titan is bigger and also has weather - ideas it a planet as well?"

      If Saturn ignites and becomes a sun, yes. Until then it's just a moon.

      1. asdf

        Re: American

        >If Saturn ignites and becomes a sun

        Too bad it's Jupiter that has the Monoliths. For the record not all Americans are slaves to nationalism. Pluto is not even close to the most interesting TNO in this American's opinion (Sedna on the other hand and not because it was discovered by another American either).

      2. ZSn

        Re: American

        And Ceres is spherical - that still doesn't make Pluto a planet

        1. Roq D. Kasba

          Re: American

          Two American states have passed legislature stating that it is a planet. Famously, didn't one US state pass similar legislature that π=4 at some point? Doesn't really bolster the case.

          That said, I'm in team planet, because why the hell not.

          1. Graham Dawson Silver badge

            Re: American

            No, it didn't. You're thinking of the failed Indiana Pi Bill, a legislative attempt to square the circle - something politicians and legislatures around the world have been attempting to do in one form or another ever since they were invented. It was just rather more literal in this case.

          2. h4rm0ny

            Re: American

            I upvoted you just for "Team Planet". Beats the Hell out of "Team Downgrade Classification".

    2. h4rm0ny

      Re: American

      British support of Pluto's Planethood right here. Don't be so xenophobic. At best, I think you're just suffering confirmation bias from the fact that this is more of a controversy in the USA. In most of Europe and Asia, most people still just think of it as a planet so of course you'll see less argument.

      I don't care if an American discovered it. I don't discount Venus because a bunch of Sumarians or Mayans first documented it.

    3. John Brown (no body) Silver badge

      Re: American

      "You forgot one vital thing - it was the only 'planet' found by an American. The most vocal critics of this decision are found in the USA."

      ...and should have the least say since their country (the state, not the geographical place) hasn't even been in existence for a full Plutonion year yet!

      1. Anonymous Coward
        Anonymous Coward

        Re: American

        > Here in the US both New Mexico and Illinois have passed legislation that has explicitly defined Pluto as a planet.

        Typical American arrogance. Whether you agree with the classification or. not, you can't go making laws about it.

        Have they made laws on whether global warming exists yet? Or if God is real. etc.

        Anyway, if they really have that much free time, maybe their numbers should be culled, or they could be working on ways to make it even easier for cops to murder black people, or maniacs to get guns

        1. Anonymous Coward
          Anonymous Coward

          Re: American

          Mummy give baby too much sugar?

  6. Anonymous Coward
    Anonymous Coward

    The Designation of needs to be down graded

    The revelations of the the surface and materials of the Kuiper Belt Object shows that it is only a larger version of those objects that visit the inner Solar System with hopefully a stable orbit.

    The new designation should be C2015-New Horizon - that is a COMET

    1. Allan George Dyer Silver badge

      Re: The Designation of needs to be down graded

      Upvoted, not because I agree, but for your chutzpah. If you start a trend, we might be re-designating Mercury as a failed comet.

  7. Jordan Davenport

    IANAA, but...

    The classification of "dwarf planet" doesn't mean the thing isn't interesting or doesn't deserve studying. Mass, volume, and composition aside, my biggest remaining objection to considering Pluto a fully fledged "planet" is actually part of what makes it interesting - its orbit. The eight planets all orbit within a few degrees of the same invariable plane. Pluto on the other hand orbits at a fairly steep inclination compared to the other planets.

    Why is this? What can Pluto and the other Kuiper belt objects tell us about the formation of the Solar System? Could we maybe have at one point had a sibling star or two that have since drifted away? Could interstellar space be a little less empty than we thought?

    By all means, study Pluto. Don't take a diminutive reclassification as an affront to your research, and most importantly, don't think that only something as grandiose as a planet or star deserves study. Just don't claim it deserves to be in the same rank as the terrestrials or gas giants because it's not just a boring ball of rock and ice orbiting the sun.

    1. graeme leggett

      Re: IANAA, but...

      could we reclassify it from a dwarf to an "eccentric planet"?

      1. I ain't Spartacus Gold badge

        Re: IANAA, but...

        No. It can be a mad planet though. That will only change if we discover gold, platinum or diamonds there. Only once you're rich, do you qualify as eccentric...

  8. disorder

    I rather don't explicitly care whether it is, or isn't. I just want a decision not made by 'the public'. (The moronic kind; that legislate that it's a planet, or that PI=3 (really)) Because they can't (consistently) have Pluto and not Eris. And Quaoar. And several others they won't be able to pronounce with any more credulity, than when they ask to see pictures of Uranus.

    This was, more or less the reason for the (contrived) definition that IAU got, and in fact I think it's fine; that it means 'planet' tells you something about the /solar system/ because of the implied orbital dynamics (Kuiper Belt - is not the same region as where a few trojans are hanging around - neptune shaped it). Not just that it's a ball of whatever (or literally, just a ball). Whether or not that definition makes sense for any other solar system (and IAU already said it doesn't), being something else entirely.

    Pluto is clearly a world more fascinating than we could have hoped for (and Triton set a few expectations has Pluto roundly beat). And there's more than just it out there, that is even within our reach.

    I don't think the classification degrades it (many seem to). I think it's solveable, as a matter of emphasis.

    'The public' let's be realistic after all has no appreciation of what these bodies are, or if they do, it's as those nice pictures that are all more or less the uniformly biggest sphere that could fit on the page, or from bad (or less bad) TV sci fi shot in studios at 1G.

    But (as I'm sure many here actually know) ref: - they are - severely - not the same size. At all.

    What is _your_ minimum cut off going to be? Every grain of dust?

    There are arguably only two 'major' terrestrial planets in the solar system, based on what it'd mean to us to try to run on it (rather than hop) without faceplanting. I'm not saying that's what I'd pick. But in PR terms there'd then be 7 rocky planets - two major ones. and 4 giants (2 gas, 2 ice) and you can call that 11 if you want, and a lot of dwarves.

    Sooner or later each press place with only humanities grads trying to figure it out will use a different number, and people (americans) will stop caring. While highlighting at the same time, that the amazing thing, is that these bodies are *nothing* alike and thus worthy of a lot more space flybys and orbiters.

    Most (all?) other astronomical classifications get away with not changing, and noone cares (see supernovae, star spectral class, etc). But WIMPS still can get on with finding their MACHOS regardless.

  9. revilo

    Nomen est omen

    The change the nomenclature was little minded. There are many things which technically should be called differently, even in mathematics. But why complicate things and change established names? Removing the planet status was silly. A tomato is considered a vegetable even so technically, it is a botanical fruit. It would be equally cranky to demote the tomato of its vegetable status. The same fanaticism is sometimes also applied to language, where spellings can be inconsistent. Does this warrant to change the vocabularies and books? Correcting them produces more problems instead of leaving it and keep a bit of culture. When developers of programming languages pull such stunts and remove inconsistencies in well established languages, they even risk to kill the language because all previously written code needs to be adapted.The fact that Pluto was considered a planet was culturally and historically grown. Instead of applying a hair splitting and cold definition, one should have taken the history into account. Science is grown, built by humans and it does not help science to be pedantic. The Pluto name change story shows however that many folks care and feel strongly about such things. And that is nice.

    1. Charles 9 Silver badge

      Re: Nomen est omen

      The thing is, when it comes to science, precision matters. Science MUST be pedantic or mistakes linger. Once upon a time, the Church taught that the Earth was the center of everything; everything had to change then, too, didn't it?

      That's why botanists distinctly classify the tomato as a fruit (more specifically, a berry like its cousin nightshade). Now the debate about Pluto continues with the thought of a new reason to classify: geologic activity. I mean, are there other Kuiper Belt Objects with atmospheres and active geology and so on? Is Erin geologically active, for example? Let the debate rage, I say. If textbooks have to be changed, then that's the price of progress. Is it worse to correct a big mistake than to let people live in incorrect ignorance?

      1. h4rm0ny

        Re: Nomen est omen

        >>"The thing is, when it comes to science, precision matters. Science MUST be pedantic or mistakes linger."

        Sure. But planet has next to no scientific meaning. When you're calculating the path of your spaceprobe, you factor in 1x10^6Kg mass to your slingshot calculations, not "1 planet".

        Planet is a cultural term used by laypeople.

    2. J.G.Harston Silver badge

      Re: Nomen est omen

      "Vegetable" is a culinary term, not a botanical term, so it can overlap with several botanical terms.

      1. Ian Easson

        Re: Nomen est omen


        "Vegetable" is a biological term that has been grossly misused as a culinary term.

        For example, the following are biological fruits (because they contain embedded seeds), although in common culinary terms most people mistakenly believe them to be vegetables:

        - Tomatoes

        - Eggplant

        - Cucumbers

        The reason for this misidentification is that most people associate "fruits" with things that are "sweet".

        1. Charles 9 Silver badge

          Re: Nomen est omen

          The same problem exists with nuts. From a culinary perspective, it's an edible seed, but from a botanical perspective, nuts are a specific kind of edible seed that grows on trees and has no outer flesh, among other qualifications. Thus you end up with culinary nuts that aren't botanical nuts, like almonds and pistachios (drupes: they have outer flesh so are really the single large "pit" of a fruit) and peanuts (legumes: it's the "pea" part that is botanically accurate) and cashews (straight seeds of a fruit, not to mention toxic in raw form).

        2. Ken Hagan Gold badge

          Re: Nomen est omen

          I think you'll find that people have been cooking for quite a lot longer than they've been classifying things in biology. So the culinary definition got there first and the biologists borrowed it *knowing* that it didn't cover exactly the same ground as they wanted, but it was close enough.

        3. Frumious Bandersnatch Silver badge

          Re: Nomen est omen

          re: Is "vegetable" a culinary or biological term?

          I think you missed the point there, Ian. The OP said that "vegetable" is a culinary term and you disagreed by talking about fruit. What is this specific biological use of the word "vegetable" that you think that people are abusing? I think that, biologically speaking, "vegetable" is so broad as to be impossible to misapply. I think that, rather, your real beef is with people not knowing what a fruit is (and probably, by extension, the common fruit/veg dichotomy).

          Personally I have no problem with a word having two meanings depending on context or field. I know that things like tomatoes (and other crops from the nightshade family apart from stuff like tobacco and potatoes whose fruits are poisonous), all the squash/cucurbit family, rose hips/haws and even beans are technically fruit in the biological/horticultural sense, but I've no problem with these things being "misclassified" in the fruit or veg aisles at the supermarket. No more than I mind people saying that "the Internet is down" or similar.

          Reminds me of the saying (no idea who came up with it) that "knowledge is knowing that a tomato is a fruit; wisdom is not using it in a fruit salad."

          As it is with fruit, the same could be said for Pluto. Some experts might use a specific definition of what a planet is, but it doesn't stop the general public having their own ideas, too. Who cares if a bunch of astronomers use the word "planet" one way? The only place where the "correct" definition makes any difference would be in exams, pub quizzes and dictionaries and, frankly, none of these holds any sway over me.

    3. TheOtherHobbes

      Re: Nomen est omen

      Perhaps we should reclassify Pluto as a fruit?

      1. Paul Woodhouse

        Re: Nomen est omen

        I want to know how many swallows it would take to carry a Pluto 100km

  10. Chris Miller

    Categorisation isn't a problem that's unique to astronomy. There are countless objects within the solar system - some orbiting the sun, some orbiting each other* - and whatever human-imposed dividing line we choose, there will be objects in one class close to the boundary that have more in common with objects in the other class than those in their own.

    Pluto is simply the largest (as far as we know at the moment) 'dwarf planet' rather than the smallest 'planet', but the distinction is a purely linguistic one and makes no difference to the properties of the object itself.

    * Even this distinction isn't completely clear cut, 'Trojan' objects (at L4 or L5) can be considered as orbiting the sun or their neighbouring planet.

  11. Byz

    Categorisation is human trait

    Over the years I have worked on many systems where the client wants to categorise something.

    Generally it works for man made objects, however like all things there are exceptions (is an infrared lamp a lamp or a heater? It's technically both people don't like this)

    If you look at the planets each on is unique in some way, but we just like putting things in a box.

    If you work extensively with logic you begin to realise that categorisation is a cognitive thing rather than real. You can write the same program in procedural, object oriented, functional and protocol oriented paradigms they are all isomorphic with each outer it is just a different way of categorising a problem.

    Personally under the dwarf planet definition I would shove Mercury in there as it so close to the Sun that the Sun clears the region (it also almost cleared out Mercury as it used to be bigger, like Pluto).

    So it is just a putting it in a box exercise, driven by administration not science. Light used to be just a wave in the 19th century until the photoelectric effect was discovered and Einstein screwed it all up with the photon :)

  12. David Roberts


    It has been suggested that our Moon (up there in the sky) may no longer fit the formal definition of a moon, but might be a dwarf planet in a binary system with Earth.

    Given that it gave the name to the class of objects currently described as moons this does make the whole naming argument a little surreal.

    1. Ken Hagan Gold badge

      Re: Moon?

      If the Earth was less massive, the Moon would be a double planet. Same object, but the difference lies elsewhere. If Titan orbited the sun, it would be a planet. Same object, but the difference lies elsewhere. Meanwhile, Jupiter and Mercury are both planets. Vastly different objects, but the similarity lies elsewhere.

      As long as you insist on using one word to describe both the object and its position, you can't escape this nonsense, since an object and its position are only weakly correlated (by whatever rules govern the origin of solar systems).

      Personally I'm quite happy to describe Pluto, Titan and the Moon as planets when I'm concerned with their geology, moons when I'm concerned with their orbit. (Pluto is a "double moon", a satellite of both the Sun and Neptune. There's no word for it, but it *is* rather awesome, so there should be. In fact, perhaps that's what the word "Plutoid" should mean.)

      1. rfif1541

        Re: Moon?

        I don't see how Pluto could be a satellite of Neptune if it doesn't orbit it. Also because Pluto Crosses Neptune's orbital path I think we need to declassify Neptune as a planet because it hasn't cleared its path around the sun. When some say there are moons bigger then Pluto so they should be planets. NO these moons orbit a planet Pluto orbits the sun. Mercury is just a little bigger than our moon so it should be classified as a moon orbiting the sun. Ganymede is 3273 miles in diameter mercury is 3032 miles in diameter. again Mercury is a moon orbiting the sun. Mars is 4212 miles in diameter so its not a planet it is a moon that escaped Jupiter's gravity. So its just all stupid Pluto is a planet, its just a small planet. We are so privileged. This generation is the first humans to set eyes on this amazing planet. For me its special I'm over 60 yrs old and most of my life Pluto was the 9th planet. I never dreamed I'd live to see it. So let me go on believing that Pluto is a planet. I envy you young people you will probably see man set foot on Mars. Maybe see habitats with humans living and growing crops It will be an amazing time. I love space so much but was born in the wrong era.

    2. VinceH

      Re: Moon?

      But the moon is neither - it was revealed in the Doctor Who to be an egg!

      1. Ken Hagan Gold badge

        Re: Moon?

        That episode isn't canon. A special meeting of the International Who Fanclub declared that despite airing as part of an the official series, it had failed to clear its plot of debris.

        1. VinceH

          Re: Moon?

          So it's only dwarf-canon, then?

        2. BuckeyeB

          Re: Moon?

          A lot of episodes fail to clear its plot of debris.

  13. Christoph

    Any Kuiper belt object big enough to be round is a planet!

    OK, how many planets are there in the Solar System?

    Err, we don't know. We have a very vague guess at lots and lots.

    OK, how many planets do we know about?

    Err, we're not sure. Some of them are just blobs of light. We don't know how big they are. Or how massive they are. So we don't know whether they are big enough to be round. And anyway some of them might look big but actually be two or three separate small bodies orbiting each other.

    OK, what sequence are they in, counting outwards from the Sun?

    Err, we have a rough idea, but we're not sure of some of the orbits, and the orbits are so angled that the distances overlap.

    But we do have a list of definite possibles we can put in school textbooks?

    Err, no, because the list keeps changing as we get better observations.


    We need a word to describe the eight inner planets - the four rocky planets and the four gas giants. The things we usually think of as planets. Now we could invent a new word for those, and use 'Planets' for those plus Ceres plus the Kuiper belt plus anything else we haven't found yet. But that would mean persuading the public to use that new word. Ain't going to happen.

    So call those eight 'planets', and use a new term for all the rest. Anything else just isn't going to work.

    So do we include Pluto? Even though there are almost certainly many K-belt objects that are larger and more massive?

    It just doesn't make sense. It needs a much better justification than some US States made a law about it, or lots of people saying "I want it to be a planet, and I'm going to hold my breath until you change your mind, so there!"

    It seems to be pure sentimentality. So are schoolchildren in a few hundred years time going to ask "Why is Pluto a planet when all the other similar objects in this Solar System and other Solar Systems are not?" and be told "Well some people in the 21st Century screamed about it, so we messed up the whole classification system just to shut them up."?

    1. Ken Hagan Gold badge

      You appear to have argued the case for the opposite of your conclusion.

      Why is it a problem that you can't yet write down a list of all planets in your textbook? Why should Mercury and Pluto be classified as different kinds of object because of their historical discovery?

      Well some people in the 21st century screamed about their textbooks, so we messed up the whole classification system just to shut them up, er...

  14. Joey

    It's no big deal

    Planet, Dwarf Planet. It's just a small planet – just as a 'dwarf' if a small man. What's wrong with that?

    1. hplasm Silver badge

      Re: It's no big deal

      Well, to shut up the debate, we could agree that the 'dwarf' bit is silent, and just call Pluto a ... planet.

      Or we could invoke Stallman and call it GNU/Pluto - that would certainly lead to it being called a planet by most people, just like now.

      After all, to paraphrase a wise elephant- "A planet's a planet, no matter how small..."

      1. Anonymous Coward
        Anonymous Coward

        Re: It's no big deal

        > Or we could invoke Stallman and call it GNU/Pluto - that would certainly lead to it being called a planet by most people, just like now.

        I'm assuming you meant to write "GNU/Planet"!

    2. Ken Hagan Gold badge

      Re: It's no big deal

      The problem is that not content with driving a coach and horses through established pop culture, the IAU drove through the English language as well. A dwarf planet is defined to be not a planet. "Dwarf" is not an adjective. "Dwarf planet" is a double-barrelled noun.

      1. Anonymous Coward
        Anonymous Coward

        Re: It's no big deal

        Dwarf is an adjective.

  15. stuartnz

    Once again Randall Munro is on point

    With his suggested name for the new super-Earth

  16. x 7

    not a dwarf, its a PORG

    FFS, don't you know how offensive the term "dwarf" is?

    The proper phrase should be "planet of restricted growth" or PORG for short

    1. Charles 9 Silver badge

      Re: not a dwarf, its a PORG

      Well, it's a whole lot less offensive than "midget". Given the choice between the two, someone in such a position would probably prefer the term "dwarf," as there's enough etymology behind it to make it more neutral, especially since the term "dwarfism" is already in the medical textbooks, lending it more neutrality via the clinical definition.

  17. Alan Mackenzie

    This isn't science

    Pluto is a particular lump of rock and ice in orbit around the Sun, and whether we classify it as a planet or a dwarf planet makes not the slightest difference to what it actually is. I'd be happier if the alleged scientists would just keep themselves out of such an inane and fruitless debate. Lets instead enjoy our increased knowledge about Pluto and the outer Solar system.

    1. alain williams Silver badge

      Re: This isn't science

      A rose by any other name would smell as sweet.

      Let's get on with looking at the great pictures from New Horizons.

    2. Jamie Jones Silver badge

      Re: This isn't science

      " such an inane and fruitless debate"

      Of course, that should technically be vegetableless debate.

  18. Ilmarinen

    Re: not a dwarf, its a PORG

    Just what I was going to post. Have an up-vote.

    IMO, using the "D" word is just Dwarfist and unacceptable in the 21st centuary.

  19. Hero Protagonist


    Quasi-Planet, or "kewpie". So you've got 8 planets and a bunch of kewpies.

    Then you can make kewpie dolls.

  20. Bobcat4424

    They were correct

    The reason for removing Pluto from the list of planets still remains. The satellites of all planets, if present, rotate around the planet. But Pluto and Charon rotate around one another in a "dumbbell" configuration. Charon doesn't revolve around Pluto any more than Pluto revolves around Charon.

    1. x 7

      Re: They were correct

      If Pluto and Charon rotate around each other then surely they should be given the description of "binary planet". Its neither a normal nor dwarf - its unique in our solar system and deserves a unique title

      1. Charles 9 Silver badge

        Re: They were correct

        There's still the matter of Eris, which is supposed to be larger than Pluto.

    2. Martin

      Re: They were correct

      The satellites of all planets, if present, rotate around the planet. But Pluto and Charon rotate around one another in a "dumbbell" configuration. Charon doesn't revolve around Pluto any more than Pluto revolves around Charon.

      I happen to agree that Pluto shouldn't be a planet. But I don't think the argument that Pluto and Charon rotate around each other is relevant.

      Pluto and Charon rotate around the the centre of gravity of the Pluto/Charon system, just like, for example, the Earth and the Moon rotate around the centre of gravity of the Earth/Moon system. Pluto and Charon are much closer in mass to each other that Earth and the Moon, and so the centre of gravity is somewhere between them. In the case of the Earth and the Moon, the centre of gravity is about a thousand miles below the surface of the Earth.

    3. Six_Degrees

      Re: They were correct

      All pairs of bodies orbit "around" each other, tracing ellipses about their common center of mass. The moon orbits the earth in the same fasion; both gyrate around a point located just slightly below the earth's surface and far from the earth's center.

  21. Anonymous Coward
    Anonymous Coward

    Science doesn't determine EVERYTHING.

    It's not a scientific question as to whether Pluto is a planet or not. Venus, Mercury, Mars, et al. were planets before the ancients started speculating on their nature. They were simply... planets. If two states declare Pluto a planet, then it is a planet in those two states. If astronomers want a state research grant for Plutonian research, they better be very nice about how they fill out the application form.

  22. Mindbreaker

    Purely physical critera

    Greater than or equal to 2,000 km diameter, roughly spherical (or just not having any diameter under say 1,800 km), and orbiting the Sun...whatever fits, fits. How entertaining its geology is, is subjective, and prone to change as more is learned. Perhaps some mass minimum could be included. It probably should have a density above water (not counting atmosphere). We don't call chunks of ice floating in the ocean ships or islands, so it does not make sense to call a chunk of ice, a planet.

    You could have a few other requirements just for logic sake: not man made (or alien made), not already part of a planet, not made of 99% one element or compound, not something that already fits into some other class like: brown dwarf, star, pulsar, black hole, or other stellar object and it must have a sable and enduring orbit. Perhaps an orbital eccentricity smaller in extreme than the distance to the nearest star should be required. Or maybe, just an orbital period less than 1,000 Earth years, though that could be a little restrictive.

    1. Charles 9 Silver badge

      Re: Purely physical critera

      By those qualifications, though, we could end up jumping from eight to TEN planets. Recall the article mentioned Eris, which is larger than Pluto and just as round. Meaning in terms of size and roundness, if Pluto qualifies, so does Eris. About the only question mark with it is geologic activity. The probe has shown Pluto is geologically active, but we don't know the same for Eris.

      1. Ken Hagan Gold badge

        Re: Purely physical critera

        Charles 9: You seem to be implying that the IAU's decision on Pluto was principally motivated by a desire that there should be no more planets, ever. That seems, er, not just irrational but rather disturbed? Apparently it is so important to pull up the ladder that it didn't matter that Pluto was left behind in the rush.

        No matter. Time will tell. Future generations will land on these objects and go exploring. They will want a single, short word to refer to the object they are exploring. My money's on "planet", because "moon" implies a larger near neighbour and no-one (and certainly not the IAU) is even trying to come up with a third alternative.

  23. Martin Maloney

    A matter of urgency

    You're all missing the real issue here. The insensitive bullies of the IAU have victimized Pluto. Pluto is suffering a blow to its self-esteem.

    Pluto's downgrade from its classification as a planet was more than a grave injustice; the designation of “dwarf planet” is not PC.

    This abomination must be addressed forthwith!

    Therefore, in all humility, I submit for your consideration “circumferentially-challenged,” or if you prefer, “vulumetrically-disadvantaged.”

    Thank you for your kind attention.

  24. keithpeter

    Not in purple ink and not all in CAPITALS

    "Take Reg scribe Kieren McCarthy, who has a daughter born after Pluto was declassified. She's become so entranced with the recent news from Pluto that she writes letters to scientists asking for it to be reinstated again, based on how fascinating the place is."

    If I have read the article correctly, that puts the little girl around 9 or 10 so this is probably OK - especially if she puts drawings in that can go on the departmental fridge.

    I used to get letters from (chronological) adults IN CAPITALS and usually in purple or lilac ink claiming to have unified gravity and quantum mechanics, or to have disproved special relativity. One person that actually turned up at the lab insisted that she was sensitive to electricity and had to work away from power lines and could we 'test' her out and write a letter? The situation became slightly embarrassing when she told us that she had to catch the 3pm *train* back to town (yup - electric trains, 1kV traction power from overhead cables).

    Back on thread: its words folks. Read your Karl Popper. What matters is the thinking you do about how Pluto got to be like it is.

    Coat icon: mine's the one with a copy of The Logic of Scientific Discovery in one pocket and Medawar's The Art of the Soluble in the other.

  25. Tahuaya

    I am 71 years old and when I was in eighth grade, I got a science test question wrong, because I did not know that Pluto was a planet.

    If Pluto is not a planet, I want my test grade corrected.

  26. Adnan Al Shawafi

    Ten Reasons Pluto is not a planet

    *1- Does not has independent orbit around the Sun it cut the orbit

    of Neptune.

    *2- Pluto and Charon moving around the common center of gravity

    which has location outside the bodies of Pluto and Charon. So we can't say

    "Pluto is orbiting Charon or Charon is orbiting Pluto " also It is not fair

    to name one of them planet ( Pluto) and the second (Charon) moon follow

    Pluto where Charon has a powerful enough to move Pluto from outside its


    3- Pluto is not completely spherically as revealed by NASA "The

    new range is just west of the region within Pluto’s heart called Sputnik

    Planum (Sputnik Plain). The peaks lie some 68 miles (110 kilometers)

    northwest of Norgay Montes" In addition to a large terrain on the surface

    of Pluto, with respect to its size is a very large, although NASA hide a

    lot ofdetails about Pluto surface without gave us one full picture

    just which edited by painter ,that improve the condition of the

    International Astronomical Union to re-Pluto a planet , also the same

    thing about Charon .

    4- as well as Pluto does not have the strong gravity that enables

    it to be completely spherical because has two different faces ( the surface

    of Pluto's face that appears to Charon it has a different terrain in

    comparison with surface of other face), So we can say Charon's

    gravity affect the attractiveness of the surface details of the Pluto.

    5- Pluto does not have enough gravity to clear its orbit there are

    a lot of orbs in the Kuiper belt intervention in the planet's orbit Pluto


    6- Pluto only is not a planet because it is a binary with Charon.

    7- Pluto rotation around itself the day is equal to a month on

    Pluto ,So we can say Charon control the Pluto rotation and Charon remains

    free to turn around the itself.

    8- Pluto's orbit has a great anomaly in the orbit in orbital

    inclination around the sun and the big distance between the aphelion and


    9- Other satellites orbiting around Pluto and Charon does not

    around Pluto only or Charon only because the common center of gravity

    control orbits of these satellites.

    10- Pluto and Charon the enters the dance which NASA called it compound

    orbital dance without explain why those dance and her first interpretations

    that Pluto's mass is not concentrated in the center of the planet. In other

    words, if we break it into halves, we will see that one half has larger

    mass than the other half by over 20%, and the second interpretation,

    according to the hypothesis of compound balance balls for the researcher

    Adnan Alshawafi that orbital dance because Pluto and Charon not completely

    spherical there are large terrain is the surface which working on

    different area between Pluto and Charon opposite faces (Pluto's surface

    perspective from Charon and Charon's surface perspective from Pluto)

    The truth that must defend it and circulated among the members of IAU is

    "Pluto and Charon is a binary planet"

    1. h4rm0ny

      >> 1- Does not has independent orbit around the Sun it cut the orbit of Neptune.

      Nowhere in the history of the use of the word planet has anyone ever said it's something that cannot overlap with another planets orbit. Until post-fact looking for reasons to add this to the definition, of course. In fact, your argument is equally an argument that Neptune is not a planet. So are neither of them planets by your definition? If not, why is it okay for one to be ruled out because it cuts another planet's orbit but not the other? But chiefly, this is a post-fact addition to the definition of planet by yourself.

      >> 2- Pluto and Charon moving around the common center of gravity [...] also It is not fair

      All planets with satellites are orbiting around a common centre of gravity. Is the Earth no longer a planet? Also, how is one unfair to a planet? Are its feelings hurt?

      >> 3 Pluto is not completely spherically as revealed by NASA

      Nor is the Earth. It is oblate. This is another post-fact criterion added by yourself.

      >> 4- it has a different terrain in comparison with surface of other face

      Again, I don't think the word planet has ever had uniformity of terrain as a criterion, until you needed to add things to the definition to separate out Pluto.

      >>> 5- Pluto does not have enough gravity to clear its orbit

      See 4.

      >> 6- Pluto only is not a planet because it is a binary with Charon

      You can't have a binary planet? If you had two Earth-sized planets orbiting each other and both orbiting a star, would they no longer be planets?

      >> 7- Pluto rotation around itself the day is equal to a month on Pluto

      See 4. Also, I'm reasonably confident that there are asteroids that the inverse would be true of - fast rotation much less than their month. Are you arguing that they are therefore considered for the position of planet? Of course not, so it's a double standard not relevant to this.

      >> 8- Pluto's orbit has a great anomaly in the orbit in orbital inclination

      And Uranus' axial tilt is nearly perpendicular to the rest of the planets which is far more of an anomaly. So what? Again, see answer to 4.

      >> 9- Other satellites orbiting around Pluto and Charon does not around Pluto only or Charon only because the common center of gravity control orbits of these satellites.

      Just number 2 again with different wording. All planet and satellite systems orbit a common centre of gravity. Is there some established point agreed in the definition of planet historically that defines how displaced the common centre can be from a body before it disqualifies that body from being called a planet? Not that I am aware of. See answers to 4 AND 6 this time.

      >> 10

      Snipped for legibility. This is again just a longer re-wording of 6.

      1. David L Webb

        >> 7- Pluto rotation around itself the day is equal to a month on Pluto

        See 4. Also, I'm reasonably confident that there are asteroids that the inverse would be true of - fast rotation much less than their month. Are you arguing that they are therefore considered for the position of planet? Of course not, so it's a double standard not relevant to this.

        And why fixate on the month. Venus has no major moon and hence no month but its day is longer than its year.

  27. MichaelAS

    Etymology, people

    Why not just invent another term or phrase that encases Mercury to Neptune according to the definition that everybody is freaking out about, and let all known 'wanderers' that are spherical, orbit the sun and are equal to or greater than Pluto's size be deemed planets? That immediately will bounce Eris and a whole range of other objects out of the running and will keep scientists and (most) other people happy? The word 'planet' is just a word, after all.

  28. rf123

    Stern, before and after

    Alan Stern, BEFORE the New Horizons project to Pluto:

    "From a dynamical standpoint, our solar system clearly contains 8 uberplanets and a far larger number of unterplanets, the largest of which are Pluto and Ceres." - from 2002 paper entited "RegardinAg the criteria for planethood and proposed planetary classification schemes"

    Alan Stern, immediately AFTER the New Horizons project to Pluto was launched:

    "Firstly, it is impossible and contrived to put a dividing line between dwarf planets and planets." - 8/25/06 to BBC News

    So, you know, Pluto is a planet when he's leading a mission to it.

  29. JeffyPoooh

    Idiots Astronomical Union

    IAU says a 'planet'...

    1) is in orbit around the Sun,

    2) has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and

    3) has "cleared the neighbourhood" around its orbit.

    Earth has about 10,000 near Earth objects in its neighbourhood. .: Not a planet.

    Jupiter has about 100,000 Trojan objects in its neighbourhood. .: Not a planet.

    Neptune hasn't even cleared its neighbourhood of Pluto. .: Not a planet.

    Ganymede and Titan orbit a common CofG with their 'planets', while orbiting the Sun. .: Are planets.

    Extrasolar 'planets' do not orbit 'The Sun'. .: Those 1000s of 'planets' are not planets.

    .: The IAU are idiots.

    1. JeffyPoooh

      Re: Idiots Astronomical Union

      If they fix heliocentric blind spot of 'the Sun' (replace 'the Sun' with 'a Star'), then they'll need to think about binary star systems.

      Otherwise the two stars in many a binary star system would each be 'planets'.

      They will need to add a 4th criteria...


      4) isn't lit up like a zillion Xmas trees (or similar intent).

      That their definition is so clearly defective is an indictment of their basic thinking skills.

      That anyone would instinctively defend them as 'experts' indicates an embarrassing and unhealthy degree of 'deference to authority'.

      The IAU are idiots and deserve ridicule.

    2. bdeclerc

      Re: Idiots Astronomical Union

      Intepreting "has cleared its orbit" as "there's nothing, zip, nada sharing its orbit" is incorrect and specious, since that would mean nothing can ever be a planet.

      Earth's mass is about 1.7 million times all the other matter "sharing" its orbit (excluding the moon, since it orbits the earth)

      Neptune is about 50,000 times the mass of all the other matter "sharing" its orbit (and that includes Pluto) and is the least "planety" planet in the 3rd criterion.

      Ceres is about 1/3rd of the mass of all the other matter "sharing" its orbit, so it isn't even close to "having cleared its orbit"

      Pluto is at most 1/100,000th the mass of all the other matter "sharing" its orbit, so it is very much further away from matching criterion (3) than even Ceres is.

      And planets around other stars are called "exoplanets", not "planets", so strictly speaking there's no problem there.

      All objects orbiting another object "share a common Center of Gravity", in all cases (including Ganymede and Titan) that Center of Gravity is *inside* the main body, except in the case of Pluto & Charon where the Center of Gravity is outside of Pluto (Well, there are probably other examples if you look to small double asteroids, but Pluto-Charon is the only "big" couple where this is the case)

      So while the definition of the IAU may be contentious in some circles, it is by no means idiotic...

      1. JeffyPoooh

        Re: Idiots Astronomical Union


        By your logic, they should have included a mass ratio cut-off in their definition. But they failed to do so.

        In fact, they were bending over backwards to avoid including any arbitrary numerical values in the definition.

        So your excuse is a non-starter.

        The C of G argument clearly allows moons to be called 'planets' because they do meet the criteria.

        They failed to include wording about combined C of G being beneath a surface, or beneath the clouds of a gas giant. Meaning you'd have to assign another arbitrary cut-off as to the gas pressure at the altitude of the combined C of G.

        Another non-starter.


        Do they have 'dwarf exoplanets'?

        The binary star mind game still needs to be addressed, so that a star isn't called an 'exoplanet' because the IAU can't think clearly.

  30. Esme

    To quote myself in another thread:

    We live on a planet orbiting a star, our Sun. If you're not interested in astronomy, it may come as a surprise to learn that the Sun is a yellow dwarf star - because there are two types of star that are yellow, most of similar size to our sun, but some are flippin' ginormous, which are called yellow giants.

    Which doesn't make the Sun not a star, despite it being a yellow dwarf.

    Likewise, Pluto is a dwarf planet - it's a planet, but a little or dwarf one.

    Can we put the nonsense about Pluto's status to bed now, please? :-}

    I'd also add, for the benefit of those thinking that the Pluto-Charon barycentre being external to Pluto has some bearing on the matter, that viewed externally to the pair, Luna doesn't orbit Earth, it has an orbit around the Sun that is always concave with respect to the Sun (as Isaac Asimov rather wonderfully pointed out umpty years ago). Now, given Luna and Earth also revolve around each other, and that Earth is some 81 times as massive as Luna, no-one in their right mind would regard Luna as anything other than a moon of the Earth, irrespective of where the barycentre of the pair is, but the fact of the matter is that Pluto has a better grip on Charon than Earth has on Luna. Oh, and the astronomy books from when I was a child commonly referred to what we now call asteroids as 'minor planets' (as in minor 'wandering object', which is what planet means, in the sense of wandering against the background of the stars)

    IMO nothing horribly wrong with the IAU's current classification, when one stops to think about it; we live in a solar system of eight major planets, and quite a few lesser planets. Perhaps calling Ceres and Pluto minor planets rather than dwarf planets might sit better with some, and I'd be happy with that, too, as we'd then have Ceres, Pluto, Eris, etc as minor planets; Mercury, Venus, Earth, Mars as planets, and Jupiter, Saturn, Neptune Uranus as giant planets. All planets - just in differing categories of planets.

    And nothing but nothing about all this fuss about nomenclature is going to make one iota of difference to how fascinating the universe in our immediate vicinity is. Pluto has indeed proven to be a more fascinating place than we imagined it would, even based on what little we know about it now. There's more to come, and lots more to learn about our solar system in general, and what we call or how we classify any of it makes no difference whatsoever to what is actually out there. Let's get out there and see what we can find, eh?

    1. Charles 9 Silver badge

      Technically, Sol (the Latin name for our Sun, as good a scientific name as any) is Main Sequence: towards the low end, but still Main Sequence. Dwarf stars are typically much tinier than any Main Sequence Star.

  31. Stevie Silver badge


    In your face, DeGrasse Tyson!

    All time-wasting thing-renamers should now move over so real scientists can work at getting humans there for a proper look in a decent timescale.

    We need anti-matter and a way to store it economically, and we need it yesterday. Otherwise everyone will be stuck on this mudball listening to the time-wasting telescope-and-robot brigade forever.

  32. InNY

    We should

    ask Minnie about Pluto...

  33. gordonyx

    Who cares what Neil Tyson thinks. He manages a planetarium.

  34. Anonymous Coward
    Anonymous Coward

    New Horizons data has revealed a lot about the dwarf planet's history.

    So.... old Pluto is using Ashley Madison too, eh?

  35. Anonymous Coward
    Anonymous Coward

    Re. Pluto

    I thought it was the height of irony that Man's first probe to visit Pluto was powered by... wait for it.. plutonium..

    But apparently the latest theories doing the rounds suggest that superconducting hydrogen sulphide in Jupiter's outer core just might account for the enormous magnetic field without having to substantially rewrite the textbooks as the inner core is probably a combination of slush hydrogen and iron sulphides.

  36. Hoe

    Personally I think a planet should be a hard surface, if we can't land on it, it's not a planet.

    Gas Giants and anything else should be classified separately.

    I am no expert, but it doesn't sound like these guys are doing a great job at being either!

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Biting the hand that feeds IT © 1998–2020