back to article Amid new push to make Pluto a planet again... Get over it, ice-world's assassin tells El Reg

The ongoing argument over whether Pluto is an actual planet or just a dwarf on the outskirts of the Solar System has heated up again – with a new proposal to reapply planetary status to the distant iceball. In a vote in 2006, the International Astronomical Union (IAU) decided to reduce the status of Pluto to that of a dwarf …


  1. Anonymous Coward
    Anonymous Coward

    How DARE you!

    We of the Oort Cloud Alliance wish to express our greatest displeasure with these findings. There may be 200 dwarf planets in the Kuiper belt, all of which should be memorized and exalted by your Earth students!

    Make it so!

    1. Anonymous Coward
      Anonymous Coward

      Re: How DARE you!

      The Kuiper belt is much nearer than the Oort cloud.

  2. PacketPusher

    Large Satellites?

    By Stern's definition all of the large satellites would be planets too.

    1. DNTP Silver badge

      Re: Large Satellites?

      Yeah that's kind of an obvious problem, and when you get there it's mostly just sighing, facepalming, and but Tradition!, which is kind of the whole Pluto=planet argument anyway.

      But you have to be careful with the "sun orbit" requirement anyway, since pendants like myself will point out that the Jupiter-Sol barycenter is outside the sun, so technically they orbit each other.

      1. Mark Exclamation

        Re: Large Satellites?

        @DNTP - So, are you a necklace, a brooch, or something similar?

        1. DNTP Silver badge

          Re: Large Satellites?

          Well, I like to learn and comment about space science despite not being a space scientist, so in a sense reflect and refract the light of knowledge instead of generating it.


        2. Sorry that handle is already taken. Silver badge


          There are no pedants on The Reg, only loose-hanging pieces of jewellery.

      2. Astara

        Sun-Jupiter => binary system?

        Wouldn't that make sun-jove a binary? How far outside the sun is it (outside 1st planet, mercury's orbit)?

        1. Ken Hagan Gold badge

          Re: Sun-Jupiter => binary system?

          Apparently, the barycenter is at 1.07 solar radii, so it is only marginally above the solar surface. Still, for rhetorical purposes, that's enough.

    2. Mark 85 Silver badge

      Re: Large Satellites?

      But isn't a moon a body that orbits a planet? Maybe that needs to be put into the definition.

      1. julianh72

        Re: Large Satellites?

        So how do you deal with the Pluto - Charon system?

        Charon is spherical, and has half the diameter of Pluto (and about 1/8 the mass), making Pluto - Charon a binary system (much more so than Earth - Moon, for example). And the barycentre of Pluto - Charon lies WELL outside Pluto.

        1. plutosavior

          Re: Large Satellites?

          Pluto-Charon is a binary planet system.

      2. smartermind

        Re: Large Satellites?

        Or isn't the Earth a body that orbits the Moon? Just like two masses of whatever size have equal gravitational attraction, so two bodies in close proximity equally orbit each other. Because we earthlings have a geocentric viewpoint, we like to think the moon orbits the Earth but in fact they orbit each other and the Sun in a spiral corkscrew pattern. Likewise the planets orbit the Sun and together the bodies in the solar system orbit the Milky way in a corkscrew fashion.

        So, why shouldn't the Moon be classified as a co-planet!

        1. Esme

          Re: Large Satellites?

          @smartermind - Isaac Asimov, bless his memory, pointed out many years ago that there's something odd about the Earth-Moon system, and that is that the Sun exerts a greater pull on the Moon than the Earth does - a situation which, if memory serves me correctly, exists for no other moon in the solar system.

          Also, if you look at a projection of the Moon's motion from a heliocentric view, the moon and the Earth both orbit the Sun in intertwined orbits, and the Moon's orbit about the Sun is always concave.

          Given all that, despite the fact that the barycentre of the Earth-Moon system is just about within the Earth's surface, one could make a strong case for arguing that the Moon isn't a moon at all but the other part of a binary planet system along with the Earth.

          Alternatively, given the current ruling for what constintutes a planet, as the Earth clearly hasn't cleared its orbit of other sizable bodies (because of the Moon, which isn't actually a moon, one could argue as per the above), then the Earth isn't a planet, unless one counts a binary planet as a planet. (Which then fuels arguments about Pluto/Charon)

          And no, I don't think the Earth is not a planet, personally. It's just a MUCH harder thing to define than most people think, when you consider all the varied edge cases that can potentially exist.

          And frankly - the universe doesn;t care what we label things. They're out there, they're interesting, they're worthy of investigation, whatever the heck you call them :-}

        2. John H Woods Silver badge

          Re: Large Satellites?

          "Or isn't the Earth a body that orbits the Moon? Just like two masses of whatever size have equal gravitational attraction, so two bodies in close proximity equally orbit each other." --- smartermind

          They're rotating around their 'barycentre' or mutual centre of mass. However for Earth/Moon that point is below the surface of the Earth and for Pluto/Charon that point is well outside Pluto.

      3. VinceH Silver badge

        Re: Large Satellites?

        With a little thought, the definition could be updated in such a way that allows Pluto to be defined as a planet, but excludes the Moon (and those of other planets).

        If we take the proposed definition quoted in the article as a starting point:

        "A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters."

        The article notes two requirements from the 2006 definition which are the cause of all Pluto's problems:

        * Clearance of all other objects in the same orbit

        * Orbits the Sun

        The first of these is clearly imperfect because small objects can still exist on the same orbit as larger objects having not been cleared - even larger ones if they're sufficiently distant in that orbit, as this highly scientific documentary makes clear.

        Orbiting the Sun is also a problem because it doesn't allow for rogue planets, as noted in the article - and although we think of it as the moon, that time it went rogue (as detailed in this documentary) it should arguably have been considered a planet.

        So the definition could perhaps scope out whether or not it is orbiting a larger body, and if so the nature of that body. If it is orbiting a larger body that has never undergone nuclear fusion, it is a moon - otherwise it is a planet.

        That makes Pluto the planet, and Charon a moon - and because it doesn't specify that it must be orbiting a larger body, rogue planets can be planets too. If you want to take the barycentre into account, then it is the larger body of those that share a barycentre.

    3. Astara

      Re: Large Satellites?

      Isn't one of his requirements that it be spherical?

  3. Christoph Silver badge

    "A planet is a sub-stellar mass body that has never undergone nuclear fusion"

    Well that excludes Earth then.

  4. PNGuinn Silver badge

    I pee on your petty bureaucracy


    Planets first .... Reg units next?

  5. Paul J Turner

    Sorry Prof'

    'The Moon' IS a planet not 'A Moon'.

    If the Earth was to vanish it's orbit would continue pretty much unchanged.

    Also, It's long past bloody time that El Reg made it easy to include hyperlinks, or at least made the information on how to embed them clear, complete and easy to find.

    I think I found a reference once, but it assumed html expertise. Is a button that hard to implement?

    1. Red Bren

      Re: Sorry Prof'

      "Also, It's long past bloody time that El Reg made it easy to include hyperlinks, or at least made the information on how to embed them clear, complete and easy to find."

      From about halfway down the El Reg Forums FAQ:

      "You need to put in the code yourself. You are a techie. This is not hard."

      Troll icon, because I've just done the thing you've asked for help with, without explaining how I did it. But I don't know how to show an example of how you insert a hyperlink, without it appearing as a hyperlink!

      1. Paul J Turner

        Re: Sorry Prof'

        Thanks for your post with a link in it Red Bren. I used view-source and had a practice on an old forum post

        I tested with - <_a _ _h_r_e_f_=_"_h_t_t_p_s_:_/_/_c_9_._i_o_/_"_>_C_l_o_u_d_ _9_<_/_a_>

        take out the '_' characters

        I thought that there was some substitution of '[' and ']' for '<' and '>' but that may have been some other forum.

        1. Graham Marsden

          Re: Sorry Prof'

          > I thought that there was some substitution of '[' and ']' for '<' and '>'

          That was a forum that uses BBCode

          eg [url="http..."]El Reg[/url]

    2. Pascal Monett Silver badge

      Re: Sorry Prof'

      Thank you for that link. I learned that I had totally belonged to the group that imagined that the Moon orbited Earth, but it actually orbits the Sun with a bit of gravitational perturbation from that ol' ball of Earth.

      A disturbing perspective. I might, with the good help of my friend Jack, be able to drink that away and consider that lizard men are once again trying to conspiracy-theory influence reality, but that will take some time.

      In any case, I cannot shake the belief that the discussion around the planetary status of Pluto is more down to the fact that it is the only planetary body discovered by an American than any truly scientific discussion. Typical New World nuisances that have to have something important to their name since they only have a quarter of a millennium to show History.

      Personally, I find it much more logical to imagine that Pluto belongs to the undoubtedly large Kuiper Belt Objects group rather than consider it a Planet. Maybe adding another rule, something along the lines of "a planet cannot have a moon larger than one-half its mass" would quell the discussion (yeah, right).

      All of this will not keep Planet X from being called a Planet, though, as soon as we find where the bloomin' dale it is.

      1. plutosavior

        Re: Sorry Prof'

        Pluto is both a small planet and a Kuiper Belt Object. The two are not mutually exclusive. The first tells us what it is; the second tells us where it is. While the Kuiper Belt is composed largely of tiny, shapeless rocks and balls of ice, it does host some small planets too.

  6. Red Bren

    "But you have to be careful with the "sun orbit" requirement anyway, since pendants like myself will point out that the Jupiter-Sol barycenter is outside the sun, so technically they orbit each other."

    I thought one of the reasons for Pluto's demotion was due to its barycenter with Charon being beyond its radius.

    On a further point of pedantry, the fact that the Jupiter-Sol barycenter is outside the sun is why the sun is not classed as a planet...

    1. Voland's right hand Silver badge

      Not just that

      Even Jupiter has not cleared its debris - there is plenty of it (some of it km in size) sitting at both Lagrange points ahead and behind Jupiter revolving around the sun using the same orbit.

  7. Anonymous Coward
    Anonymous Coward

    Brown Dwarves

    Yea!! A great proposal as this demotes "Brown Dwarves" to planets where they should belong.

  8. Dagg

    Pluto Also tidally locked to Neptune

    It has the same orbit period and crosses in and out of Neptunes orbit which means if it is promoted back to a planet it means that and Neptune and it will be swapping between planet position 7 and 8.

    Pluto is is also not on the ecliptic....

    1. Ken Hagan Gold badge

      Re: Pluto Also tidally locked to Neptune

      It is a pity that we have no name for a body that is in such a relationship. It was always the weakest point about the orbit-clearing business. Neptune has cleared its orbit. That Pluto survives is because it is in an orbital resonance and therefore is never in Neptune's path.

      Wikipedia informs me that Laplace was the first person to analyse such systems so perhaps we could call Pluto a Laplacian moon of Neptune. Astonomers who care about orbital relationships can hang on the word "Laplacian". Planetary scientists who care about geology can hang on the word "moon".

  9. Anonymous Coward
    Anonymous Coward

    Yeah but... wanna hear what Pluto calls us!

  10. MrDamage

    Demote Neptune as well

    After all, anything that slides out past your anus can no longer being described as part of you, anything beyond Uranus should not be counted as a planet.


    1. Dr. G. Freeman

      Re: Demote Neptune as well

      So Neptune, Pluto and anything else we find out there are Dingleberries then ?

      1. Intractable Potsherd

        Re: Demote Neptune as well

        Dr Freeman - I think you have succeeded in ending the debate. Dingleberries it is!!

  11. Neil Barnes Silver badge

    Planet = wanderer

    Planetesimal = broken bits.


    (apropos of nothing much, as Pluto crosses Neptune's orbit, then obviously Neptune hasn't cleared its orbit either, and therefore isn't a planet either.)

  12. R. B.

    Did they just call Pluto a world?

    " many other objects in our solar system – is a fascinating little world,..."

    Um did they just call Pluto a "world"?? Sounds like a planet to me ! Curse you Neil Detyson- Grason ( spelling ?) - just kidding anyways!! Lol

  13. MikeRoch

    9-planet Orrery

    I've just had a 9-planet Orrery with orbiting moons made by a UK engineer ... which of course includes Pluto. Should Prof. Michael Brown ever drop in for tea I can easily detach the Pluto arm to avoid ruffling his feathers. Joking aside, I foresaw the possibility of the reinstatement of planetary status to Pluto so decided that including it in the Orrery was justified.

    Google "Genesis Orrery Staines & Son" to see the beast

    1. Nick Ryan Silver badge

      Re: 9-planet Orrery

      That must have been a fine bit of orrery engineering if it also included an approximation of Pluto's solar orbit - being on a different plane and swapping places with Neptune must be a bugger to engineer :)

  14. Ag2C2

    Spaceflight & Man's First Friend

    On February 18 in 1930, Clyde Tombaugh discovered Laika, the dwarf planet previously known as Pluto.

    Working on that petition to the IAU's Committee on Small Body Nomenclature (CSBN) that challenges old habits and vested interests.

  15. Milton Silver badge

    How many angels can dance on the head of a pin?

    Because that's what this "argument" puts me in mind of: a bunch of evangelists arguing about something that really just does not matter.

    Like many Reg readers I'm keen on science, and as such I would have thought there were at least 1,000 things about The Body Known As Pluto which are worth finding out, not a single one of which depends upon whether some accidentally evolved crania full of blue mush six billion miles can't agree whether to label it as a planet, dwarf planet or scubble-wang-doo.

    "A difference that makes no difference is no difference"

    1. I ain't Spartacus Gold badge

      Re: How many angels can dance on the head of a pin?

      So as I understand it what you're proposing is a solution where all can save face. So yes, Pluto is a planet. Except we're changing the word planet to "scubble-wang-doo".

      Thus the next question, does that mean Pluto remains as a planet, along with perhaps Ceres and the like - leaving us with 8 scubble-wang-doos in the solar system? Or is Pluto also now a scubble-wang-doo as wee?

      1. Intractable Potsherd

        Re: How many angels can dance on the head of a pin?

        No - it's a Dingleberry (see post above by Dr G. Freeman).

  16. stephanh Silver badge

    just wait for the 9th planet

    If the hypothetical planet that messes up Kuiper object orbits gets actually discovered, it will almost certainly be

    1. a gas/ice giant, and

    2. a dwarf planet under the current definition (because of not "having cleared its orbit")

    Then the whole system will probably collapse under the silliness of having a dwarf giant planet.

    By the way, the Moon is not a moon, it's one half of a binary planet. Not sure which idiot called it Moon but it should obviously be renamed. I propose to call it the planet Minerva going forward.

    1. David Roberts Silver badge

      Re: just wait for the 9th planet

      Dwarf giant plamet?

      Perhaps a Carrot then?

      1. lglethal Silver badge

        Re: just wait for the 9th planet

        no, no, no... A Carrot would be a giant Dwarf Planet not a dwarf Giant Planet...

      2. MrDamage

        Re: just wait for the 9th planet

        Not a Carrot, but a Boo.

    2. imanidiot Silver badge

      Re: just wait for the 9th planet

      @stephanh, technically in science "the moon" is referred to as Luna afaik. (And yes, it's just latin for moon, but it atleast provides some distinction)

      1. stephanh Silver badge

        Re: just wait for the 9th planet

        @imanidiot, the IAU seems to disagree with you:

        "So the IAU does recognize official names for the major planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) and Earth's satellite (Moon)."

        Note that it is called "Moon", not "the Moon".

        Calling it Luna makes you sound like somebody who read too much Heinlein.

        And no, "Tellus" is not the official name of Earth.

        1. Rich 11 Silver badge

          Re: just wait for the 9th planet

          And no, "Tellus" is not the official name of Earth.

          Of course it isn't: that's Terra.

          1. imanidiot Silver badge

            Re: just wait for the 9th planet

            I thought it was "that thing down there".

            @stephanh, huh, learn something new everyday. I could have sworn the official name was Luna...


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