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posted by martyb on Thursday August 02 2018, @06:10PM   Printer-friendly
from the Number-Nine,-Number-Nine,-Number-Nine... dept.

Planet Nine: 'Insensitive' Term Riles Scientists

The International Astronomical Union (IAU) famously reclassified Pluto as a "dwarf planet" in 2006. That decision remains highly controversial today, as made clear by the new note, which appeared in the July 29 issue of the Planetary Exploration Newsletter.

The note:

ON THE INSENSITIVE USE OF THE TERM "PLANET 9" FOR OBJECTS BEYOND PLUTO

We the undersigned wish to remind our colleagues that the IAU planet definition adopted in 2006 has been controversial and is far from universally accepted. Given this, and given the incredible accomplishment of the discovery of Pluto, the harbinger of the solar system's third zone — the Kuiper Belt — by planetary astronomer Clyde W. Tombaugh in 1930, we the undersigned believe the use of the term 'Planet 9' for objects beyond Pluto is insensitive to Professor Tombaugh's legacy.

We further believe the use of this term should be discontinued in favor of culturally and taxonomically neutral terms for such planets, such as Planet X, Planet Next, or Giant Planet Five.

35 researchers signed the note, including Alan Stern, principal investigator of the New Horizons mission.

Of more interest may be this proposal concerning future exploration of Uranus and Neptune:

Outer Solar System Exploration: A Compelling and Unified Dual Mission Decadal Strategy for Exploring Uranus, Neptune, Triton, Dwarf Planets, and Small KBOs and Centaurs

Related: Uranus and Neptune Are Potential Targets for 2030s Missions
Another Trans-Neptunian Object With a High Orbital Inclination Points to Planet Nine
CU Boulder Researchers Say Collective Gravity, Not Planet Nine, Explains Orbits of Detached Objects
Planet Nine Search Turns Up 10 More Moons of Jupiter


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  • (Score: 5, Interesting) by AthanasiusKircher on Thursday August 02 2018, @07:02PM (8 children)

    by AthanasiusKircher (5291) on Thursday August 02 2018, @07:02PM (#716396) Journal

    so we get the ridiculous notion that at 5 AU, it's a planet, at 55 AU it's a 'dwarf planet'?

    You do realize that there are actual mathematical metrics for measuring this stuff, right? Not just a bunch of Pluto-haters looking at charts of the solar system and saying, "Hmm, yep, that one's clear!"

    You can see the popular ones summarized here [wikipedia.org]. And you can see in the table near the bottom that all metrics (including ones developed by people who were against the redefinition of Pluto) show a major gap of several orders of magnitude between Ceres/Pluto and the other planets. (And note all of these take into account distance from the sun into their definition, so the standards ARE different for planets farther from the sun.)

    To be clear, I don't really care what we call Pluto. All definitions are to some extent arbitrary. But pretending that this "clearing the neighborhood" issue isn't actually a feature of astronomical interest and pretending that there's not a very significant gap in any reasonable metric to quantify that -- well, that's at best disingenuous and at worst a display of plain ignorance.

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  • (Score: 2) by AthanasiusKircher on Thursday August 02 2018, @07:25PM (1 child)

    by AthanasiusKircher (5291) on Thursday August 02 2018, @07:25PM (#716405) Journal

    Also, to show that I'm really agnostic on this, here's an interview with a real planetary scientist [space.com] (one of the guys who actually proposed the first metric for clearing the neighborhood) about why he thinks the IAU definition is bad.

    Point being: the IAU definition of a "planet" may or may not be a good one by various criteria, but "clearing the neighborhood" is a real thing and a potentially interesting attribute of a body.

    • (Score: 4, Informative) by requerdanos on Friday August 03 2018, @02:33PM

      by requerdanos (5997) Subscriber Badge on Friday August 03 2018, @02:33PM (#716716) Journal

      You do realize that there are actual mathematical metrics for measuring this stuff, right?

      I'm really agnostic on this

      That isn't obvious, to be honest.

      Whether you are agnostic, or a God named after a planet, the fact is that the argument under discussion is that if the rules indicate that a big semi-spherical gas giant "yes" is a planet at 5 astronomical units, but the identical big semi-spherical gas giant "no" is not a planet at 55 astronomical units while orbiting the same star, and the rules do indicate this, then that's an interesting feature of those rules.

      But wait, what if you really carefully and scientifically look for things existing planetary bodies have in common, like (mostly) clearing their orbits? Does that change the fact that Juipter counts "yes" as a planet at 5AU but "no" would not count at 55AU?

      No, it doesn't change that fact, so going on about how careful, cool, or earth-shatteringly awesome orbit-clearing is, doesn't show you to be "Agnostic"--it just shows that you're missing a valid point that would be interesting for discussion.

      point being "clearing the neighborhood" is a real thing and a potentially interesting attribute of a body.

      With all due respect, while that's a point, it's not the point under discussion in this thread. No one is saying that orbit-clearing is not a real thing, nor that it's uninteresting; just observing that it would only apply to planets within a certain radius from the Sun.

      That is relevant here (unlike orbit-clearing monomania, which isn't) because we are talking about the possible existence of a big semi-spherical thing in orbit around the sun that is really really far out compared to the other ones (which we call planets, dwarf planets, etc.). We're calling the posited far-out body "[Ice [Giant]] Planet (3|5|9|X|etc.)". In talking about such a body, the point comes up that even if it's identical to one of the other bodies that firmly count as "planets", it may very well itself not count because at a more distant location it might not have things in common, like--you guessed it, or failed to--orbit-clearing of its much larger-diameter orbit.

      I get that you appear unhappy about that, and that orbit-clearing seems important to you. Those things don't make this apparent contradiction within the rules uninteresting nor irrelevant--in this context, it's especially interesting and relevant.

  • (Score: 2) by bob_super on Thursday August 02 2018, @08:46PM (5 children)

    by bob_super (1357) on Thursday August 02 2018, @08:46PM (#716447)

    None of this would have happened if anything that feels like a planet was just called planet, and the special 4+4 were just called Major Planets. Emphasize positively, rather than negatively, especially because grants.
    Any marketing guy could have told them that.

    • (Score: 2) by AthanasiusKircher on Thursday August 02 2018, @09:40PM

      by AthanasiusKircher (5291) on Thursday August 02 2018, @09:40PM (#716465) Journal

      Agreed. The original "clearing the neighborhood" paper called them uberplanets, I believe. Everything sounds more awesome in German.

    • (Score: 2) by jelizondo on Thursday August 02 2018, @11:10PM (3 children)

      by jelizondo (653) Subscriber Badge on Thursday August 02 2018, @11:10PM (#716481) Journal

      Actually the problem started when other planets we discovered, at that time I wrote an article about the "12 planets" because the count had increased to such and jokingly felt pity for the poor kids who would have to learn three more names.

      A good note is on Wikipedia [wikipedia.org]

      • (Score: 3, Disagree) by bob_super on Thursday August 02 2018, @11:40PM (2 children)

        by bob_super (1357) on Thursday August 02 2018, @11:40PM (#716491)

        My point was that it doesn't matter if the solar system has 253 planets (256 would matter, because of the 8-bit overflow).
        Teach the kids the 8 to 10 Major Planets, and a selection of of the most interesting other bodies (Pluto, the big moons, notable comets).
        "There are too many to remember everything" is a pretty shitty reason to demote a whole class of objects, especially when considering that wiki thingy. Promote the special ones instead.

        • (Score: 1) by jelizondo on Friday August 03 2018, @01:14AM (1 child)

          by jelizondo (653) Subscriber Badge on Friday August 03 2018, @01:14AM (#716518) Journal

          You are quite correct, I was not disagreeing, simply pointing to the fact that once more "planets" had been found some people felt the need to redefine what "planet" is, particularly because Pluto has a very large moon (Charon) that makes it almost a binary planet. Anyway, I never saw the need to redefine the status, in mind, it serves no purpose.

          • (Score: 3, Interesting) by bob_super on Friday August 03 2018, @01:24AM

            by bob_super (1357) on Friday August 03 2018, @01:24AM (#716519)

            > Pluto has a very large moon (Charon) that makes it almost a binary planet.

            I'd go as far as calling it a binary outright, because the center of mass of that system is outside of Pluto's body.
            Since there's at least two more moons orbiting that binary system, i'm not quite sure what the secondary threshold would be to call it a quaternary system ... maybe the center of mass of the ensemble always staying in the cone formed by the big two (and by extension to ternary or more, the region of space between the main bodies) would be a good idea.

            The Solar system has :
              - 4 Major rocky planets (inner ones - few moons)
              - 4 Major Gas/frozen giant planets (outer ones - lots of moons)
              - At least one binary system
              - A lot of other planets, many still to be discovered.
              - other stuff that's not in hydrostatic equilibrium, or is on highly eccentric orbits
            How is that nomenclature a topic of arguments ?