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Education

NASA's Pluto Mission Seeks to Confuse People

By Keith Cowing
NASA Watch
January 20, 2015
Filed under ,

NASA Spacecraft Get a Closer Look at Dwarf Planets Pluto and Ceres, NY Times
“Marc W. Buie, a planetary scientist at the Southwest Research Institute in Boulder, Colo., and a member of the New Horizons team, agrees with Dr. Stern but wishes the issue would go away. Years ago, people would be fascinated to hear the scientific puzzles about Pluto. Now, conversations usually start with “Is Pluto a planet?” “It’s a very annoying, distracting issue,” Dr. Buie said. “You have to get past this wall of this nonscientific issue before you get to the good things.”

“The moon is such a planet I can’t even stand it,” [Fashion designer] Mizrahi says, exasperated. “Well, what else is it if it’s not a planet?” Under Dr. Stern’s definition, Mr. Mizrahi would win the argument. “I am happy to defend him,” Dr. Stern said via email Sunday. “I see no logical reason why large moons that are in hydrostatic equilibrium should not be considered planets too, and I call them that.” Dr. Stern’s classification system distinguishes moons as “secondary planets,” while “primary planets” directly orbit around the sun — pushing the number of planets in the solar system to more than 20.”
Keith’s note: So … let’s see if I understand the New Horizons mission’s revised solar system nomenclature: Planets orbit the sun. Planets also orbit other Planets. Moons orbit Planets but Moons do not orbit the sun otherwise they’d be Planets which also orbit Planets and the sun. But wait – there’s more: now we need to add Primary Planets and Secondary Planets into the mix. So when does a Moon become a Secondary Planet? Is it still a Moon also? Can Planets be Moons and Moons be Planets?
Iapetus is not in hydrostatic equilibrium so it is not a Planet (right?). But it is a Moon (right?). But Iapetus is larger than Ceres which is .. a Planet (right?) Pluto’s Moon Charon is smaller than Iapetus but Pluto fans refer to it as a Planet. Alas, Pluto fans always love to use the “Titan is larger than Mercury” argument to justify Titan as a Planet.
I can’t wait to see how all NASA education materials are adjusted for the New Horizons mission so as to tackle this issue. Textbooks will clearly need to be revised to reflect NASA’s latest discoveries. Who determines how these revisions will be made? Will other missions be required to adapt accordingly or is NASA going to be talking about more than one system of planetary nomenclature? What will happen at press events – will NASA be required to issue press releases in both nomenclatures (as well as English/metric)? WiIl this IAU Vs Pluto fans thing just drag on and on?
The oddest thing of all is how the Pluto fans rant about how some small group of people at IAU made this decision about what a Planet is without consulting everyone else – yet the Pluto fans have gone out and proclaimed this new nomenclature for Planets and Moons without consulting anyone else. Pot-Kettle-Back.
Why make things more complex? Our solar system has lots of worlds. Ice worlds. Rock worlds. Gas worlds. Some worlds are big others are small. Some worlds orbit the sun and are “planets”. Some worlds orbit planets and are called “moons”. This simply defines the location of a world – not its inherent physical nature. #OcamsRazor

NASA Watch founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.

28 responses to “NASA's Pluto Mission Seeks to Confuse People”

  1. Yale S says:
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    All moons do orbit the Sun. A planet and its moon(s) orbit each other around a common center of mass (the barycenter), like the middle of a barbell, which is what orbits the Sun.
    Now, this barycenter (due to the major difference in masses) usually lies (way – near the center) beneath the surface of the “planet”, which thus makes the lighter objects moons.

    Saturn is 72,000 miles in diameter. The barycenter of the Titan-Saturn system is only 175 miles from the center of Saturn.
    Titan (and Pandora) are huge interesting worlds with thick atmospheres, but they are moons.

    But consider our Earth-Moon system. It has often been called a Double Planet. The Earth has a diameter of 8K miles and the Moon is 2K, with a difference in masses of only 80 to 1 (much closer than any other official planet). The barycenter is currently within the Earth about 3/4 of the way up from the center to the surface, but in the future it will be located between the Earth and Moon. Then, in that distant time, will the Moon still a “moon”?
    Right now Pluto and Charon have their barycenter in space between them. They differ in mass by only 8 to 1.
    If Charon is spherical, etc, and Pluto is considered a planet then it really is a double planet.
    As an aside, when the planets all line up on one side of the sun (like in 2023) the solar system barycenter will be outside of the Sun!

  2. Jackalope3000 says:
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    “You have to get past this wall of this nonscientific issue before you get to the good things.”

    Pluto’s classification IS a scientific issue. Part of science is about classifying things. Another key element of science is that ideas are subject to revision when new data becomes available.

  3. RocketScientist327 says:
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    Pluto is a planet… walaah

    • Yale S says:
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      I am rich, famous, and Greek God-like good-looking, Voilà
      Dang…
      Well sometimes the magic works, and sometimes it doesn’t.
      -Old Lodge Skins (from Little Big Man)

  4. QBand says:
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    Well, we should not underestimate students. If they are “confused”, they might seek out more information and build themselves a better and broader view of the Solar System than just by memorizing some silly letter/word combinations and only studying it because of studying.

    It is clear that Solar System is only made of Sun+Jupiter+”some small junk” if you look any closer.
    If you look just planets, it is only Jupiter+Saturn+small junk.
    If you consider asteroid belt, it is Ceres & the rest.

    So, perspective is important but also deceitful.

    It will always remain a bit uncertain for us how to categorize our own Solar System, especially in the future when we get more information of the other solar systems in the universe around other stars. And they most likely will be even more bizarre and controversial than ours.

    No matter what, I think everyone can agree however, that with our current knowledge, it is obvious that there are 8 objects that clearly stand out and form their own group, “Planets”. There are the 4 inner rocky planets, and 4 outer gas giants. There can be no serious argue against that. It is the underlying truth.

    Almost as clear definition is the one that there is a certain region of small rocky objects between Mars and Jupiter, the Asteroid Belt.
    Again, there is another region of similar small icy objects beyond Neptune. Mainstream media calls it the Kuiper Belt, but it also includes Scattered Disc and even further out the still hypothetical Oort Cloud.

    Ok, let’s stop now.

    I think most of us can agree with these facts, right?
    There is nothing confusing here. No confused students, no textbooks to be burn in the town square. A Solar System we all can believe and makes sense. And is real. And will be.

    And all this shows how interesting and varied universe there is around us and in our astronomical backyard.

    So, let’s move on. Biggest and clearly the dominant object of this first region is Ceres. Yes, Ceres and period. You may call it what you want but it is Ceres, interesting world and sits there. No confused students.

    The other region has many dominant objects with similar sizes, Pluto, Eris, Haumea, Makemake etc. They are fascinating objects. Yes they are. Call it what you want, they remain so. They are definitely not same category objects as the “8 big ones”. No doubt. They have different composition, history and surroundings. But they are not planets. They are something else. Again, no confused students.

    What is the problem here?
    Main stream media’s patience of a 3-year old when it comes to science issues or getting “scandal” headlines and click count rocketing to skies?

    Once you sit down, explore some serious scientific sources and think, you get this far, and realize how silly and really unimportant issue is something like “yes but pluto must remain a planet because…”. Pluto is not a planet and it should have never been. Get. Over. It.

    If you want to categorize it, please do. But don’t put it where it does not belong. Same goes with Eris. And Ceres (it had the same destiny already back in the 1800s). And Titan. And other moons. And other non-planets. Because now there is not anymore The 8 Planets & Pluto in our knowledge, but The 8 Planets & vast region of smaller icy objects.

    But think about the children!
    Won’t please somebody think about the children!?!

    Yes. Think about them. Let them learn. And let them be spared from these silly fights about demotion, emotion and pseudo-sciences of our time…

    • Yale S says:
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      I would generally agree, but I think I would upgrade the larger moons, which appear to be genuine offspring of the big planets and dominated by them, into a hard classification: moons.

      • QBand says:
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        In this wiki-page the pie charts for masses are really an eye-opener and a good starting point for seeing what is what in our Solar System:
        http://en.wikipedia.org/wik

        And yes, yales, as well as there are the Big 8 of planets, there’s also a very clear bunch of Big 7 of moons.

        • Yale S says:
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          Ganymede is a pretty serious moon. I vote for propelling it out of Jovian space (its too rad there anyway) and move it where its warmer and can be a real planet.

    • Citizen Ken says:
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      I’ve found a modified Toilet Paper Solar System exercise to be quite useful. Basically the various bodies are scaled onto a 300-sheet roll of toilet paper. Find a really long hallway and have the students lay out the cards I have for the various bodies.

      What quickly becomes evident is that the terrestrial bodies are all clustered close in, there’s an asteroid (some with their own ‘moons’) belt, and then the gas giants are the suburbs of the Solar system. Pluto is all the way out in the boondocks, joined by Sedna, Eris, Haumea, Makemake, Quaoar and others.

      When it’s laid out this way, the students can easily grasp the nature of our Solar system, and why the new classification is the way it is. Besides, who wants to figure out a mnemonic for MVEMCJSUNPESHMQ…

      • kcowing says:
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        That’s certainly an interesting way to do this. Here in DC there is an exhibit that uses the National Mall to show the solar system scale. But in terms of the whole moon-planet thing that the Pluto fans are pushing, if they cannot simply define all of this in a book there is something wrong with their classification system.

    • laurele says:
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      “I think most of us can agree with these facts, right?”

      No, we cannot agree on this.

      There are no eight objects that stand out and form their own group. In what way do Earth and Jupiter stand out as similar and belonging to the same class? Earth has more in common with Pluto than it does with Jupiter. Both Earth and Pluto have large moons formed via giant impact; both have nitrogen in their atmospheres; both have rocky surfaces on which rovers and landers can land; both are geologically differentiated into core, mantle, and crust. In contrast, Jupiter is gaseous and has a composition like that of the Sun, solely hydrogen and helium. It has no solid surface and has its own “mini-solar system” of rings and moons.

      The architecture of the solar system can more accurately be viewed this way: there are three classes of planets–terrestrial, jovian, and dwarf. Terrestrials are rocky and big; jovians are gaseous; dwarf planets are much like terrestrials but smaller and do not gravitationally dominate their orbits. Satellites of planets that are spherical are compositionally and structurally akin to the terrestrial planets. They can be considered secondary or satellite planets. Moon is simply a synonym for satellite. Objects too small to be in hydrostatic equilibrium, such as asteroids, comets, centaurs, and KBOs can be considered Small Solar System Bodies. Objects nearly in hydrostatic equilibrium that have geology and layering such as Vesta and Pallas deserve their own category, possibly called “protoplanets,” a category between Small Solar System Bodies and dwarf planets.

      Arrogantly stating that “all can agree” with your position, which turns out to be one side in an ongoing debate, a position that places an object’s location first and foremost by making planethood contingent on orbital dominance is incredibly presumptuous. No, we cannot all believe in your solar system in which gravitational dominance is a condition for an object being a planet. Many people who study the solar system and constantly seek additional information cannot agree to put location ahead of an object’s intrinsic properties when it comes to definition.

      If this debate is such pseudoscience, why was the IAU so dead set on addressing it knowing probes to Pluto and Ceres were on their way and would provide unprecedented data that would help us understand and therefore classify these objects?

      Kids should not be forced to learn that something is “true” in science because an “authority” dictates it. They should be presented with the data and the various arguments and given the chance to actually think and draw their own conclusions.
      Pluto, Eris, and Ceres belong in a particular subclass of planets. Earth and Jupiter each belong in other subclasses, but all are planets; based on their composition and intrinsic properties, all DO belong in the same broad parent category, just as whales, bats humans, dogs, and elephants all belong in the broad mammal category.
      There is nothing wrong with open debate in science. What is wrong is opening a discussion and then arbitrarily declaring case closed for eternity when one side gets their way. Definitions will continually change as we discover more objects. For example, the presence of rogue planets means we can no longer require an object to orbit a star to be considered a planet.
      No one should “Get Over” a bad decision just because one partisan group of people want them to, even if that group considers themselves an “authority.” There are no eight planets and vast regions of smaller, icy objects because that classification system ignores the fact that some of the object s in these vast regions are small planets with all the same properties of their larger counterparts.
      How about sparing children from dogma and dictatorship by self-appointed “ruling elites?” The debate over dwarf planets’ status is not over, but the Dark Ages are.

      • kcowing says:
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        Hooray. The official New Horizons propagandist has arrived. Too bad you did not even bother to address the substance of the post. Instead you decided to rant on and on in circles about whatever. No one is debating that there are lots of different things in our solar system. Instead, the post focuses on the confusing Planet/Moon nomenclature that the NASA New Horizons mission is promoting – a nomenclature that no one has voted to adopt – including NASA. You Pluto Fans complain about the IAU process and then you go off and do exactly the same thing. Pot-Kettle-Black.

        • laurele says:
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          The New Horizons mission is not promoting any nomenclature system. Dr. Stern is. The mission is addressing only the object it is studying, Pluto.
          Putting an opinion or interpretation out there does not equate to adopting it. Dr. Stern is simply putting an idea into the discussion. Other people can put in other ideas. No one has to accept any of them. If Stern’s doing so promotes additional discussion, that is a good thing.

          I do not work for New Horizons in any official capacity. My views are my own; they are shared by some planetary scientists, and all I want is for them to be on the table with as much legitimacy as the IAU position.

  5. dogstar29 says:
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    Planets, dwarf planets, asteroids, comets and dust orbit the sun. Moons orbit planets, dwarf planets, or asteroids. Gravitationally bound groups of similar size like Pluto-Charon and many asteroids are named for the largest object, with the others referred to as moons. TMK there are no moons orbiting moons or planets orbiting planets.

  6. Steven Rappolee says:
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    “All these worlds are yours except Europa…………”
    Stern is right wrong word though.All objects large enough for gravity to shape them into spheres shall henceforth be called “Worlds”

  7. Paul451 says:
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    We really need some Vulcan’s to sort this while mess out. How’s NASA coming along with that warp drive?

    Seriously, it probably makes sense to split the size-of-the-object from the nature-of-the-object from the action-of-the-object, three classification systems with dissimilar nomenclature. Qband’s very elegantly described regions make a nice fourth classification.

    What amuses me, if you look at mass on a log scale, Pluto is not even a “Dwarf”, it’s much lower down. (Ceres is worse.) There are relatively clear clusters, the gas giants, then Earth/Venus, then Mars/Mercury, then Ganymede to Europa, then Triton/Eris/Pluto. Pluto is in the fifth or sixth group, and is the smallest member of even that group.

    https://upload.wikimedia.or

    It’s hard to see any consistent useful classification system that would describe Pluto as a planet. It’s 17th. It’s never going to be more than that. The more TNOs we discover, the more likely it will slip further down.

  8. laurele says:
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    The concept of primary and secondary planets was actually first considered in the mid-19th century, so it is hardly new.

    There are so many things wrong with this article that it is hard to know where to begin. You accuse NASA’s New Horizons mission of deliberately trying to confuse people.

    First, you fail to acknowledge that Dr. Stern is stating his professional opinion, which is not in any way an “official” position on the part of the New Horizons mission. That mission is comprised of leading scholars in the field of planetary science, each of whom has his or her individual professional view regarding planetary classification systems.

    New Horizons is a mission to Pluto. Its members have studied Pluto for many years and continue to do so. Who more than the first group to actually send a probe to Pluto is in a better position to discuss what Pluto is and how it should be classified? The majority of the IAU are not planetary scientists but other types of astronomers. The majority of the 424 (out of 10,000 members) who voted in 2006 are not planetary scientists. The majority of the 333 who voted that dwarf planets should not be considered a subclass of planets are not planetary scientists. And none of them is actually sending a probe to Pluto. Arguing that their view should take precedence over that of people who have studied Pluto and planets all their lives makes little sense.

    Stern’s individual viewpoint is based on the geophysical planet definition, which defines celestial objects first and foremost by their intrinsic properties rather than by their location. According to this definition, a planet is any non-self-luminous spheroidal body orbiting a star, free floating in space, or even orbiting another planet. If an object is large enough and massive enough to be squeezed into a round shape by its own gravity, it is a type of planet. This is similar to the classification in which any celestial object massive enough and large enough to generate nuclear fusion in its core is a type of star.

    Within the overarching class of star, there are many subcategories, as expressed via the Herzsprung-Russell Diagram. Why not have a similar classification system for planets taking into account multiple factors such as location, orbit, composition, etc.?

    Objects like Titan and Europa are intrinsically very akin to the terrestrial planets. They are rounded by their own gravity, a state known as hydrostatic equilibrium. Many have geology and layering. Some, like Titan, have atmospheres. Some of these moons are the top potential locations for extra-terrestrial microbial life in our solar system. Many of these are also ideal contenders for colonization once we develop the technology to expand beyond Earth into the solar system.

    The usage of terms like moon and planet changes over time based on new discoveries. The word moon specifically referred to Earth’s satellite only. When Galileo first discovered Jupiter’s satellites, he referred to them as four planets circling Jupiter. Soon, the term moon became a synonym for satellite–which one could argue it still is.

    Stars can orbit other stars. Galaxies can orbit other galaxies. And yes, planets can orbit other planets, as in the case of Pluto and Charon.

    So why can’t bodies like Europa, that have all the same characteristics as planets except for the fact they orbit other planets rather than the Sun directly be considered secondary or satellite planets? That takes into account both their intrinsic properties and their location.

    And what about giant extra-solar objects that don’t orbit any star but float freely in space? These are now known as rogue planets. Would you say they should not be considered planets because they don’t orbit a star?

    This really is not difficult. You are making it sound more confusing than it is. Hydrostatic equilibrium is a key physical property in celestial objects. An object may be bigger than another object, such as Iapetus being bigger than Ceres, but if it is not in hydrostatic equilibrium, it does not have the complexity and processes present in objects that are in this state. The defining issue is not size, but a physical property.

    Textbooks should talk about more than one system of planetary nomenclature, and some already do. They will continually have to be revised given the constant, rapid number of discoveries being made in our solar system and others. If textbooks have a problem keeping up, there always are online resources that can be utilized.
    As for the debate “dragging on,” there is nothing wrong with that. Issues are constantly revisited and reconsidered in light of new information. This is what scientists do.

    “Pluto fans,” who are really supporters of a geophysical planet definition, are putting this view out to the public as an option, not mandating it by decree as the IAU did. That is the group who made a decision and refuse to consult anyone else, even experts in the planetary field, and also refuse to ever revisit the issue.

    Science is by nature complex. You seem to want the simplicity of dogma.

    Our solar system has many types of objects, with the largest class being the broad category known as planets. Within that category, there are many types of planets in many different locations. The most important defining characteristic is not where an object is but what it is. It really is not as complicated as you seem to want it to be.

    • kcowing says:
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      Are you saying that the New York Times made mistakes? Where are the mistakes? Have you submitted a letter to the editor? Who appointed the New Horizons team to decide planetary nomenclature conventions? From your comments they are self-appointed – and yet you Pluto Fans rant and rave until you are blue in the face about how some small cabal at IAU committed a travesty by passing a planet/moon classification system you do not like – yet its OK if a few people – starting with a NASA mission PI – just decide how a NASA mission is going to refer to various bodies. Goofy.

    • Hug Doug ✓ᵛᵉʳᶦᶠᶦᵉᵈ says:
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      The Earth has places that are self-lumious. maybe it is a star? http://www.nhm.ac.uk/resour

  9. laurele says:
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    Mizrahi and the QVC incident really do not belong in the same discussion as the professional position of NASA scientists. That incident was an unfortunate display of how ill informed many of the American people are. No scientist would refer to the Moon as a star. This is just one of many misconceptions in a public who unfortunately know more about the Kardashians than about the real stars in the sky.

  10. Maurizio Morabito says:
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    I hereby declare there be only 8 galaxies! Know what, how can students cope with having to deal with the 20 galaxies that populate the cosmos?

    I hereby declare no one be burdened with having to remember the names of more than 8 people!

    REMEMBER THE GOAL OF SCIENCE ISN’T TO UNDERSTAND THE UNIVERSE, IT’S TO NOT CONFUSE PEOPLE WITH DEFINITIONS THAT NEED MORE THAN EIGHT WORDS TO BE EXPLAINED!

  11. Bert Schultz says:
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    I think the definition of ‘world” used here is incorrect. The Romans considered “the world” to comprise the civilizations that they know of, hence the phrase “The Roman World.” After the era of exploration, “the world” and Earth became synonymous. But that was just an accident of history. After the moon landing, the moon itself because a real place, part of the world. When we go to Mars, and colonize it, that will become part of the world. We are seeing this process of making the other planets of our solar system part of the world now. Notice how extra-solar planets are referred to as “alien planets,” as opposed to the planets in our solar system, which are already somehow domestic, becoming part of “the world.”

  12. John_K_Strickland says:
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    What is hard to accept for some is that sometimes we need two DIFFERENT classification systems for a single type of object. For solar system objects, (1) is the Hierarchical one: does it dominate its orbital space?. This is the primary way they decided to classify objects as planets. (2) are the physical properties, such as being spherical, size, and internal structure. Objects which do not dominate their orbital space, but qualify under the second category, can be called minor planets. The grey area comes when you have an Earth Moon type pair where one object is not massively smaller than the other, or an ice moon which is spherical, but small and undifferentiated.
    The problem that has caused such public controversy is that “PLANET” is not a technical word owned only by astronomers. The public, and especially teachers, think they are also stakeholders in what is called a planet. of course, teachers are not astronomers, who should have the final say in this matter. Pluto is no less interesting just because it is in a different category.

  13. lucasbachmann . says:
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    What I sincerely hope for is that if humanity follows the Freeman Dyson vision of outer solar system colonization – the Plutoid planets could be very important someday and should not be considered less important than the vastly different Gas Giants and Terrestrial planets. From a knowing the solar system perspective I’d like kids to know that there is an Oort cloud and asteroid belt out there just as much as the names of the mere 7 classical planets….