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posted by martyb on Monday April 03 2017, @06:54PM   Printer-friendly
from the we-need-cleanup-in-orbit-3 dept.

Arthur T Knackerbracket has found the following story:

It turns out that Earth is not a planet. Asteroid 2016 H03, first spotted on April 27, 2016, by the Pan-STARRS 1 asteroid survey telescope on Haleakala, Hawaii, is a companion of Earth, too distant to be considered a true satellite.

"Since 2016 HO3 loops around our planet, but never ventures very far away as we both go around the sun, we refer to it as a quasi-satellite of Earth," said Paul Chodas, manager of NASA's Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California.

Asteroid 2016 H03 is proof that Earth has not cleared the neighborhood around its orbit. Therefore, under the definition of a planet vigorously defended by the IAU [International Astronomical Union] since the adoption of Resolution 5A on August 24, 2006, Earth is a 'dwarf planet' because it has not cleared its orbit, which is the only criteria of their definition that Pluto fails. (I think we'll eventually discover that very few of the 'planets' have cleared their orbits).

Most of us who were baffled by the IAUs declaration and outraged at the obvious discrimination of Pluto knew there was something wrong, even if we couldn't put our finger on it — we just 'knew' Pluto was a planet, right?

[...] Here's what all of us non-scientists intuitively understood all along: "A planet is defined as an astronomical body that "has not undergone nuclear fusion, and having sufficient self-gravitation to assume a spheroidal shape" — in other words, it's round and not on fire.

How could the distinguished scientists be so wrong?

-- submitted from IRC


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  • (Score: 3, Interesting) by melikamp on Monday April 03 2017, @07:00PM (21 children)

    by melikamp (1886) on Monday April 03 2017, @07:00PM (#488294) Journal

    Is there going to be a link to a white paper, written by a scientist, even if a citizen scientist, which argues for this interpretation? Here are some of the "neighborhood clearing" criteria in use, which one of them is violated, and by how much?

    https://en.wikipedia.org/wiki/Clearing_the_neighbourhood#Criteria [wikipedia.org]

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  • (Score: 2) by massa on Monday April 03 2017, @07:22PM (13 children)

    by massa (5547) on Monday April 03 2017, @07:22PM (#488306)

    There is the one criteria that Pluto will never satisfy: having a planet-like orbit (in the ecliptic plane, not crossing other bodies' orbits, etc)

    • (Score: 0) by Anonymous Coward on Monday April 03 2017, @07:51PM

      by Anonymous Coward on Monday April 03 2017, @07:51PM (#488330)

      Not a criteria to be a planet. Not even in the various proposed criteria at the infamous IAU meeting that caused the kerfuffle.

      At the end of the day "planet" will be defined by common usage, not by any sub-group of scientists.

    • (Score: 4, Insightful) by number6x on Monday April 03 2017, @09:00PM (10 children)

      by number6x (903) on Monday April 03 2017, @09:00PM (#488369)

      This is not what is meant by 'cleared the neighborhood around its orbit'. If it was, planets would not be allowed to have moons.

      Asteroid 2016 H03 is completely dominated by Earth's gravity. If the Earth wasn't there Asteroid 2016 H03 would be circling the sun at its own pace. In essence, Asteroid 2016 H03 orbits Earth's orbit, and its path is controlled and determined by the effects that Earth's gravity has on it. This makes it similar to asteroids in Earth's trojan points.

      A better (but completely silly) argument would be that Earth, and all the other planets, have not 'cleared' their orbits because, occasionally, a comet comes in and crosses their orbits, thus 'proving' that their orbit is not cleared. It would be a very pedantic interpretation of the definition.

      Just quit getting so hung up about the definition of a planet, because it is kind of arbitrary and will change depending on the group of researchers needs. Labeling and classifying things belongs to the type of science often referred to as 'butterfly collecting'. The task of labeling things and sticking them in the correct pigeon holes.

      Butterfly collecting is sometimes useful. Listing chemicals by their properties led to the periodic chart. The property categories were later explained when the make up of atoms as a positively charged nucleus surrounded by 'shells' of electrons. atoms that had full shells acted in a certain way. atoms that were a few electrons short acted in their way, and atoms that had a few electrons in their next shell acted in their way. Each of these groups formed columns in the periodic table. The explanation of why the atoms exhibited their groups of behavior came long after the behavior was recorded in the periodic table.

      Butterfly collecting the various groups of animals leading to Kingdom, Phyla, Class, Order, Family, Genus, and Species led to understanding of evolution and the observation how traits were passed down across generations. Some of these labels had to be re-adjusted after genetic testing was developed. Not every animal that looked alike was as closely related as thought, and some closely related animals looked different from each other. However, the 'butterfly collecting' approach was a really good first approximation.

      Defining the groups of objects in the solar system is done to help us gain new insight into commonalities and differences. It is like applying a filter. You can apply this filter now, and another filter later, re-aligning the definitions.

      That is what this is about, made up labels and definitions. I don't mean to imply that they are just random and arbitrary. They are meaningful and helpful. They are not just arbitrary. However, another set of meaningful and helpful definitions and labels may be useful for other purposes and lead to different insights.

      • (Score: 3, Informative) by hendrikboom on Tuesday April 04 2017, @12:50AM

        by hendrikboom (1125) Subscriber Badge on Tuesday April 04 2017, @12:50AM (#488459) Homepage Journal

        Labeling and classifying things belongs to the type of science often referred to as 'butterfly collecting'.

        Labeling and classifying things belongs to the type of science often referred to as 'taxonomy'.

      • (Score: 2) by bzipitidoo on Tuesday April 04 2017, @04:30AM (7 children)

        by bzipitidoo (4388) on Tuesday April 04 2017, @04:30AM (#488526) Journal

        Oh come on, the article was flamebait. You're right, this asteroid does not demote Earth's status from planet to dwarf planet.

        The article points up a problem. A comet crossing a planetary orbit does not change the status of a planet. Yet, planetary status does depend on external factors. Should it? I would say it should depend on external factors as little as possible. Move Pluto further out so that not only does it not cross Neptune's orbit, it is not in any resonance at all with Neptune, and what happens? Suddenly Pluto qualifies as a planet because its neighborhood is clear? That's the basic problem with the definition.

        Move Earth into orbit around Jupiter, and suddenly Earth is no longer a planet, it is only a moon. Planets orbit stars or nothing. An object that orbits a planet is a moon. And that's okay. It's a useful distinction.

        What about a round body too small to fuse elements in interstellar space, orbiting the galactic center rather than any star? Is that a planet? Sure it is! If Mercury gets ejected from the solar system it would not suddenly lose its status as a planet.

        • (Score: 0) by Anonymous Coward on Tuesday April 04 2017, @05:30AM

          by Anonymous Coward on Tuesday April 04 2017, @05:30AM (#488547)
        • (Score: 2) by dry on Tuesday April 04 2017, @05:39AM (5 children)

          by dry (223) on Tuesday April 04 2017, @05:39AM (#488551) Journal

          Isn't one of the definitions of a planet that it orbits the Sun? Currently there are exactly 8 planets in the universe and if Mercury was ejected, it would no longer be a planet.

          • (Score: 2) by bzipitidoo on Tuesday April 04 2017, @06:21AM (3 children)

            by bzipitidoo (4388) on Tuesday April 04 2017, @06:21AM (#488559) Journal

            If you want to be extremely pedantic, there are only 5 planets: Mercury, Venus, Mars, Jupiter, and Saturn. The ancients could not see Uranus or Neptune, and did not realize that what they were on, the Earth, belonged in the same category as the 5 wanderers.

            I do not see any useful distinction between planet and exo-planet. They all orbit suns, or are rogue planets. We've found thousands of exo-planets.

            Can a planet orbit a black hole, and still be considered a planet? Why not?

            • (Score: 2) by maxwell demon on Tuesday April 04 2017, @07:12AM (2 children)

              by maxwell demon (1608) on Tuesday April 04 2017, @07:12AM (#488567) Journal

              They all orbit suns, or are rogue planets.

              No. They orbit stars. There are many stars, but only one of them is called sun, just like there are many planets, but only one is called earth.

              It's bad enough that the term "moon", which used to be a name just for the earth moon, now has double use as both a specific body and a class of bodies. No need to add more ambiguities like that, when we already have a word for the class. What's wrong with "star"?

              --
              The Tao of math: The numbers you can count are not the real numbers.
              • (Score: 2) by bzipitidoo on Tuesday April 04 2017, @12:59PM (1 child)

                by bzipitidoo (4388) on Tuesday April 04 2017, @12:59PM (#488614) Journal

                "sun" means the star or stars within the same solar system as the planet referred to. Sol is our sun.

                Here is a pic of SUNset on Tatooine: https://en.wikipedia.org/wiki/Tatooine#/media/File:SW_binary_sunset.png [wikipedia.org]

                "moon" is not a problem. Can call ours Luna, if "the Moon" (with capital 'M') doesn't suit.

                • (Score: 2) by dry on Wednesday April 05 2017, @03:56AM

                  by dry (223) on Wednesday April 05 2017, @03:56AM (#488996) Journal

                  Too lazy to load your link, but I didn't realize that Tatooine was close enough that the Sun was noticeable.
                  Just like we can talk about Sirius rise or setting (very important to the ancient Egyptians), Aliens around Sirius could talk about the Sun setting as the Sun would be one of the brighter stars in the sky.
                  I talk English, not Latin, and call the Sun the Sun and the Moon the Moon.

          • (Score: 2) by Scruffy Beard 2 on Tuesday April 04 2017, @06:25AM

            by Scruffy Beard 2 (6030) on Tuesday April 04 2017, @06:25AM (#488561)

            Nice catch. It looks like exoplanets are merely undefined by the IAU though:

            The IAU therefore resolves that planets and other bodies, except satellites,
            in our Solar System be defined into three distinct categories in the
            following way:
            (1) A planet is a celestial body that
            (a) is in orbit around the Sun,
            (b) has sufficient mass for its self-gravity to overcome rigid body forces
            so that it assumes a hydrostatic equilibrium (nearly round) shape, and
            (c) has cleared the neighbourhood around its orbit.

            Definition of a Planet in the Solar System [iau.org]

            I also now know why the press-release incorrectly classifies Earth as a planet: it was an error in the footnote of the resolution!

            The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

      • (Score: 1) by All Your Lawn Are Belong To Us on Tuesday April 04 2017, @05:06PM

        by All Your Lawn Are Belong To Us (6553) on Tuesday April 04 2017, @05:06PM (#488701) Journal

        Well said! My personal view is that we who are amateur astronomers (and professional astronomers) should have other fish to fry and things to be concerned with than reopen the, "Pluto is a planet," argument again. But I'm comfy *either* way.

        At least I do. Someone else's mileage may vary.

        --
        This sig for rent.
    • (Score: 4, Insightful) by butthurt on Monday April 03 2017, @10:11PM

      by butthurt (6141) on Monday April 03 2017, @10:11PM (#488410) Journal

      > not crossing other bodies' orbits

      It's true that Pluto crosses Neptune's orbit, but it isn't true that Neptune crosses Pluto's?

  • (Score: 5, Insightful) by Immerman on Monday April 03 2017, @07:33PM (2 children)

    by Immerman (3985) on Monday April 03 2017, @07:33PM (#488317)

    Heck, forget Earth - Jupiter hasn't cleared it's orbit either, though I suppose the Lagrange Points get special consideration.

    • (Score: 4, Insightful) by julian on Monday April 03 2017, @09:24PM

      by julian (6003) Subscriber Badge on Monday April 03 2017, @09:24PM (#488386)

      Can we just abandon this futile attempt at platonic essentialism? Almost everything in the Universe is describable by its place on an n-fold continuum. There is no perfect form of "planetness" that real objects conform to more or less. Pluto is a rock/ice body with a certain mass, it has certain neighbors that share it's orbit or orbit around it. It has any number of characteristics that might be interesting to study. There are an infinite number of ways to prioritize these and weight them for assessing its membership in some category humans invented.

      "Planet" is a label humans use because it is useful for the daily work of astronomy and planetary science. It's a good definition if it's useful. It's a bad definition if it causes more confusion than it dispels. Pluto will continue moving about its orbit just fine no matter what you call it.

      So is Pluto a planet? It depends what you're interested in studying. A geologist might say yes. An astronomer might say no. We just have to be clear which definition we are using and why.

    • (Score: 0) by Anonymous Coward on Tuesday April 04 2017, @12:00AM

      by Anonymous Coward on Tuesday April 04 2017, @12:00AM (#488444)

      Lagrange points get the same "special consideration" as orbital resonances, such as the 1:1 resonance of "quasi-satellites" like 2016 HO3 with Earth, and 2:3 resonance like Pluto and the other plutinos have with Neptune.

      Nobody serious denies that there's a useful distinction to be made between bodies such as Jupiter, which control a large region of space, and smaller bodies like asteroids and plutinos whose orbits are controlled by a nearby body in the first group, and the various criteria proposed to discriminate these classes of bodies are more in agreement than not, and all take such things into account. The disagreement is whether this classification, regarding a body's dynamical effects in relation to the rest of the solar system should be part of the definition of a planet, or whether planethood should be determined solely by properties of the body itself, and the dynamical classification should be another layer on top. (IAU tried to split the difference with "planet" and "dwarf planet", which is just a horrible naming convention.)

  • (Score: 2) by frojack on Monday April 03 2017, @07:38PM

    by frojack (1554) on Monday April 03 2017, @07:38PM (#488321) Journal

    even if a citizen scientist

    So now we discriminate against good old home grown motherland scientists and insist on H1-B scientists!??!

    --
    No, you are mistaken. I've always had this sig.
  • (Score: 2) by AthanasiusKircher on Monday April 03 2017, @07:42PM (2 children)

    by AthanasiusKircher (5291) on Monday April 03 2017, @07:42PM (#488325) Journal

    Apparently the author doesn't know. As he himself says in TFA:

    I’m not qualified to define what ‘clearing the orbital neighborhood’ means, nor define the importance of the location of the barycenter of two bodies one orbiting the other. I only understand what most school children do, that a planet is round, and not on fire. I’ve attached an illustration.

    I really don't get why people are so upset about this. Even if the criteria are not precise (though this guy admits he doesn't know enough about "clearing orbit" criteria to have a clue whether they are precise or not). it seems excluding Pluto is about the only way to get to a reasonably consistent definition that doesn't balloon the "solar system" to a huge number of planets. Right now, there are something like a hundred potential dwarf planets [wikipedia.org] that could satisfy the definition of "round and not on fire," and the estimate is that there are probably 200 in the Kuiper belt, and a LOT more beyond.

    So what's his solution? He says his post is "satire" in the sense that he doesn't REALLY believe Earth is not a planet, but he doesn't propose an alternate definition that doesn't lead us to revise the definition of the "planets" in the Solar System every other week. If Pluto is so worthy of the designation, what about the other Kuiper belt objects? Or is he going to draw an arbitrary distance line from the sun? Or some other arbitrary distinction?

    Also, I can't even believe I'm still giving attention to this guy, but why does he care so much about 2016 HO3? Yes, it follows an interesting orbital trajectory with Earth, but there are a bunch of near earth asteroids [wikipedia.org] -- probably a few thousand bigger than 2016 HO3 -- why isn't he talking about them??

    Even one of the most prominent foes of the redefinition was instrumental in formulating the one of the metrics for orbital clearing [wikipedia.org] that shows a huge gap between the major planets and things like Pluto and Ceres. Instead of demoting Pluto though, his argument just wants to call the 8 major planets "überplanets," which is still creating an equivalent distinction, just prefixing a term on a different group. What difference does it make whether we have hundreds of "planets" and 8 "überplanets" vs. hundreds of "dwarf planets" and 8 "planets"? Given the much, much longer history of using the word "planet" alone for the major planets, it probably makes a little more sense to go with the "dwarf planet" idea... otherwise it's kind of like Starbucks calling a small drink a "tall."

    Lastly, is it even worth pointing out that Pluto is STILL a "planet" (a term that still basically follows his definition of "round and not on fire"), just a "dwarf" one?

    • (Score: 0) by Anonymous Coward on Tuesday April 04 2017, @03:22AM (1 child)

      by Anonymous Coward on Tuesday April 04 2017, @03:22AM (#488514)

      So what's his solution? He says his post is "satire" in the sense that he doesn't REALLY believe Earth is not a planet, but he doesn't propose an alternate definition that doesn't lead us to revise the definition of the "planets" in the Solar System every other week.

      Um, yeah, he does. "Round and not on fire." As far as I can tell, you think he'll want it revised every week because you've assumed he wants to somehow exclude everything except the "Classic Nine", but he never says that.

      If Pluto is so worthy of the designation, what about the other Kuiper belt objects?

      Are they round and not on fire? Planets! (So not tiny irregular-shaped ones, nor any cold-fusioning ones that may exist.)

      Or is he going to draw an arbitrary distance line from the sun?

      Why? Surely things don't stop being rounded by their own gravity, or spontaneously combust, because of some arbitrary distance line?

      Or some other arbitrary distinction?

      Again, why? This guy gets enough things wrong*, there's no need to criticize him for wanting arbitrary distinctions when you're the only one proposing them.

      (IMO, the fact that many satellites become planets under such a definition is far more likely to bother people and result in arbitrary distinctions than "b-b-but... hundreds of planets!". Personally, I don't mind that either -- I'm quite capable of handling the idea that something can be a planet and a moon at the same time.)

      Even one of the most prominent foes of the redefinition was instrumental in formulating the one of the metrics for orbital clearing that shows a huge gap between the major planets and things like Pluto and Ceres. Instead of demoting Pluto though, his argument just wants to call the 8 major planets "überplanets," which is still creating an equivalent distinction, just prefixing a term on a different group. What difference does it make whether we have hundreds of "planets" and 8 "überplanets" vs. hundreds of "dwarf planets" and 8 "planets"?

      Well, the difference is that Stern's scheme has 3 labels; both "überplanets" and "unterplanets" are subsets of "planets". These labels make grammatical sense.

      Lastly, is it even worth pointing out that Pluto is STILL a "planet" (a term that still basically follows his definition of "round and not on fire"), just a "dwarf" one?

      Well, that's exactly the problem; under the IAU's definitions, a dwarf planet is not a planet at all. In an attempt to split the middle, they picked the worst nomenclature possible.

      You can either have the set "planet" with two subsets "dwarf planet" and "??? planet" (where ??? can be any adjective, such as "classical" or "über-"), or you can have two sets "planet" and "???" (where ??? is anything not of the form "$ADJECTIVE planet"; "planetoid was suggested (but has unfortunate history as a synonym for "asteroid"), and I think "planetino" was tossed around?); I don't have strong feelings either way. But having mutually-exclusive sets labeled "planet" and "dwarf planet" is just a horrible thing to do.

      *My favorite was "since a planet is a planet regardless of what system it’s in (unless the IAU would like to vote against that?)"; of course the very IAU resolution that demoted Pluto specifically defined a planet to be "in orbit around the Sun". Or right in TFS, we have "(I think we'll eventually discover that very few of the 'planets' have cleared their orbits)"; as you say, the numerous Earth-crossing asteroids, but also the trojans and plutinos, have already proved that few if any planets have "cleared their orbits" -- for a sufficiently ridiculous definition of that phrase. It's a pretty valid criticism of the IAU definition that it doesn't specify a definition for "cleared the neighborhood around its orbit", but substituting ridiculous definitions and saying "See, it makes no sense!" is silly, and imagining that 2016 HO3 is somehow the first body you can combine with your ridiculous definition to "discredit" the IAU is both silly and astronomically illiterate. Frankly, I'm not too happy to be defending this clown...

      • (Score: 2) by maxwell demon on Tuesday April 04 2017, @07:21AM

        by maxwell demon (1608) on Tuesday April 04 2017, @07:21AM (#488568) Journal

        Um, yeah, he does. "Round and not on fire."

        He might still want to add something else. Or he'll have to label a soccer ball a planet because it is round and not on fire (of course as soon as someone sets it on fire, the soccer ball loses its planetary status. I'm not sure whether it then is a sta, though ;-))

        --
        The Tao of math: The numbers you can count are not the real numbers.