[meteorite-list] Astronomers to Decide What Makes a Planet

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Wed Aug 3 14:43:29 2005
Message-ID: <42F1102A.29804D91_at_bhil.com>

Hi, Ron,

    You'll notice that I put quotes around the word "rules."

    Yes, there is no formal definition for a planet. There never has been, only a
working understanding of what was meant.

    There were differences; it has been a topic of discussion. But, there are
"working rules," by which I mean that one knows what others in the field think and
why.

    The consensus compromise was on Pluto. Yes, it was a planet, but it was too
small (debatable) and we don't like it. Among other things, because it didn't fit
with the other "planets" in the scheme of things, compositionally unique.

    Well, there are enough big KBO's to establish a new class in the scheme of
things now, obviously. The refuge for those who didn't like Pluto was that KBO's
are all small, iceballs, giant comets, etc., hence not essentially "planet-like."

    The compromise rested on the truth of the "small" notion. 2003UB313 blows the
compromise out of the water. By the given reasoning of those who deny the
"planethood" of KBO's, 2003UB313 qualifies as a planet. What if 2003UB313 turns out
to be bigger than Mercury? How do you disqualify it?

    Darren thinks KBO's have too many volatiles to be a "planet." What do you do
with Saturn; toss it out too? Ok, Saturn's out, along with the rest of the Jovians.
MexicoDoug thinks Jupiter is "too big" to be a "planet;" it's a failed brown dwarf.
Ok, Jupiter's out. Whoops, already was!

    By my count, we now have four planets left. No, Mercury's too small. I forget
it was out. Make that three. Well, Venus is too hot and Mars is too cold. Gee, I
guess there's only ONE planet after all: Earth, the Center of the Universe, Home
Sweet Home.

    Haven't we been here before, about 500 years ago?

    Truth: there is a population of hundreds or thousands of bodies, some planet
sized, in a zone or region of the solar system. They are consistently composed of a
comparably even mixture of felsic (and possibly mafic) minerals and abundant
cyrogenic minerals. They possess a complex inner dynamic, are known to be capable
of vulcanism and likely to additionally possess a wide variety of known and unknown
geologic processes.

    Sounds like planets to me, not just one planet but PLANETS, in the decidedly
plural. The Universe is not getting smaller. Really, it isn't.

    "It is not a game, it is just a classification." Truth is the ultimate game.
People fight over it. "Classification" is just what you call a thing, and in
science you call it what it IS, so it matters more than anything else. The name
determines what you think of it as, how you conceive it. The word stands for the
nature of the thing's reality.

    The unending arguments that consume quantum theory, for example, are because
every conceptual identification, or "name," is about the reality of REALITY. It
matters, believe me. The arguments ARE quantum theory. This case of "planets" is
not as pure an example, but it is important.

    The reference to classificatory disputes in meteorites is misleading because
for a century meteorites taught us more about the universe than you could otherwise
observe, but currently and for the past few decades, we have learned more about
meteorites from our exploration of space than we could have learned from the rocks
themselves. Even so, meteorites are invaluable as a "sample return" mission, of an
informal sort.

    The trailing, rather than leading, role of meteorite studies is that for all
those years, no one looked over LAFAYETTE or NAKAHLA and said, "O My God, this
sucker's from Mars!" I bet somebody thought it, but was far too cautious to say it.
If somebody did, it didn't draw much attention.

    You have to have a certain amount of guts. Gene Shoemaker is a good example:
guts, and he was right. Luis Alvarez is another. Opponents used to grumble that he
already had a Nobel Prize; he could say anything he wanted. Louis Frank has, and
John O'Keefe had, the same guts; are/were they right? Most folk have a totally
negative answer to that, but the jury of time may partially modify their opinion,
or not, as the truth may be.

    Brown is engaging in a necessary piece of politics, of advocacy, that's all. So
am I in my tiny tiny way, but our hearts are pure :-} You try to influence
decision-makers BEFORE they make decisions. True for politicians; true for IAU.

    The ONLY reason for disqualifying KBO's from EVER being planets is the mistaken
notion that they are "only comets" and can't never be planets no matter how big
because of their compositional nature. This is completely irrational. How can you
exclude them because they are roughly 50% volatiles when you admit the Jovians,
some of which may be ENTIRELY volatiles?

    Mr. Spock, help me here on this "logic thing."

    Next week's IAU decision is only a momentary thing, always subject to revision.
Good old science. In researching KBO's, I found several websites that defined the
"outer edge" of the Kuiper Belt at 52 AU, asserting that no more KBO's would be
found beyond that distance.

    Wonder what they thought when 2003UB313 turned up at 97 AU? Yeah, it comes in
to 52 AU. Hold on to that... Maybe they're all eccentric and perihelion in the
50's. So what? Big is big, and a population is a population.

    What happens when Brown or somebody finds a really big KBO? Like bigger than
Mars at 147 AU and magnitude 20.7? Twenty years ago, no KBO's. Ten years ago,
scores of KBO's. Today, hundreds of KBO's. You see a trend there? What if there's a
Uranus sized one at 360 AU and magnitude 22?

    Remember, the anomalies that led to the discovery of Neptune and Pluto are not
fully accounted for. They certainly are not accounted for by Pluto itself,
unmassive as it is. There are still unaccounted residuals, too small to be useful.
Then, there's the Pioneer anomaly...

    Time will tell. It always does, if you keep looking.


Sterling Webb
------------------------------------------------
Ron Baalke wrote:

> >
> > Two, 2003UB313 IS a planet under the "rules" that were in effect at
> > the time of discovery.
>
> There is no formal definition for a planet, and that it the crux of the
> problem. The IAU will be providing a formal definition soon.
>
> >You don't change the rules after the game is over
> > because you don't like the outcome, not even in Paris (or do you?).
>
> It is not a game, it is just a classification, which is being modified
> to accomodate the latest data. Just look at how meteorites are classified.
> We would like to classify each meteorite cleanly into its own subgroup.
> But we occasionaly run into a meteorite that doesn't fit very well
> in the current classification scheme, so we temporarily label
> it as 'anomolous'. We eventually modify the classification to
> accomodate these anomolous meteorites, usually by creating a new subgroup, or
> expanding the definition of an existing subgroup. Same thing with the planets.
> We have a few anomolous objects that don't fit very in the current
> classification, which was poorly defined to begin with. We are going
> through a process of reclassifcation based on the latest data, which
> was long overdue.
>
> Ron Baalke
>
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Received on Wed 03 Aug 2005 02:42:50 PM PDT