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NASA's New Horizons Shows Pluto's Moon Charon Is a Strange, New World
MarkWhittington writes: NASA's New Horizons has returned a stunning series of images of Pluto, the dwarf planet that resides on the edge of the solar system, revealing a strange new world of ice mountains and glaciers of frozen nitrogen. NASA also released images of Pluto's largest moon Charon. Scientists expected a plain ball of rock pockmarked with craters, but what they saw was anything but plain and monotonous.
First, the IAU definition:
1. Nomenclature: An "adjective-noun" should always be a subset of "noun". A "dwarf planet" should be no less seen as a type of planet than a "dwarf star" is seen as a type of star.
2. Erroneous foundation: Current research suggests that most planets did not clear their own neighborhoods, and even that their neighborhoods may not always have been where they are. Jupiter, and Saturn to a lesser extent, have cleared most neighborhoods. Mars has 1/300th the Stern-Levison parameter as Neptune, and Neptune has multiple bodies a couple percent of Mars's mass (possibly even larger, we've only detected an estimated 1% of large KBOs) in its "neighborhood". Mars's neighborhood would in no way would be clear if Jupiter did not exist - even Earth's might not be. Should we demote the terrestrial planets as well?
3. Comparative inconsistency: Earth is far more like Ceres and Pluto than it is like Jupiter, yet these very dissimilar groups - gas giants and terrestrial planets - are lumped together as "planets" while dwarfs are excluded.
4. Poor choice of dividing line: While defining objects inherently requires drawing lines between groups, the chosen line has been poorly selected. Achieving a rough hydrostatic equilibrium is a very meaningful dividing line - it means differentiation, mineralization processes, alteration of primordial materials, and so forth. It's also often associated with internal heat and, increasingly as we're realizing, a common association with subsurface fluids. In short, a body in a category of "not having achieved hydrostatic equilibrium" describes a body which one would study to learn about the origins of our solar system, while a body in a category of "having achieved hydrostatic equilibrium" describes a body one would study, for example, to learn more about tectonics, geochemistry, (potentially) biology, etc. By contrast, a dividing line of "clearing its neighborhood" - which doesn't even meet standard #2 - says little about the body itself.
5. Mutability: What an object is declared at can be altered without any of the properties of the object changing simply by its "neighborhood" changing in any of countless ways.
6. Situational inconsistency: An exact copy of Earth (what the vast majority of people would consider the prototype for what a planet should be), identical down to all of the life on its surface, would not be considered a planet if orbiting in the habitable zone of a significantly larger star (harder to clear zone), or a young star (insufficient time to clear), a star without a Jupiter equivalent (no assistance in clearing), or so forth.
Crowd: What do we want? Fry: Fry's dog! Crowd: When do we want it? Fry: Fry's dog!
New rule: there's only 8 rivers on Earth, and all others are "dwarf rivers" and don't really count as rivers. In order to retain the use of the word "river" in a context that is relatively closely related to its historical usage when people were primitive tribesmen and only knew of a few rivers in their area, a line has to be drawn somewhere. It is far more logical to draw that line above the Brahmaputra than below it. If you are advocating for every river which is large enough to be too deep and fast flowing to ford a river -- you're going to have upwards of 100000 of them, and that's just what we know of right now.
New rule: there are only organs in the human body, and all others are "dwarf organs" and don't really count as organs. In order to retain the use of the word "organ" in a context that is relatively closely related to its historical usage, a line has to be drawn somewhere. It is far more logical to draw that line above the spleen than below it. If you are advocating for every object which is large enough to have a distinct biological function, and is not a part of another organ an organ -- you're going to have many hundreds if not thousands of them, and that's just what we know of right now.
New rule: there are only 8 elements, and all others are "secondary elements" and don't really count as elements. In order to retain the use of the word "element" in a context that is relatively closely related to its historical usage, a line has to be drawn somewhere. It is far more logical to draw that line above bismuth than below it. If you are advocating for every particle which contains a unique number of protons to be called an element -- you're going to have 118 of them, and that's just what we know of right now.
Shall I keep going?
It is in no way, shape or form scientific to define what something is based on whether schoolchildren can memorize a list of all of them. Time and time again, ancient peoples have created names for things thinking that there's only a small number of them, and later scientists discovered that there's actually a vast diversity of them. Well, guess what, you deal with that and accept that the universe is a fascinating place rather than trying to hide it with definitions that aren't even internally consistent or in alignment with our models of what actually cleared most "neighborhoods" in our solar system (hint: it wasn't planets like Mars).
And you certainly don't do so in opposition to the very perception of the word itself. People look at pictures of Pluto and they see a planet. Because it's a giant chunk of rock orbiting a star - yes, there are bigger ones, but it's still huge, so large that gravity crammed it into a sphere, setting of processes of mineralization, tectonics, and so forth - which more to the point appear to be still active to this day. People turn on Star Trek and when they see the Enterprise arrive at a body like Pluto, they expect to hear Captain Kirk say "Beam me down to the planet", not "Beam me down to this... hmm, Spock, I'm not sure what to call it, could you run a long-range scan to see if it has "cleared its neighborhood"... oh wait, I forgot, "planets" can only be objects in orbit around the sun, there is no name for whatever this thing is!"
Crowd: What do we want? Fry: Fry's dog! Crowd: When do we want it? Fry: Fry's dog!
The planet Pluto is a planet because planet is a word, and words are part of language and language is an UNCONTROLLED interchanged between people.
So you're really getting upset by this, but in doing so you're accepting the IAU as an authority on the matter. You could simply continue to call Pluto a planet and it is a planet and nothing has changed about planet Pluto.
See point 19.
Really its not about 'disagreeing' with IAU, its simply that they don't control the language and if their decision doesn't have any traction in the language then tough. Its not worth fretting about it, just keep calling it a planet and its a planet.
Yes, it's stupid, confusing, and the IAU needs to revisit their bad decision even if only for this reason, rather than letting it fester.
You apparently see no problem grouping together the rocky inner planets with the enormous gas and ice giant outer planets. Yet you have a fundamental problem with grouping the rocky inner planets with bodies like Ceres and Pluto that they share far more in common with.
And yes, Pluto and Charon are KBOs. KBOs are an orbital designation, one type among many. Mercury, Venus, Earth and Mars also have an orbital designation, for example - "inner planets". An orbital designation can quite happily sit side by side with a classification of an object based on what its actual physical characteristics are.
You're avoiding the question: why? What's so damned logical about grouping Mars with Jupiter, but not with Ceres or Pluto? And what was "currently deemed planets" included Pluto until the IAU decided to butt in, so that argument buys you nothing. They changed the status quo, they weren't preserving it.
Hydrostatic equilibrium is a highly logical dividing line. It has meaning, unlike whether a neighborhood has been cleared (usually by a larger second party, I should add, not by the planet itself - the IAU definition is built on a foundation that is a lie, that the "8 planets" cleared their own neighborhoods). When a body relaxes into hydrostatic equilibrium, it not only changes shape, but it differentiates and remineralizes. It becomes a fundamentally new type of body, with internal structure, non-primordial minerals, and internal heat flows (even if they - like everything else - eventually die). One studies bodies that are in non-hydrostatic equilibrium to learn about the primordial solar system, while one studies bodies that are in hydrostatic equilibrium to learn about planetary evolution, to search for life, etc. It's a distinct dividing line. Let's not pretend that it's not there. Or that it doesn't need a term to refer to it. Such as the term we've been using this whole damned time - "planet".
Which is why the ancients knew of Uranus and Neptune, right? Oh wait... Sorry, I guess they're not planets!
And again: why don't we just lock all sciences down by what the ancients knew? Sorry, guys, there's only 8 elements - copper, sulfur, tin, gold, antimony, mercury, and lead - everything else is just "earths"! Or maybe we should just stick with the 4 elements? Because that's the whole point of science, after all - rote memorization of things that people in long-extinct societies declared in their ignorance.
"all" is of course a falsehood. For many KBOs, Neptune has little effect. And here's a category for you to ponder while you're at it: the Sednoids. One of the leading theories is that there's a body out there, potentially in the ballpark of the size of the Earth, that's scattering them;
Crowd: What do we want? Fry: Fry's dog! Crowd: When do we want it? Fry: Fry's dog!
WTF? How do you even know all this stuff? Seriously... I hold my doctorate in Applied Mathematics and, honestly, I can barely wrap my head around half of what you said and I'm not even sure the total is half. I'm assuming you're a hobbyist and not some sort of astrophysicist. If you are an astrophysicist, then still, how the hell do you manage to retain that well enough to just nonchalantly type it out on Slashdot?
Don't get me wrong - I'm impressed and you're the reason I come here and have been coming for many years. However, sometimes you freaks amaze me. How do you cram that much into your head without vomiting it up?
"So long and thanks for all the fish."