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Space Earth NASA Science

A New Definition Would Add 102 Planets To Our Solar System -- Including Pluto (washingtonpost.com) 150

Posted by BeauHD from the didn't-last-long dept.
The Grim Reefer quotes a report from The Washington Post: Is Pluto a planet? It's not a question scientists ask in polite company. "It's like religion and politics," said Kirby Runyon, a planetary scientist at Johns Hopkins University. "People get worked up over it. I've gotten worked up over it." For years, astronomers, planetary scientists and other space researchers have fought about what to call the small, icy world at the edge of our solar system. Is it a planet, as scientists believed for nearly seven decades? Or must a planet be something bigger, something more dominant, as was decided by vote at the International Astronomical Union (IAU) in 2006? The issue can bring conversations to a screeching halt, or turn them into shouting matches. "Sometimes," Runyon said, "it's just easier not to bring it up." But Runyon will ignore his own advice this week when he attends the annual Lunar and Planetary Science Conference in Houston. In a giant exhibit hall crowded with his colleagues, he's attempting to reignite the debate about Pluto's status with an audacious new definition for planet -- one that includes not just Pluto, but several of its neighbors, objects in the asteroid belt, and a number of moons. By his count, 102 new planets could be added to our solar system under the new criteria. USA Today reports: "In the mind of the public, the word 'planet' carries a significance lacking in other words used to describe planetary bodies," the proposal states. "In the decade following the supposed 'demotion' of Pluto by the International Astronomical Union, many members of the public, in our experience, assume that alleged 'non-planets' cease to be interesting enough to warrant scientific exploration."
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A New Definition Would Add 102 Planets To Our Solar System -- Including Pluto More

A New Definition Would Add 102 Planets To Our Solar System -- Including Pluto

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  • Pluto isn't a planet! (Score:5, Funny)

    by Calydor ( 739835 ) on Wednesday March 22, 2017 @02:07AM (#54086397)

    He's a dog!

  • 102 planets?? (Score:1)

    by Anonymous Coward

    It's going to make calculating a horoscope very complex. The *only* way will be with computer software, and you'll need large-format plotters to print charts.

  • Better Idea (Score:2, Interesting)

    by Anonymous Coward

    How about this?

    Require hydrostatic equilibrium and that the object orbits the sun. That eliminates most asteroids and things like that. If two bodies are in hydrostatic equilibrium and the center of mass is outside of the center of either body (the Pluto-Charon system), it's a double planet. That seems logical to me. Unfortunately, the definition that's been proposed would include moons as planets, even though they clearly orbit a planet.

  • No (Score:2, Troll)

    by frovingslosh ( 582462 )
    No. Nothing can be a planet unless it is larger than Neil deGrasse Glactus's ego. A dwarf planet is no more a planet than a dwarf person is a person.

    • No. Nothing can be a planet unless it is larger than Neil deGrasse Glactus's ego. A dwarf planet is no more a planet than a dwarf person is a person.

      By that definition we live on a 'moon'.

      • Re: (Score:3)

        by Rei ( 128717 )

        Well, the current definition is "cleared the neighborhood" (despite how much that they like to pretend that it actually says "gravitationally dominant"). And Earth most definitely has not cleared its moon. So....

        Actually, by that definition, Earth isn't a moon, either, as it doesn't orbit something defined as a planet. Earth would be a "small solar system body".

  • because this shit definately doesn't matter.

  • Didn't Old Bill ask, "what's in a name? That which we call shit by any other name would stink as bad"

  • Need to lose some moons as well (Score:5, Interesting)

    by evanh ( 627108 ) on Wednesday March 22, 2017 @03:22AM (#54086513)

    Nothing should be called a moon if it doesn't have the gravity to produce plasticity in the rock.

  • Once a planet... (Score:3)

    by Hognoxious ( 631665 ) on Wednesday March 22, 2017 @03:35AM (#54086535) Homepage Journal

    ... always a planet.

  • Has anyone asked Pluto how it identifies itself? I bet none of you have checked your privilege and even thought of it!

  • obligatory (apocryphal) Bill Gates quote: (Score:5, Funny)

    by ctrl-alt-canc ( 977108 ) on Wednesday March 22, 2017 @04:59AM (#54086661)

    640k planets ought to be enough for anybody.

  • The term "planet" is arbitrary, whatever we define (Score:5, Informative)

    by Sique ( 173459 ) on Wednesday March 22, 2017 @05:04AM (#54086673) Homepage
    Originally, the planets (greek: wanderers) were those objects in the sky that didn't remain fixed in the stellar constellations, but actually wandered through them. Thus, Sun and Moon were considered planets too, and besides them, five other objects were constantly visible to the bare eye with no fixed place: Mercury, Venus, Mars, Jupiter and Saturn. And because they were seven, and seven was considered by the ancient cultures of the Mediterran to be a holy number, everything was fine. (Occasional comets which aren't constantly visible were thus considered shakeups of the celestial order and taken as bad omens.)

    And then Ptolemy's geocentric model put Sun and Moon in a special group, because differently than the other planets, they never change direction in the sky, which the others do. Thus, the trajectories of Sun and Moon were easy, while the other planets needed cycles and epicycles to describe. This was one of the reasons, Nicolaus Copernicus came up with the heliocentric model, because then it made sense why Sun and Moon were "circular" wanderers, while the other planets were "epicyclic" wanderers, So, Sun and Moon were no longer considered planets, a position already shaky in the Ptolemian model. But it added Earth as a new planet. Copernicus' system didn't come up with good predictions of the planetary positions though, thus it wasn't widely accepted and even considered heretic by the Catholic Church. Johannes Kepler improved on the predictive power of the Copernican system, but Ptolemy's model was so finely tuned by now that it still was preferred for practical reasons. Galileo Galilei's discovery of the Iovian Moons gave credibility to the Keplerian model, but for navigational and other purposes, Ptolemy was still more exact. And it created a new class of celestial bodies: Suddenly, there wasn't one Moon, there were several moons out there. From a classical point of view, all moons were planets too: no fixed positions within the stellar constellations. At the end of the 17th century, Isaac Newtons Theory of Gravity gave a better model, Ole Roemer's discovery of the Speed of Light added some clues, and finally, the heliocentric model was better at predicting planetary (and lunar) positions than Ptolemy. But then a flood of new discoveries of celestial bodies clouded the view again: Uranus, Ceres and finally Neptune were discovered, and then all the other asteroids circling the Sun between Mars and Jupiter. Somehow the size of the Earth moon was used as a cut-off: Everything larger than the Moon circling the Sun was considered a planet, everything else an asteroid (which literally means "star like"). It was as arbitrary as anything else, but the Moon was close by and well studied, so for practical purposes, it made sense.

    When Pluto was discovered, it became planetary status, because at first, its size could not be determined from direct observation, only because of the brightness (15 mag), it was at first considered to be Earth sized. So it got the planetary status. Later there were better pictures with larger resolution, and the estimated size shrank down to ~2500 km in diameter, and in the same way, the estimated reflectiveness (albedo) increased, so in the 1980ies, Pluto was considered a "dirty snowball", consisting mainly of water ice mixed with planetary rock. Thus the cut-off point "Moon size" was crossed, and doubts about Pluto's nature as a planet arised. It was speculated that it was a former Neptune moon losing its orbit. And when the next transneptunian objects were discovered, like Eris, with about the same size than Pluto, the whole "what is a planet" question became virulent. Simple enumeration as in "The planets are those nine celestial objects we call Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune and Pluto" didn't work anymore, and a meaningful definition which included Pluto, but not too many other newly discovered objects, wasn't readily available.

    • We keep trying to come up with rules which include those objects want to include and exclude all the others. The rules are arbitrary too, the result of a majority vote by some group. This is not science; it is semantics.

  • "...have fought about what to call the small, icy world at the edge of our solar system."

    I have a name for it.

    Irrelevant.

    Not good enough? Need more clarity? OK, here's some more.

    Uninhabitable. Worthless. Pointless.

    Until we start landing space mining equipment there to bring back an argument of value, perhaps we could find something else to discuss. This "religious" discussion is reduced to nothing more than textbook revenue when they need to re-write millions of them, which makes it rather cheap and not very scientific.

    • Re: (Score:2)

      by Calydor ( 739835 )

      Let's see you call it worthless and pointless after it acts as a physical shield against a comet that would have otherwise come straight for Earth.

      • Let's see you call it worthless and pointless after it acts as a physical shield against a comet that would have otherwise come straight for Earth.

        And Pluto could act as a billiard ball and cause a comet that would have otherwise not been in our trajectory to be manipulated to our demise. Fate is sometimes a fickle bitch.

        I was being facetious with certain labels to highlight the fact that the label argument itself is both worthless and pointless. Scientific minds could be used for discussions far more relevant than textbook revenue.

  • Interesting comment from last time (Score:5, Informative)

    by RCourtney ( 973307 ) on Wednesday March 22, 2017 @07:27AM (#54087109)
    The last time this was discussed on slashdot there was a very interesting series of comment posted by Rei [slashdot.org] that shed a lot of light on what the issues surrounding this are and how the situation (and redefining what a planet is) came to be.
  • (you should know the music [99-bottles-of-beer.net]...)

    9 planets orbiting around the Sun. 9 planets.
    Take Pluto down, pass it around, 8 planets orbiting around the Sun...

  • Buried the Lead (Score:5, Informative)

    by PMuse ( 320639 ) on Wednesday March 22, 2017 @07:54AM (#54087219)

    The proposed definition can be found at words 765-799 of the article.

    A planet, he says, is anything massive enough that gravity pulls it into a sphere (a characteristic called “hydrostatic equilibrium"), but not so massive that it starts to undergo nuclear fusion and become a star.

    The preceding 764 words are a useless regurgitation of how people feel about definitions in general and Pluto in particular. Spare me.

    • The Earth only has enough gravity to pull it into an ellipsoid, not a sphere. Also, is asteroid Ceres a "plant"? Kids will need to start inserting new names between Earth and Mars.

  • Use a liberal definition of planet (Score:3)

    by Rolgar ( 556636 ) on Wednesday March 22, 2017 @08:04AM (#54087275)

    I like the definition of planet based upon any body of sufficient mass to be round (or nearly so to some mathematical measurement). That is, it is a planet based on size/mass and what it is within itself, and it is what it is no matter where it is (in the inner solar system or floating between stars).

    The definition of having cleared it's neighborhood means that when it first formed, Jupiter wasn't a planet because it hadn't had time to clear it's neighborhood, and obviously this would include all of the other planets during formation. At some point, we'll probably find a distant solar system where there are two planets that orbit each other. Since they wouldn't have cleared their orbit of their twin, could they even be considered a planet under the 2006 definition even if they were far more massive than Earth, and even had an earth like eco-system? Would you like to be the astronomer that had to be pedantic an tell journalists that these weren't planets because it's hadn't eliminated it's binary partner?

    So, moons (not counting Mars', perhaps they would be called asteroid moons) are planets (or planetoids) that orbit larger planet. If you want to have a distinction for planets that do what the re-definition did in 2006, add some modifier like solar planet (indicating that the planet is considered to be a part of a star's main planetary system) and give it the additional requirements that were voted on 2006.

    • I like the definition of planet based upon any body of sufficient mass to be round (or nearly so to some mathematical measurement).

      I prefer this method too- but the level of deviation it has from a perfect sphere before it can be considered a planet would probably be arbitrary... no planet is perfectly spherical.

  • My Very Excellent Mother Just Served Us Noodles with a side of broccoli, but my younger brother did not like to eat his broccoli so he decided to have pizza instead going to the pizza place around the corner asking toni if he offered pizza with tuna to which tony replied that he...

  • Comment removed based on user account deletion

  • People should stop whining about semantics or personifying a planetary body as if it was a person. smh

  • "Planet" and "moon" should be declared lay terms with no scientific or technical meaning. All non-stellar bodies are "satellites" which are referenced to their gravitational primary. Earth is a "solar satellite". Phobos is a "Martian satellite". Pluto is a "solar satellite", as is Ceres, Vesta, Jupiter, etc. Dactyl is an "Idanian satellite", which is in turn a "solar satellite". If you just want to get size involved then reference other known quantities. Pluto is a ".177 Lunar mass solar satellite", Jupiter

  • Lets simplify this... (Score:5, Interesting)

    by xession ( 4241115 ) on Wednesday March 22, 2017 @09:45AM (#54087831)
    A planet is any object in orbit around a star, of sufficient mass to reach hydrostatic equilibrium, has not reached critical mass to achieve stellar fusion, and is the most prominent body in its orbit and neighborhood. That definition is going to add a few more planets but not many.

    The suggested definition from TFA is just as terribly obtuse as the 2006 definition. Even worse is the suggestion to change the word 'planet' to become an all encompassing term that now also means most smaller bodies as well (but not all). It makes things unnecessarily confusing. This just seems tantamount to two-year-old logic where one word now means everything.

    And look, my suggested definition expands.

    A moon is any object in orbit around a planet, of sufficient mass to reach hydrostatic equilibrium, and is the most prominent body in its orbit and neighborhood.

    A moonroid (haha maybe?) is any object in orbit around a planet, has not reached critical mass to achieve hydrostatic equilibrium, and is shares its orbit and neighborhood with other objects of similar mass.

    An asteroid is any object in orbit around a star, has not reached critical mass to achieve hydrostatic equilibrium, and is shares its orbit and neighborhood with other objects of similar mass.

    And so on. The hydrostatic equilibrium is critical to defining celestial bodies but it shouldn't be the only requirement to define a planet.

    • Re: (Score:2)

      by Rolgar ( 556636 )

      I think that size is sufficient as a beginning point. Linguistically, you want your word to do one thing to keep things simple. Classify all items by size as asteroids or planets. Where they are, the type of orbit (or lack of one), what they are made of should be a qualifier. Otherwise you have to have a different word for a planet based on where you find it. Orbiting a star = planet, orbiting a planet=moon, beyond the Neptune or not having a clear neighborhood=more classifications and words than we can cur

      • I'm all for adding modifiers but we have to think broadly yet precisely when defining what exactly makes a 'planet', a 'planet'. What is the cutoff in such a definition? I mean you can say its when they reach a certain circumference or when they reach hydrostatic equilibrium but then whats the upper limit? White dwarfs are certainly stars but can be close in size to the Earth. Just going by size makes it difficult to not define it simply as a planet. Or are all stars planets as well in this scenario?

    • Re: (Score:2)

      by PMuse ( 320639 )

      A planet is any object in orbit around a star, of sufficient mass to reach hydrostatic equilibrium, has not reached critical mass to achieve stellar fusion, and is the most prominent body in its orbit and neighborhood.

      A moon is any object in orbit around a planet, of sufficient mass to reach hydrostatic equilibrium, and is the most prominent body in its orbit and neighborhood.

      An asteroid is any object in orbit around a star, has not reached critical mass to achieve hydrostatic equilibrium, and is shares its orbit and neighborhood with other objects of similar mass.

      What does 'prominence in its orbit and neighborhood' gain us with respect to making the word usable in discussions?

      If we drop that criterion, it seems quite wieldy to me to discuss, for instance, binary planets or sibling planets when multiple bodies of sufficient size occupy an orbit. In the same way, we discuss Shilshole Bay and Elliott Bay as two bays in the same neighborhood rather than claim that they aren't bays because they are too close to each other.

      Keeping it requires us to say that bodies that l

      • binary planets or sibling planets when multiple bodies of sufficient size occupy an orbit.

        The Saturn moon Titan, is larger than planet Mercury and yet I've never heard anyone demand that Mercury be demoted or that Titan be promoted. One object will always take prominence, having the most mass in a system, even if the next largest object is somewhat close in size as well; it would still be a moon. I would argue the Earth-Moon system is very similar in its binary nature to Pluto-Charon, though at differing levels. No one is demanding that the Moon be called a planet.

        As for your example of bays,

        • Re: (Score:2)

          by PMuse ( 320639 )

          Thanks for the informative response. A couple of thoughts:

          As for your example of bays, your logic is faulty. Both can be bays in that circumstance, just like two objects can be moons of the same system, to which both bays are a part of a larger system known as Puget Sound.

          So, Shilshole and Elliott can both be "bays", but when it comes to Pluto-Charon (or any system with 2+ self-rounding bodies) only one of them is a "planet"? Hmmm.

          At this point, we could consume some time exploring Fishing Bay on the Chesapeake, but I think we'd soon conclude that terms like bay, sea, etc. have been applied pretty loosely and might themselves benefit from a debated and voted definition. My point, though, was this: we want the defin

    • Re: (Score:2)

      by Eloking ( 877834 )

      A planet is any object in orbit around a star, of sufficient mass to reach hydrostatic equilibrium, has not reached critical mass to achieve stellar fusion, and is the most prominent body in its orbit and neighborhood. That definition is going to add a few more planets but not many.

      The suggested definition from TFA is just as terribly obtuse as the 2006 definition. Even worse is the suggestion to change the word 'planet' to become an all encompassing term that now also means most smaller bodies as well (but not all). It makes things unnecessarily confusing. This just seems tantamount to two-year-old logic where one word now means everything.

      And look, my suggested definition expands.

      A moon is any object in orbit around a planet, of sufficient mass to reach hydrostatic equilibrium, and is the most prominent body in its orbit and neighborhood.

      A moonroid (haha maybe?) is any object in orbit around a planet, has not reached critical mass to achieve hydrostatic equilibrium, and is shares its orbit and neighborhood with other objects of similar mass.

      An asteroid is any object in orbit around a star, has not reached critical mass to achieve hydrostatic equilibrium, and is shares its orbit and neighborhood with other objects of similar mass.

      And so on. The hydrostatic equilibrium is critical to defining celestial bodies but it shouldn't be the only requirement to define a planet.

      Hmm mostly how I see it but it fail to address binary system like Pluto–Charon.

      In my mind, Charon shouldn't be considered a satellite to Pluto since the centre of orbit is outside of Pluto. Neither are "Moon", both are "Planet".

      As for how to separate asteroid to "Planet", hydrostatic equilibrium is a clear win. But in my mind planet shoudl be separated in 3 group :

      - Asteroid : No hydrostatic equilibrium (No rounded shape)
      - Dwarf Planet : No Atmosphere (rounded shape)
      - Planet : Atmosphere
      - Gas Giant :

      • In my mind, Charon shouldn't be considered a satellite to Pluto since the centre of orbit is outside of Pluto. Neither are "Moon", both are "Planet".

        Difference of opinions here I guess but the definition I offered clarifies that the object to be considered a planet in any sort of clustered central orbiting system, has to be the most prominent body in that orbit. That would make Pluto the planet, and Charon the moon. Charon is about half the size of Pluto, so there is a significant difference on the gravitational influence of each celestial body as well.

        The Earths moon is roughly a quarter size of our planet and in many respects, we share similaritie

        • Re: (Score:2)

          by Eloking ( 877834 )

          Difference of opinions here I guess but the definition I offered clarifies that the object to be considered a planet in any sort of clustered central orbiting system, has to be the most prominent body in that orbit. That would make Pluto the planet, and Charon the moon. Charon is about half the size of Pluto, so there is a significant difference on the gravitational influence of each celestial body as well.

          The Earths moon is roughly a quarter size of our planet and in many respects, we share similarities to the Pluto-Charon system. I would argue that the Earth-Moon system is also a binary system too. However, the most prominent body of influence should retain the most prominent hierarchical name. Hence, the Earth is a planet, Luna is a moon, Pluto is a planet, and Charon is a moon.

          Yeah I understand what you mean. And I understand that Charon kinda feel like a moon. But what if both (Charon and Pluto) were about the same size? You'll say that the one slightly bigger is the planet and the one slightly smaller the moon?

          In my mind, for a Moon to be considered a "Moon", it have to be greatly smaller than it's planet. That's why I love to use the centre of orbit (or Barycenter) as a reference. If a "planet" is massive enough so it's clearly the "Master" of it's own system, then the barycen

  • At least try a more promising way to make Pluto a planet again. Why would anyone want to have 200 planets?
  • I remember always thinking that Pluto was odd as a planet. In elementary school they'd explain how all of the planets orbited along the ecliptic plane, and keep to their own orbits, except for Pluto. Its orbit isn't on the same plane as the other planets, and it crosses into Neptune's orbit. For me, that's what makes it not a planet.

  • "I was big enough for your mom." -- Pluto

  • Everyone knows the song "my very educated mother just served us nine pizza pies" Adding 102 planets would be impossible for kids to remember LOL.

  • Pluto was well established as a planet years ago in the irrefutable context of song.

    Pluto- 2 Skinnee Js: http://youtu.be/heRn5n6z-Ck [youtu.be]

  • From the article, musing about how an alien visitor might classify them...

    "Which of these would they consider a “planet” — or whatever the alien term for “planet” might be?"

    Maybe a more useful classification would be to classify them by the characteristics of the body itself, irrespective of its orbit. Their word that we'd likely translate as "planet" might only apply to Venus, Earth, Mars, and Titan. (Rocky bodies with significant atmosphere.)

  • Most of the arguments for 102 extra planets in our solar system seem to be based on the public being excited about having a planet. I don't think it'd work that way. Having 110 planets would water the concept down. The problem is that an object is perceived as less interesting because of it, and that's not true at all.

    There's nothing to stop a moon from being as large and complex as any planet. Ceres is categorized as a dwarf planet, and it's got surprising geology, even a chance of harboring water and

  • I'm a linguist, and I don't understand this controversy. Why should anyone care how the IAU defines 'planet'? They can't keep you from using the word any way you want, and their definition obviously makes no difference whatsoever to Pluto itself, nor does it have any legal standing (you won't lose your health care depending on which way they define it). So what's the big deal?

  • That 2006 vote came when most of the scientists had packed up and gone home. So the vote wasn't really a vote. They shouldn't have voted in the first place. After the uproar the should have admitted they made a mistake. From what we know about Pluto, it should be classified as a planet. They should admit it was a mistake.

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