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posted by martyb on Saturday September 08 2018, @10:24AM   Printer-friendly
from the there-goes-the-neighborhood dept.

Pluto a Planet? New Research from UCF Suggests Yes

The reason Pluto lost its planet status is not valid, according to new research from the University of Central Florida in Orlando. In 2006, the International Astronomical Union, a global group of astronomy experts, established a definition of a planet that required it to "clear" its orbit, or in other words, be the largest gravitational force in its orbit. [...] [Philip] Metzger, who is lead author on the study, reviewed scientific literature from the past 200 years and found only one publication -- from 1802 -- that used the clearing-orbit requirement to classify planets, and it was based on since-disproven reasoning.

[...] The planetary scientist said that the literature review showed that the real division between planets and other celestial bodies, such as asteroids, occurred in the early 1950s when Gerard Kuiper published a paper that made the distinction based on how they were formed. However, even this reason is no longer considered a factor that determines if a celestial body is a planet, Metzger said.

[...] Instead, Metzger recommends classifying a planet based on if it is large enough that its gravity allows it to become spherical in shape. "And that's not just an arbitrary definition, Metzger said. "It turns out this is an important milestone in the evolution of a planetary body, because apparently when it happens, it initiates active geology in the body." Pluto, for instance, has an underground ocean, a multilayer atmosphere, organic compounds, evidence of ancient lakes and multiple moons, he said. "It's more dynamic and alive than Mars," Metzger said. "The only planet that has more complex geology is the Earth."

Planet Ceres, please.

The Reclassification of Asteroids from Planets to Non-Planets (DOI: 10.1016/j.icarus.2018.08.026) (DX)

Related: Pluto May Regain Status as Planet
Earth is a "Dwarf Planet" Because it has not Cleared its Orbit


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  • (Score: 4, Interesting) by dltaylor on Saturday September 08 2018, @10:31AM (18 children)

    by dltaylor (4693) on Saturday September 08 2018, @10:31AM (#732129)

    If it's going to be argued that Pluto is a "planet", then include all of the other objects we know of that fit. Don't just whine about Pluto.

    Also,the "round" thing includes a lot of moons, many also being active bodies, despite the hyperbole of the paper's author.

    I don't have any emotional ties to 8/9/10/100, but I'm tired of the "Pluto is a planet" crowd that does, making a special case for it.

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  • (Score: 4, Insightful) by isostatic on Saturday September 08 2018, @12:50PM (13 children)

    by isostatic (365) on Saturday September 08 2018, @12:50PM (#732174) Journal

    Lets drop the term "planet" for a moment

    The solar system has

    * A flamnig ball of gas (the sun)
    * Big balls of gas (Jupiter/Saturn/Uranus/Neptune)
    * Big balls of rock (Mercury/Venus/Earth/Mars)
    * Small balls of rock (Eris/Pluto/Ceres/Haumea/Makemake/and more)
    * Lumps of rock that aren't balls (Vesta, Hygiea, Ida, etc)
    * Balls of rock orbiting other balls (the moon, ganymede, titan, etc)
    * Lumps of rock orbiting other balls (Deimos, Dactyl, etc)

    Historically the term "planet" refered to the historical planets of Mercury, Venus, Mars, Jupiter and Saturn. Therefore we can assign the super-category "Planet" to
    * Big balls of gas (Jupiter/Saturn/Uranus/Neptune)
    * Big balls of rock (Mercury/Venus/Earth/Mars)

    Pluto, Eris, etc don't fit into those categories, they are orders of magnitude off the "Big balls of rock" category.

    • (Score: 4, Interesting) by theluggage on Saturday September 08 2018, @03:02PM (3 children)

      by theluggage (1797) on Saturday September 08 2018, @03:02PM (#732211)

      Historically the term "planet" refered to the historical planets of Mercury, Venus, Mars, Jupiter and Saturn.

      Historically, "planet" has also referred to any object that moved against the "fixed background" of stars, which would cover anything up to and including Russel's Teapot. Between 1930 and 2006 "planet" included Pluto - so what changed between 1846 and 1930?

      * Big balls of rock (Mercury/Venus/Earth/Mars)

      * Small balls of rock (Eris/Pluto/Ceres/Haumea/Makemake/and more)

      Beyond what radius/volume does a "small ball of rock" become a "big ball of rock"? Just bigger than Pluto? Or should it go by mass (a bit more massive than Eris)?

      So, sorry, your argument depends on "Historical" meaning "discovered before Pluto" and "big" meaning "bigger than Pluto". Not very scientific.

      If you want a "traditional" definition of "planet" just say "the planets are - by tradition - Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune and Uranus" and, I dunno, maybe use trial by combat to decide whether to include Pluto - or ask that octopus that predicts the superbowl winner. That's fine - just be upfront that its a historical artefact rather than scientific definition and don't try and pass off an arbitrary line in the sand as "science".

      As TFA argues: if you want a science-based definition, the "gravity strong enough to form a spheroid" criteria at least has some scientific significance.

      Problem is, at some stage the argument is going to have to turn to the categorisation of exoplanets (and there's already more known exoplanets than planets - fortunately, so far, they tend to be firmly in the big-balls-of-whatever category because we can't see the small ones - yet). Then, we'll have exoDwarfPlanets and will need to use CamelCase to make it readable - and nobody wants to see that!!!

      All hail planet Eris - except it obviously should be called Rupert [wikipedia.org] - the IAU just can't get it right, can they?

      • (Score: 2) by isostatic on Saturday September 08 2018, @03:36PM (2 children)

        by isostatic (365) on Saturday September 08 2018, @03:36PM (#732231) Journal

        Historically, "planet" has also referred to any object that moved against the "fixed background" of stars,

        Historical as in since man first looked up at the stars and saw wanderers - pre Galileo

        Beyond what radius/volume does a "small ball of rock" become a "big ball of rock"? Just bigger than Pluto? Or should it go by mass (a bit more massive than Eris)?

        Both size and mass wise the jump between Pluto/Eris and Mercury is enormous, more than the distance between them and Makemake/2007 OR10, and we believe we'll be finding far more objects in that region.

        I don't mind if you want to include Pluto in your definition of Planet, however you have to include Eris and any other similar objects as well. We then just need a new term to define "big planets".

        • (Score: 0) by Anonymous Coward on Saturday September 08 2018, @07:15PM

          by Anonymous Coward on Saturday September 08 2018, @07:15PM (#732282)

          I don't mind if you want to include Pluto in your definition of Planet, however you have to include Eris and any other similar objects as well.

          That's OK. If they meet the criteria for a "planet" then they should be called a "planet".

          We then just need a new term to define "big planets".

          Hmm ... why? What's the difference between a "planet" and a "big planet"? Why would we need to distinguish between them?

        • (Score: 2) by theluggage on Saturday September 08 2018, @08:29PM

          by theluggage (1797) on Saturday September 08 2018, @08:29PM (#732302)

          Both size and mass wise the jump between Pluto/Eris and Mercury is enormous

          Lets see - looks up some numbers on Wikipedia - I make Pluto 49% of the size of Mercury... and once you add in the larger moons there's severalin-between sized rocky balls in the solar system. On the other hand, Uranus a mere 44% of the size of Saturn and there is nothing in between. That's not to mention the fricking huge quantum leap in diameter and mass between Earth and Neptune... If exoplanet-detection technology improves so that Astronomers can be sure that they're not just picking up the oddities then either the gaps will get filled in or the real, physical distinctions will show up.

          however you have to include Eris and any other similar objects as well.

          Is anybody saying otherwise? Its the Pluto-demoters who argue against Eris etc. being planets.

    • (Score: 2, Informative) by Anonymous Coward on Saturday September 08 2018, @03:09PM

      by Anonymous Coward on Saturday September 08 2018, @03:09PM (#732215)

      Historically the term "planet" refered to the historical planets of Mercury, Venus, Mars, Jupiter and Saturn.

      The classical planets include the moon and the sun too.

    • (Score: 1, Offtopic) by Gaaark on Saturday September 08 2018, @03:24PM (1 child)

      by Gaaark (41) on Saturday September 08 2018, @03:24PM (#732223) Journal

      Playin' with "Muh muh muh myyy scrotum"!

      --
      --- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
      • (Score: 2) by Gaaark on Sunday September 09 2018, @02:55AM

        by Gaaark (41) on Sunday September 09 2018, @02:55AM (#732374) Journal

        Off topic?
        He's talking about balls, balls, balls, balls....

        What you got in YOUR scrotum?

        --
        --- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
    • (Score: 2) by requerdanos on Saturday September 08 2018, @04:11PM (5 children)

      by requerdanos (5997) Subscriber Badge on Saturday September 08 2018, @04:11PM (#732239) Journal

      The solar system has... Balls of rock orbiting other balls (the moon, ganymede, titan, etc)

      Well, your list of examples of balls orbiting other balls is missing some categories of things.

      Like...

      • The Sun (orbits the gravitational center near the ball of black hole or whatever at center of galaxy)
      • Mercury, Venus, Earth, Mars, Many ball-shaped asteroids, Jupiter, Saturn, Uranus, Neptune, Pluto (orbit gravitational center near the ball of gas at center of solar system)

      And while we're playing with definitions to see whether they hold up, how about, since these balls are orbiting the center of gravity of a system, that means that Pluto orbits Charon as much as Charon orbits Pluto, Earth orbits its Moon as much as its Moon orbits Earth, right? I mean, how do we even define that except for saying that the smaller orbits the larger? Even that isn't true, because each ball is orbiting the gravitational center of the two-body system, not the other ball irrespective of itself.

      • (Score: 2) by theluggage on Saturday September 08 2018, @07:58PM (4 children)

        by theluggage (1797) on Saturday September 08 2018, @07:58PM (#732289)

        I mean, how do we even define that except for saying that the smaller orbits the larger?

        "Smaller orbits the larger" seems like a perfectly cromulent and easily-defined standard. Obvious alternative would be to say that a "moon" is orbiting a "planet" if the barycentre of the two bodies was inside the planet, otherwise you have a binary planet... However, I think that makes Charon/Pluto a binary so that's another argument to contend with.

        • (Score: 3, Informative) by requerdanos on Saturday September 08 2018, @08:28PM (3 children)

          by requerdanos (5997) Subscriber Badge on Saturday September 08 2018, @08:28PM (#732300) Journal

          Obvious alternative would be to say that a "moon" is orbiting a "planet" if the barycentre of the two bodies was inside the planet, otherwise you have a binary planet...

          That sounds a lot more tenable than "smaller orbits larger," sure.

          otherwise you have a binary planet... However, I think that makes Charon/Pluto a binary so that's another argument to contend with.

          Heh, no, Charon/Pluto would be "binary biggish rocks" or "binary dwarf planet/smaller thingy combo" or "binary rock soup" but not a binary "planet" since, of course, Pluto is too small to qualify and Charon smaller still.

          The Pluto qualification people are dancing round here seems to be "Historically Identified As Totally A Planet By Ancients Long Dead If It Was Good Enough For Galileo Et. Al. Then Good Enough For All Time" which feels really nice (like "small orbits big") but feels does not make "is" when you are doing science.

          Early astronomers tried hard to figure out how the sun and other planets orbit the Earth here at the center of creation, but despite them being long dead, we don't try to enshrine their beliefs. Pluto's planethood should probably fall into that category as well.

          • (Score: 2) by theluggage on Sunday September 09 2018, @10:05AM (1 child)

            by theluggage (1797) on Sunday September 09 2018, @10:05AM (#732432)

            The Pluto qualification people are dancing round here seems to be "Historically Identified As Totally A Planet By Ancients Long Dead If It Was Good Enough For Galileo Et. Al. Then Good Enough For All Time"

            Only one side is dancing around that definition: I have not seen anyone here arguing that Pluto should be a "planet" but Eris and co. shouldn't. Rather, its the Pluto-demoters who are trying to contrive a pseudo-scientific justification for their (particular) take on tradition. The serious issue is here is not what we call Pluto, but the suggestion that the IAU has voted in wonky science to ensure that the "right people" get bragging rights for discovering planets .

            Its really a simple choice: (a) leave "planet" as a slightly ambiguous historical term (as it was before the IAU put their foot in the pie), or (b) come up with a valid formal definition that has genuine scientific significance (the "sphere" one being the best candidate so far except for the pesky reality of having to accept a few extra planets). I'd probably vote for (a): I'm not a fan of trying to retcon old words with new definitions (see: weight, work, food, vegetable...)

            • (Score: 2) by requerdanos on Sunday September 09 2018, @04:25PM

              by requerdanos (5997) Subscriber Badge on Sunday September 09 2018, @04:25PM (#732492) Journal

              I'd probably vote for (a): I'm not a fan of trying to retcon old words with new definitions

              To me, (b) is the more appealing because I would be excited to see bodies newly recognized as planets, and because I recognize that Eris, Ceres, et. al. wander just as much as Venus and Mars and so I could convince myself that the definition is simply become more precise as science advances.

              I had not thought of the Pluto-demoters in such a political/opinion based way until you pointed this out to me.

          • (Score: 4, Informative) by toddestan on Monday September 10 2018, @02:16AM

            by toddestan (4982) on Monday September 10 2018, @02:16AM (#732628)

            The Pluto qualification people are dancing round here seems to be "Historically Identified As Totally A Planet By Ancients Long Dead If It Was Good Enough For Galileo Et. Al. Then Good Enough For All Time" which feels really nice (like "small orbits big") but feels does not make "is" when you are doing science.

            Actually, most people seem to be arguing for the hydrostatic equilibrium definition, which is a consistent, clear-cut, and a very scientific definition of what is and is not a planet. And yes, we all know that means there are actually far more than 9 planets by that definition - I don't see anyone here arguing that that "planet" should include Pluto but not objects like Ceres.

            It's the people who have decided that there should only be eight planets in the solar system that are dancing around trying to create a definition that includes those eight objects and excludes all other objects. Of course, you can work backwards to create some arbitrary definition to do so for that works for the solar system, but you'll more than likely run into problems with other solar systems where things may not be so clear-cut. I mean, those objects orbiting other stars that Kepler keeps finding we have been calling planets, but that's a bit presumptuous because we can't actually know if they really are planets because we have no way to know if they have actually "cleared" their orbits - which just shows how poorly thought out the IAU definition is. But using hydrostatic equilibrium as the definition of a planet can be applied consistently everywhere, and with that definition there's no question those objects are planets. Of course, the IAU gets around that problem by defining a planet as something that only orbits our Sun, which is also ridiculous.

  • (Score: 2) by RS3 on Saturday September 08 2018, @01:00PM (3 children)

    by RS3 (6367) on Saturday September 08 2018, @01:00PM (#732175)

    I hear, respect, and empathize with your being tired of the "Pluto is a planet" crowd. I grew very weary of the "Pluto is not a planet" din and similarly wondered why anyone wastes time on such things. I also wondered why so many people even care. Fortunately for my own peace of mind, I'm no longer bothered by it and almost enjoy the show.

    It is human nature to classify all things, while definitions and classifications evolve and change. It may be painful to those of us who have a lighthearted interest in astronomy, but like anything, there are those who are passionate about it. Without passionate pursuits and endeavors, we would likely still dwell in caves.

    All that said, I'd much rather the time and mental effort be put into cancer research or something more productive for quality of life on earth, but I feel that way about much of society's time-wasters.

    • (Score: 2) by Immerman on Saturday September 08 2018, @02:37PM (2 children)

      by Immerman (3985) on Saturday September 08 2018, @02:37PM (#732199)

      Look at the bright side - if all that passion was directed to promoting human health we might have immortality by now - for that tiny portion of the species who could afford it because their greatly extended lifespans allowed them to accumulate 99.9% of the wealth, and why should they share their advantage?

      • (Score: 2) by requerdanos on Saturday September 08 2018, @04:13PM (1 child)

        by requerdanos (5997) Subscriber Badge on Saturday September 08 2018, @04:13PM (#732240) Journal

        if all that passion was directed to promoting human health we might have immortality by now

        I am not sure that passionate complaining (which simply consumes things, like patience) can actually be redirected into something that instead produces things (like immortality).

        • (Score: 2) by MostCynical on Saturday September 08 2018, @08:54PM

          by MostCynical (2589) on Saturday September 08 2018, @08:54PM (#732313) Journal

          But whinging on the web is forever [archive.org]

          --
          "I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex