Pluto May Be "Promoted" to Boss of the Outer Realm
(Originally posted February 21, 2017 on Blogger)
I'm sure most of you have read about it already; NASA has plans to reclassify Pluto as an official planet. I've seen the headlines; "Pluto May be a Planet Again", "NASA Scientists Urge for Pluto to Regain Planet Status", "Will Pluto Have the Last Laugh?". I'm going to both explain what is really in the works in a context no one else is. A context that should have been established as far back as 2006.
The publication put out by lead author, Kirby Runyon, an impassioned, talented, and dedicated PhD student in the Department of Earth & Planetary Sciences at John Hopkins Krieger School of Arts & Sciences. He worked with NASA to help interpret data from the New Horizons spacecraft made famous for its Pluto flyby. His publication is cited at the end of this blog.
Let me preface this blog by saying that red flags go up in my brain when I see research scientists, media, or any other source argue or report a finding, discrepancy, discovery, or paradigm with emotion to the point that logical fallacies are committed. Or when they use anthropogenic descriptions for an object or function when describing it.
Science is amoral, emotionless, and tentative by nature. By amoral, and emotionless, I mean these anthropomorphic adjectives in the same way I would if I were to say that a rock or a doorknob is amoral and emotionless. They just are. To describe or defend a rock or doorknob's properties beyond facts is neither scientific, nor necessary.
Before I get to Runyon's paper, let me provide a history of Pluto as it has been reported in mainstream media, and by scientists at Universities, NASA, observatories, and elsewhere over the past decade or so. It was just over a decade ago (2006) that Pluto was reclassified as a dwarf planet by a panel of 424 astronomers at the International Astronomical Union (IAU) in Prague. I'll get to their official definition of a planet, as well as for a dwarf planet shortly. This (recent) history is steeped in emotionally-charged vernacular and partial truths. Saying such things as "Pluto was demoted..." for instance.
It seems nearly every source has been, and continues to be, guilty of this. Pluto was not "demoted". A demotion is a verb describing the lower rank or less senior position given to a person usually as a punishment either for sub-par work performance, or for vindictive reasons by an employer or manager.
Pluto was reclassified, not "demoted" and though this seems to be insignificant semantics, but when semantics has an emotional effect on people where emotion shouldn't rule the roost, then I see a problem. I'm honestly less worried about adults, and more worried about how this can affect children who may want to become scientists; a profession that requires objectivity. By saying Pluto was demoted, we are projecting emotion where it doesn't belong, and this leads us astray from science in general. Neil DeGrasse Tyson, Bill Nye, all the major news outlets, even celebrities, and school teachers at every level have described the reclassification as a demotion, and "poor little" Pluto was "kicked out" etc.
The internet exploded with images like these:
T-shirts, posters, comics, news articles, artists' depictions, gifs, websites, YouTube videos, blogs, and more have all perpetrated this conveyance of Pluto as having been wronged. I will get to how damaging this sort of anthropomorphizing is to our society in a bit, as it ties directly into the paper by Runyon et al., (2017). That may seem extreme to some; that anthropomorphizing things in science is actually damaging to society. But, as I hope to explain, it in fact is.
Runyon's paper, "A Geophysical Planet Definition", aims to reclassify Pluto as a planet. His new definition, if accepted, would make planets out of over 100 other celestial bodies in our solar system as well. Unlike aspects of the IAU definition, Runyon wants to focus his definition entirely on intrinsic physical properties of a celestial body, rather than extrinsic orbital properties.
His definition is this exactly:
"A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters."
A triaxial ellipsoid is a fancy way of saying an ellipsoid. Mathematically, it is a quadratic surface which is given in Cartesian coordinatres by x2/a2 + y2/b2 + z2/c2 = 1, where the semi-axes (x,y,z) are of lengths a, b, and c respectively. In other words, "...a round object in space that is smaller than stars", as Runyon himself suggests as an unofficial basic definition easily understood by people of all ages and academic backgrounds.
The smallest known star in the Universe is the very low mass red dwarf, 2MASS J0523-1403, that has a mass of less than 8% that of the Sun. Anything less massive than this, and nuclear fusion of ordinary hydrogen would neither initiate nor sustain and be considered sub-stellar.
Brown dwarfs are an exception to Runyon's definition. Their masses lie somewhere between that of the most massive gas giants (planets) and the low mass red dwarfs explained above. Brown dwarfs are sub-stellar celestial objects that have never undergone nuclear fusion (of ordinary hydrogen), but some are believed to be massive enough to fuse deuterium (an isotope of hydrogen). This and other reasons puts them in a category unique from planets or stars.
So, Runyon's definition of a planet includes all sub-stellar-mass round bodies in space; rounded by the effects of its own gravity, except brown dwarfs.
The IAU's definition of a planet is defined in Resolution B5 (<< this downloads as a pdf), wherein it states a planet as being:
(1) ... 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 neighborhood around its orbit.
Both Runyon and the IAU agree that one of the intrinsic properties of a planet should be its roundness, as a result of its own gravity. Where Runyon and the IAU diverge is at the extrinsic properties; orbits the Sun, clears its celestial path of other objects such as asteroids and comets. Runyon removes them completely from his definition.
Runyon makes, in my opinion, two valid points undermining the IAU's definition. He also makes a third point that I find rather weak in its argument against a certain criterion defined by the IAU as I'll explain.
First, he points out that the IAU's definition restricts planets to only those orbiting the Sun, which Runyon rightly points out as being fallacious. Since the early 1990s, scientists have discovered over 1,700 planets around other stars within our own galaxy alone, and this number is growing. Given this fact, restricting planets to only those orbiting the Sun is undeniably wrong even if it's on a technicality. The definition could replace the word "Sun" with the phrase, "its host star". But then Runyon points out the hypothetical existence of "rogue planets"; planets that have been ejected for one reason or another from their respective solar systems and now transit through interstellar space without a host star at all. So replacing "Sun" with "its host star" is insufficient.
Second, Runyon explains that the path-clearing requirement demanded of a round celestial body to qualify as a planet is mathematically distant-dependent in that the further out from the host star a body's orbit is, the more massive that body must be in order to clear its own neighborhood. He gives the example of Earth; though able to clear its orbital neighborhood in its given orbit, it would not be able to do so if its orbit were distant-equivalent to the Kuiper Belt (where Pluto's orbit passes). If by definition, Earth, or any of the rocky inner planets, qualify as planets in their given orbits, but fail to qualify at more distant orbits within their solar system, then there is a flaw in the definition. That flaw, in this case, being the neighborhood-clearing requirement.
His third point relates to his second, in that even the currently-accepted eight planets' orbits are often crossed by small bodies like "NEOs near Earth" [sic... repetitive]. That is to say, a round sub-stellar body may have cleared its neighborhood, but there will always be some small body crossing that round sub-stellar body's path; be it a comet, or asteroid, or the Starship Enterprise. It's true, objects cross planetary orbits all the time. Given this, it seems the neighborhood-clearing requirement ought to be either fine-tuned to exclude certain objects such as NEOs, or be dropped from the overall definition altogether.
Though Runyon's first two points are strong, it's my humble opinion that this latter point is weak.
The IAU's reference to clearing an orbital neighborhood was likely in reference to objects in a parallel or in at least quasi-parallel orbit to the planet in question. Comparing relatively fast-moving interplanetary (or even interstellar) objects with trajectories perpendicular to or quasi-perpendicular to a planet's otherwise-cleared orbital neighborhood is a bit like comparing apples to oranges.
These rogue objects don't need to be cleared by a sub-stellar round body whose path they cross, because these objects clear themselves by simply continuing along their trajectories.
Though, this minor point shouldn't matter as Runyon's second point does a fine job of undermining the requirement neighborhood clearing on its own.
So it seems clear, that the IAU needs to modify or completely revamp its definition. Regardless of what happens at the next IAU conference, we ought all be aware that any definition made by the IAU is not legal binding. They state it clearly on their website:
"Such decisions and recommendations are not enforceable by any national or international law; rather they establish conventions that are meant to help our understanding of astronomical objects and processes. Hence, IAU recommendations should rest on well-established scientific facts and have a broad consensus in the community concerned."
I'm not putting this here to suggest we can refer to Pluto as anything we want; that could well lead down the path of relativism which has no place in science. I put this explicit statement up so we can see that the IAU's purpose is to enhance our understanding of astronomical objects and processes. To do this, often takes years of fine tuning; as is always the case with anything in science.
Broad-stroke definitions may serve well enough for conveying general concepts, but lack the defining power necessary to truly advance a science. We can say that a star is any celestial body with mass sufficient enough to sustain thermonuclear fusion of hydrogen into helium, existing as a luminous sphere of plasma held together under the influence of its own gravity. But this says little of neutron, or hypothetical quark stars whose exotic processes require further refinement of definition. Perhaps this is a poor example, as neutron (or quark) stars are sub-categories of stars in much the same way as white dwarfs, red dwarfs, main sequence, and blue giants to name a few.
But then, "dwarf planets" are sub-categories of planets. The IAU has defined dwarf planets as any celestial object that is in orbit around the Sun (should be "its host star"), has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, has not cleared the neighborhood around its orbit, and is not a satellite (a moon).
Given Runyon's points above, we now know that if this definition of dwarf planets is likewise flawed. However, under Runyon's definition, even satellites of existing planets would themselves qualify as planets. Runyon uses the term "moon planet" a few times in his paper. Though, it seems to me that the concept of a moon-planet is a bit like reinventing the wheel.
Runyon goes on to say that the IAU uses adjectives such as "terrestrial", "[gas] giant", and "ice giant" when referring to sub-classifications of planets. He points out that the adjective small, or words synonymous to it are blatantly missing. As such, the adjectives currently used by the IAU are inconsistent. This is a bit of a stretch, but I do see inconsistency in these classifications. One refers solely to general composition without reference to size (terrestrial), while the other two combine both general composition and size ([gas] giant, and ice giant).
I'll have to take Runyon's word for it; that the eight planets recognized by the IAU are often modified by these three terms. Though, I believe scientists have perhaps a couple dozen or so terms to refer to different planets in our galaxy.
Though Runyon's definition would instantly reclassify a large number of celestial bodies such that there would be no less than 110 planets in our solar system, he assures us that kids shouldn't have to memorize them all. Just a few of interest. As he wrote, "(9?, 12?, 25?)". The number would have to be at least 17 if we're going to include Pluto, as Jupiter hosts 4 "moon planets" more massive than Pluto, Saturn's Titan, our own moon (planet), and the Kuiper Belt planet Eris... all more massive than Pluto.
Runyon gives the analogy that there are 88 constellations, and ~94 naturally-occurring elements. He points out, rightly, that most students are required to learn only a few. So then, by extension, students shouldn't have to learn all 110 planets. If our students are ever subjected to a 110-planet scenario when studying our solar system, then I agree, it seems overkill to have to know them all.
It's true, there is no need to teach every element, so long as students understand the groups, properties, and interactions between elements when calculating chemical equations. But with regard to constellations, well.. constellations aren't actually scientific by depiction. Whether a student learns one or all of them should have no bearing on her or his understanding of star formation, or their apparent migration across our night sky as Earth wobbles about its axis. For example, they should know why Polaris hasn't always been the "north star", or that nebulae are often star-forming regions in space.
I have to ask, why can't these current sub-planet bodies be studied as moons, and Kuiper Belt object(s) without reclassifying them as planets? I'm not an expert. Runyon is. Though, I can't help but get a sense that there is a level of absurdity here that ought not be reached.
I agree the IAU definitions are not satisfactory, but I don't find Runyon's broad definition satisfactory either. He makes some revealing statements in his paper, which ties back into my earlier points about anthropomorphizing things in science. And regardless of what planets end up being defined as, this brings me to my main point of this blog... that scientists (and the media), are failing at conveying science to the public. The public is perhaps just as important to the world of science as scientists themselves, because their collective opinion influences policy; policy that often directly funds, and/or dictates what scientists can and cannot do in their respective laboratories; whether those labs are in a building, underground, out in nature, or in space.
What is most revealing of everything Runyon et al., wrote in their paper, is that they are concerned with public perception. In the paper's case, this perception is with regard to Pluto specifically. But I can just as easily translate that ill-desired perception to any number of things within the many realms of science (stem cell research, CRISPR, nuclear fusion, interplanetary travel, etc).
He writes, "...in our experience, [the public] assume[s] that alleged "non-planets" cease to be interesting enough to warrant scientific exploration...". He goes on to write, "...a common question we receive is, "Why did you send New Horizons to Pluto if it's not a planet anymore?"" Continuing, "To mitigate this unfortunate perception, we propose a new definition..."
Therein lies the impetus to his desire to redefine what planets are. Not because it refines our scientific categorization of celestial objects within our solar system, but because it reclassifies over 100 bodies such that they will be interesting enough to garner public interest. Though he doesn't say this directly, it seems implicit that this translates to policy support. Hey, if it works then great. I'm all for it. If I feel it doesn't undermine science and underestimates our youth (students of all ages).
And to this, I believe his definition not only undermines the science, but underestimates our youth, and ignores the bigger problem: scientists' and celebrity "scientists" near ad nauseum use of anthropomorphically-charged explanations when conveying their or others' science to the public.
'Pluto has been demoted.' 'Poor little Pluto has been kicked out of the planetary club' 'Aww, Pluto has a heart clearly visible on its surface, and we've broken it!' 'Size doesn't matter'. Uffff. Size may not matter, but mass does.
The depictions and explanations of Pluto's reclassification suffer from a kind of Pathetic fallacy that has absolutely no place in science. Rather than reclassifying celestial objects such that an obnoxious number of them become planets in order to make kids and adults interested in them, perhaps we as scientists (not that I'm a true scientist) should stop babying them and treating them as if they are incapable of learning beyond a sappy level, and teach them with adjectives that are more representative and meaningful.
Rather than tell the public that Pluto was demoted, and to get over it, how about we explain what actually happened in 2006; that a panel of over 400 scientists have refined the definition of a planet. As such, Pluto is now reclassified as a "dwarf planet". If that term is too anthropomorphic in nature, then how about we call upon the power of Shakespeare and make up a term, like Gravity Sphere, or something unique. People wouldn't think, en masse, that Pluto's reclassification equates to making it unimportant. The fact they do says something about the way they're receiving this information. I honestly don't expect better from the media, but I do from scientists and those who speak on their behalf.
To me, Runyon's paper makes two things clear. That the IAU needs to revamp their definition of what a planet is, and more importantly, scientists and celebrity "scientists" need to stop talking to the public like they're kindergartners, and stop talking to children as if they're incapable of learning at more advanced levels. If we keep up this trend, we'll see people inventing thermodynamically-impossible things like the WaterSeer, pouring millions into transit systems that bring all the dangers of space down to seismically-active Earth, geologists believing we can terraform a planet lacking an internal dynamo, decent gravity, and a magnetic field, and of course see some less-than-stellar policies making it through Congress, while some good ones never see the light of day.
“By the pricking of my thumbs, Something wicked this way comes.”
― Shakespeare, Macbeth
As always, thanks for reading.
A GEOPHYSICAL PLANET DEFINITION
Lunar and Planetary Science XLVIII (2017)
K.D. Runyon1, S.A. Stern2, T.R. Lauer3, W. Grundy4, M.E. Summers5, K.N. Singer2, 1Johns Hopkins University, Dept. of Earth and Planetary Sciences, Baltimore, MD, USA (firstname.lastname@example.org), 2Southwest Research Institute, Boulder, CO, USA, 3National Optical Astronomy Observatory, Tucson, AZ, USA, 4Lowell Observatory, Flagstaff, AZ, USA 5George Mason University, Dept. of Physics and Astronomy, Fairfax, VA, USA.
*There is no Star Trek episode titled, "Portmanteau Problems"