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NASA Scientists Propose New Definition of Planets, and Pluto Could Soon Be Back (sciencealert.com)
Rei writes: After several years of publicly complaining about the "bullshit" decision at the IAU redefining what comprises a planet, New Horizons program head Alan Stern and fellow planetary geologists have put forth a new definition which they seek to make official, basing planethood on hydrostatic equilibrium. Under this definition, in addition to Ceres, Pluto and other Kuiper Belt objects, large moons like Titan and Europa, as well as our own moon, would also become planets; "planet" would be a physical term, while "moon" would be an orbital term, and hence one can have a planetary moon, as well as planets that orbit other stars or no star at all (both prohibited under the current definition). The paper points out that planetary geologists already refer to such bodies as planets, citing examples such as a paper about Titan: "A planet-wide detached haze layer occurs between 300-350 km above the surface; the visible limb of the planet, where the vertical haze optical depth is 0.1, is about 220 km above the surface."
Things are finally going back to normal.
Nope. I am fine with Pluto going back to being a planet, but MOONS ARE NOT PLANETS. The concept of a "planet" has been around for millennia, and the moon (and later Jupiter's Galilean moons) have never been considered planets. We need to stop with the arbitrary redefinition of common words. If astronomers want a term to refer to hydrostatically stable bodies, they should make up a new word rather than trying to steal one that is already in use.
Personally I think the whole Pluto being a planet vs it being a dwarf planet makes about as much sense as arguing about whether American football deserves being called a football because players spend most of their time holding the ball and running around with it. Having said that, Pluto is a fascinating place regardless of it's label and, and since I'm not an astronomer, I am left wondering: Is the fight to make Pluto a planet again (or for that matter the original decision to demote it) based on sound scientific reasoning or is it just an ego driven pissing contest born injured national pride because Pluto is the only planet in the Sol system found by an American?
Moons are next on the hit list.
At last count Jupiter has 67 so-called moons: The four Galilean moons, plus 63 rocks.
We really need to clamp down on what counts as a moon, or every bit of space-trash will demand to be listed.
Clearly given that people like Stern have regularly given interviews decrying the decision, and going so far as to call it "bullshit" (can you say that at NASA?), it's clearly not the storm in a teacup that you want to present it as.
What the proponents did was take a term widely used by planetary geologists and have it mean something completely different - akin to dentists suddenly declaring to doctors that the heart is no longer an organ and to stop referring to it as one. And contrary to your presentation of why they did it ("to make it easier to write journal articles") without fail every last supporter I've seen interviewed about their vote has given some variant of the following reason for why they voted the way they did: "I don't want my daughter having to memorize the names of hundreds of planets." Which is so blatantly unscientific it's embarrassing that such a thing would influence their decision at all on a scientific matter.
The IAU vote was narrow, at a conference only attended at all by a fraction of its membership, on the last day when a lot of the people opposed to the definition they passed had already left because it had looked up to that point like there was either not going to be a vote at all , or one on a hydrostatic equilibrium definition - all options that they were fine with. Only 10% of the people who attended were still around.
I have a lot of issues with the last vote, and that's just the start. Here's my full list:
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 by the IAU.
2. Erroneous foundation: Current research agrees 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?
Note that the Stern-Levison parameter does not go against this, as it's built around the ability of a planet to scatter a mass distribution similar to our current asteroid belt, not large protoplanets.
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: Under the IA definition, what an object is declared as 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: (Related) An exact copy of Earth (what the vast majority of people would consider the prototype for what a planet s
I'll never forget the last thing grandma said to me before she died: "What are you doing in here with that knife?!?"
Indeed, he is flagrantly biassed. He was the head of the New Horizon's project - which just sent us a huge amount of data to study on Pluto. Studies which cost money, and having Pluto not deemed a planet anymore has, he says, made it harder to drum up funding for that research.
The answer of course is: because everything in our solar system should be studied - not just planets. One of the greatest achievements in recent astronomy has been landing a probe on a comet, because it taught us a great deal about comets (things we couldn't learn from the remnants that sometimes fall on earth). Studying mars is cool - but we SHOULD be putting probes on Eris as well.
Good probes to Titan, Europa and Ganymede are important studies to undertake in the near future - they are among the highest likelihood cases for life elsewhere in the solar system. Europan bacteria would be a fantastic discovery - Europan 'fish' an unlikely but amazing bonus - but we will never know if we don't go look.
If anything looking at planets is near the bottom of the priority list. Most of the planets are gas giants - there's only so much you can learn from something you can't land on.
Unicode killed the ASCII-art *
Any "space-trash" that demands to be listed as something else needs to be immediately identified as a "sentient being", and on behalf of all of us Earthlings the UN needs to publicly apologize to him/her/it. That is simple playground rules: you don't want to insult anybody that much bigger than you are.
As to everything else, I think the planetary geologists have it right. If it is big enough to be rounded of its own volition, it is a planet. And planets that go around another planet more quickly than they go around their star are also moons.
Corollary: that makes Earth the larger part of a binary planetary system. Which puts proper emphasis on the way the Moon creates tides that keeps the hydrosphere stirred up, which has had a major impact on how life has evolved here. Exoplanetary explorers should look for other binary planets in the Goldilocks zone as these are much more likely to have life that is similar to Earth life.
(Is a "bazinga!" called for here? Was this just another Sheldon impersonation, or did I accidentally say something insightful?)
Wow.
TL;DR but I got through enough of it to realize that most, and maybe all, the points are cogent. Above post should be stuffed down the throats of every IAU member who voted for their absurd definition of planet until they can regurgitate those points, with meaning.
Some astronomers are stupid. The phrase "educated beyond the level of their intelligence" comes to mind. This idiots should have been taught somewhere along the way that their expertise in one narrow field does not endow them with the authority to mess about in other disciplines like linguistics.