Fine. Stronger than magnitude 6 (or whatever Vespa and Uranus are), and less than magitude whatever the moon is. Basically I am giving planet back its old meaning - the only one that makes sense - “wandering star”.
I dunno; galaxy and star have more coherent definitions than planet. It’s too all-inclusive. We want it to mean something, we just don’t know what, or how to define it.
What’s your definition of approximately? Whatever you come up with, it’s going to be arbitrary. There is no good way to delineate between a planet and an asteroid that fully and completely encompasses the terms.
But now you’re just being completely arbitrary. The proposed IAU rules might be mostly arbitrary, but they’re at least trying to put things into categories where things will have some interesting similarities. If you want planets to be just Mercury, Venus, Mars, Jupiter, and Saturn just make that the rule instead of some post hoc made up rules to get you those and only those, just to try to make it look like it’s some objective category. Any rule which puts Earth and Venus into different categories is no longer a scientific classification at all, and you can’t possibly expect a scientific body to endorse it.
And any rule that puts Venus and Jupiter in the same category is no more scientific.
You might be right on my take on the subject, tho. I am arguing that ‘planet’ has no good scientific definition, so I shouldn’t try to give it one. Kinda makes sense as it should be a historical definition, not a scientific one.
I gotta disagree with this one, tho:
That’s the whole problem. The new defintion for planet is so broad that the interesting similarities are overshadowed by the even more interesting contrasts. What makes Mercury more similar to Uranus, and less similar to a large, spherical comet?
Well, okay, that’s fair enough. We’ve pretty clearly got 3 categories here that are pretty dissimilar being lumped together as planets. Still, they do have a unifying theme, i.e., big round stuff going around a star. I don’t see how that’s any more problematic than main sequence, red giants, white dwarfs, and neutron stars all being classified as stars.
I’m not sure about Neutron Stars, but don’t the first three give off energy by a high amount of nuclear fusion going on?
Actually, I think what’s even more confusing than that is trying to differentiate between Brown Dwarves and Jovians. When does a plant like Jupiter stop being a planet and start being a rather dark star? Doesn’t Saturn give off more energy than it can absorb from Sol?
and I still say planet is a useless scientific term. so there 
Sure, but in the case of a white dwarf it’s He fusing into C, not H into He. Point is, “big thing shooting out energy from nuclear fusion” isn’t any more unified a category than “round thing orbiting a star” is - and as you note, the lower bound of the star category isn’t at all distinct from the upper bound of the planet category. Conclusion: categories in astronomy are almost all arbitrary.
As much as I hate to nitpick something that’s so obviously beside the point, but the “white dwarf” phase of a star’s life cycle takes place at the end. No fusion takes place in white dwarfs.
More on topic, I think what needs to be considered here is this: what is the purpose of a term like planet? The fact that all this fuss is essentially coming from the problem of how to classify four or five extremely small and insignificant makes me think it doesn’t matter one way or another whether “planet” has a strict definition. Everyone, or at least anyone who cares, knows what a planet is. I’d say this means the term is serving its purpose.
Astronomy is not math. There are a lot of really vague definitions in astronomy. The term “main sequence star,” which is pretty well-defined compared to “planet”, could describe any number of stars that from a human’s perspective are radically different. Yet there also exists an incredibly rich and deep vocabulary to give more information where necessary, all rigorously defined in terms of morphology, or physics, or observational data. If you need to be specific, and I always encourage being as specific as possible, use the rigorous terms. Say that Sedna is a kuiper belt object, or whatever, if that’s what gets your point across. If you don’t need to, don’t want to, or think your audience wouldn’t understand, go with “planet.”
That’s an excellent question. As you rightly point out, Astronomers don’t really need it, as they have plenty of good vocabulary and maths at their disposal to express what they need to rigorously.
Perhaps this is supposed to be more for the benefit of the interested public, and for the benefit of students of astronomy at the earliest levels who probably rely on hierarchies of meaning to learn the concepts?
Oh yeah, this geek on TV, from some outfit called NAUSEA or something like that, not only said that my anus was a planet, but he also said it was a “gas giant”. Now I’ll be the first to admit our trailer gets a bit fragrant when the missus makes cabbage and beans with yogurt sauce, but that ain’t no reason to go talkin’ ‘bout my farts on TV. Fuck, if a man can’t lay one or two to take the pressure off once in a while, what’s the use of livin’?
Anyway, I got a better idea as long as the gummint is deciding which planets to place where and all.
See, I can never remember how to spell or pronounce those things around my ass that hurt and itch all the time.
I have to get Tyler, my kid, to read me what it says on the side of the Prep H tube before I can remember what they’re called. And how did the “a” and the “e” in haemorrhoids (or however the Hell you spell it) get stuck together like that? I thought maybe it was the ointment got on the box.
Anyhow as long as the astronomy folks is so powerful interested in my asshole to talk about it on TV, and as long as we’re into finding new names for stuff, how about this idea?
Let the astronomy geeks have the word “hemrrrrohodids” to use in astronomy. Chances are those Poindexters can figure out how to spell the word better than me. Now what we would do, see, is apply the name “heamohrroyeds” to that bunch of sickly looking rocks orbiting between Mars and Jupiter. We make up a story that they’re named after Hemos, the Greek God of broken rocks or olives or something. Those nerds would love it.
Now you see, that frees up the word “Assteroids” to use where it really can do the most good. To describe the things you get on your ass! What could be more perfect? I would never have any trouble remembering or pronouncing it or spelling it.
So stop worrying about Pluto and Xena (cartoon dogs and TV dykes — is that all you people have to worry about?) and let’s start the campaign to change the meaning of “assteroids”. Write to the gummint today! If we all pull together we can fix the hemmorrrrohoids problem once and for all!
Don’t worry, Bryan. I got it, at least.
Geologists don’t argue about what a continent is: they accept that it is largely a cultural construct. After all, there’s no good reason to call Europe and Asia separate continents and there’s no bright line that separates the Australian continent from the island of Greenland.
I didn’t invent this argument by the way:
http://www.nytimes.com/aponline/us/AP-Planet-Hunter.html?_r=1&oref=slogin
So there’s nothing wrong with keeping Pluto. One astronomer proposes that all bodies orbiting a star that are Pluto-sized or larger should be designated as “Planets”. Bodies that orbit a planet would be called, “Satellites” or “Moons”, so Charon would be out.
Arbitrary you say? Sure, but so what?
Such a policy would keep the number of Sol planets down to a manageable size, but still allow the possibility of discovering new ones.
I was listening to a story about this whole thing on the BBC World Service last night, and they were exclusively referring to 2003 UB313 (or whatever it’s actually called) as “Xena”.
I’m all in favour of this. Sure, Xena comes from a TV series (and not a particularly good one), but weren’t the Roman and Greek myths just an ancient form of mass entertainment anyway?
Tune in next time, when Zeus assumes the form of a Swan to seduce a mortal woman, Pandora opens her box, Aphrodite and Dionysus host a party, and Hercules finally gets the chance to pursue his singing career at the Pink Parthenon Nightclub… All in the next thrilling instalment of ‘‘Olympiad!’’
If we’re going for names for planets, I suggest:
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Planet Aaaaargh
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Planet Ni
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Planet Ecky-Ecky-Ecky F’Tang
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Planet Bender
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Planet of the Apes
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Planet Gilligan
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Planet Klink
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Planet Rimmer
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Planet Kryten
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Planet Lister
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Planet Tardis
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America
I’ve heard “Buffy” bandied about as a name for one of the KBOs as well…
I took an astronomy/geology course on the planets five years ago. The professor (Dr. Stefan Dieters–he said he was part of a team that dicovered Pluto’s atmosphere) told us that there is a recent trend among some astronomers to call Uranus and Neptune “Ice Giants” rather than “Gas Giants” because of their temperature and composition. So that would add one more category.
As far as I’m concerned, Pluto is a planet. Ceres, I’m still skeptical.
I think the standard for Pluton/trans-Neptunians is that they be named for an underworld god. Quaoar is named for a Native American deity I’m rooting for Cthulhu, personally, although it would be horribly unfair if the last word went to anyone other than the discoverer.
There is however already the precedent that the discoverer does not always get the chance to name the planet, ever heard of planet George?:
Yes, the delineation between ‘planet’ (as it is culturally known), and ‘asteroid’ (as it is culturally known), is arbritary.
The IAU have proposed essentially a mass cutoff; if its massive enough for:
then its a planet. The issue of ‘planet’ (i.e. those that would be culturally considered a planet) or ‘dwarf planet’ (the largest asteroids) is that anything smaller than Mercury is a dwarf planet.
Of course there is the issue of how to determine if something is in hydrostatic equilibrium; the simplest of which is “does it have a circular cross section?” which is a direct consquence of the mathematical definition: “does the net force on the body equal zero?”. If so, then its in hydrostatic equilibrium.
This is something that we can calculate/work out, so it is workable in practice. Scientifically, its probably as good as you’re going to get if you want a catch all term for something that orbits a star that’s not another star, but is in hydrostatic equlibrium. Further, its one that can be applied to extra-solar systems too, else we’re left without a term to describe an extra-solar planet until we determine what its composition is.
I know this isn’t perfect, not by a long shot, but scientifically, its a start. Culturally, on the other hand, it does cause confusion.
Can’t. There is already an asteroid with that name.
And Xena won’t stick - it is the tongue-in-cheek nickname given to it by Dr. Brown because it is the fabled “Planet X”. Even he doesn’t want Xena to be the permanent name.
Sua
It now appears they are leaning toward demoting Pluto, as it is not “the dominant body in its orbital zone”. They’re “also stepping back from trying to define all planets in the universe, and sticking to our solar system”.
I find this last development quite disappointing. The whole reason to favor the “hydrostatic equilibrium” criterion was its universality, and “sticking to our solar system”, in my mind, just delays an inevitable problem, which will be how to define planets in other solar systems that can (as we already know) look radically different from our own. Whatever the final criteria wind up being, I think it’s better to bite that bullet now for the benefit of future investigators and students. Oh well.