Hi, E.P., List,
> Yes, cometesimals - about 75 meters or so, which
> themselves can then accrete chaotically over time,
Yes, but nobody thinks cometesimals contain
enough iron-nickel to form a differentiated body.
They may, but nobody believes it...
When I expressed a doubt about accreting big
bodies out in the Kuiper Belt to a professional, he
said, "What else could it be?" Good question.
> ...over time...
The problem is elbow room and simple geometry.
How much elbow room do you have? Accretion
occurs because things bump into each other, because
the space is crowded, like a NY cocktail party.
Clearly, the Earth accreted. If it sucked up every
rock from 0.80 AU out to 1.30 AU, it was drawing
on a "zone" with an area of about 0.80 "square AU's."
(The area of a circle 1.3 AU in diameter minus the
area of a circle 0.8 AU in diameter = "the Accretion
Zone.") Yes, it was a volume, because it had thickness,
but it was a flat disc.
It was crowded. Rocks kept meeting rocks. It
happened in a hurry -- blam, Blam, BLAM, all done.
10 million years? 30? 50? Opinions vary, but quick,
all agree.
Out in the Kuiper Belt, very narrowly defined as
from 38 AU out to 48 AU, there's 1583 "square AU's"!
That's almost 2000 times more room! Your odds of
bumping into something are 2000 times smaller.
Imagine you're in a ballroom with 3999 other
people, all 4000 of you milling around in constant
motion and blindfolded so you can't look where
you're going: bump, Bump, BUMP.
Now, imagine that you're in the SAME ballroom
with one other person (just the two of you). What
are the chances of you two (blindfolded and with
ear plugs) colliding?
Well, since your odds of meeting up are 2000
times smaller, it's going to take 2000 times as long
for it to happen. Hey, no problemo! If the Earth
accretes in a snappy 10 million years, then objects
in the Kuiper Belt will accrete in only... scribble,
scribble... 20 Billion Years!
No, wait! Does that sound wrong to you?
You see the problem...
Well, the theoretical dynamicists must have
an answer, something we haven't thought of,
right? They do indeed have solutions. What
are they?
Simple, just put 100 times more mass in the
Kuiper Belt (or 200 times more or 500 times more)
and it speeds things up to where bodies can accrete
there in ONLY a billion years or less! Or more...
Wow, the Kuiper Belt must be MASSIVE!
Oh, no, they reply, the whole thing has less than
0.10 Earth masses for all objects big and small.
All that mass is gone...
I smell a problem. It took the inner solar system,
where things accrete in a flash, 600 million years to
clean up the leftovers (the Late Bombardment, you
remember; it was a big hit). The same process in the
Kuiper Belt? With 100 times the mass, it will take
20 times as long (6 billion years). The leftovers
should still be there. If not, where'd the mass go?
There are lots of "mass-wasting" theories. I didn't
invent that silly term; that's what they're called.
Not to go on too long, the answer is: it got swept
under the rug. There are numerous complicated and
unlikely scenarios. Julio Fernandez and school push
a theory in which Neptune, pumped up by a resonance
with Saturn, spirals outward (while the other giants
spiral inward), with Neptune pushing the KB in front
of it, compressing it and making fast accretion happen,
until Neptune finally stops with the KB on its doorstep,
where Neptune can then spend billions of years
perturbing the rest of the mass away, and leaving
little total mass for the Kuiper Belt.
Of course, they could just be WRONG about the
mass-poor Kuiper Belt. Look a sharp, economical test
of Kuiper Belt theory described in:
http://www.nature.com/nature/journal/v442/n7103/full/442640a.html
The data had already been collected by NASA.
(The full article is at:
http://www.nature.com/nature/journal/v442/n7103/full/nature04941.html)
They found perhaps 1000 times more mass than
theory allows. So maybe the mass is still there?
One prediction of theory is that the Kuiper Belt has
a sharply cut-off outer edge, and that past that edge,
there are no more TNO's all the way out to the Oort
Cloud, a great deserted and empty zone, with a sign
at 42 AU or 48 AU that says: "Now leaving the Solar
System. No Gas Stations for 20,000 AU." In other
words, there's nothing out there TO find.
This, of course, is where all the bolts come loose
and the wheels fall off! This is exactly where we are
finding things. First called the "Scattered Disc" (on
the assumption that Neptune tossed'em out there) and
then the "Extended Scattered Disk," or the "Distant
Detached Disc," we now have a slew of large interesting
objects that Neptune could never have had anything to
do with.
Finding Sedna was kind of a last straw. Brown, who
discovered it says, "Sedna shouldn't be there. There's
no way to put Sedna where it is. It never comes close
enough to be affected by the sun, but it never goes far
enough away from the sun to be affected by other stars...
Sedna is stuck, frozen in place; there's no way to move it,
basically there's no way to put it there - unless it formed
there. But it's in a very elliptical orbit like that. It simply
can't be there. There's no possible way - except it is.
So how, then?"
Sedna has been "explained" as an Oort Cloud object,
which tacitly moves the inner Oort Cloud boundary in
from 20,000 AU to under 1000 AU and creates an "Oort
Disc" in the bargain! Those Oortians are sneaky... They
creep right up on you.
Then some theoreticians have claimed that Sedna
is the captured planet of another star. Kenyon at Harvard
CfA: "If we find planets with orbital inclinations of more
than 40°, it is almost certain that these are extrasolar
planets formed in another solar system." Then, along
comes ERIS, the former 2003 UB313, which meets that
qualification. Extra-solar planet?
> ...it would be real nice to get some
> good spectra of 2003 EL61 right now...
Oh, for one lousy gritty gram of sample return, as
there are only about 80 isotope assays any one of which
could decide between material formed with Our Star or
formed with Some Other Star!
All these high inclination objects have also provided
a big boost to the "Sun's Companion Star" theories
we all remember so well, like Nemesis. It still has its
backers, and they're all elated. Of course, what they
don't tell you is that you don't need a brown dwarf
star to perturb disc objects in inclination; all you
need is an Earth mass object at 1200 AU. The Outer
Outer System is waiting to be discovered... I think.
Then, there's 2005 XR190, code name "Buffy." If
Sedna is impossible, then "Buffy" is impossibility cubed!
The size of Ceres, it's in a nice normal almost CIRCULAR
orbit inclined at 45 degrees to the solar system at 52 to
62 AU's out, dynamically independent of any influence
from ANY solar system objects and is equally impossible
as a star capture. "Buffy" is "The Theory Slayer"! Poof!
Your life's work is dust...
That we are finding ANY high-inclination objects is
a miracle. Astronomers are STILL just looking at the
Ecliptic and nowhere else. A high-inclination object is
near or in the Ecliptic plane for just 2% of its orbital
travel, so for every one you find there, there are 49
others you're MISSING, by not looking where they
are!
Duh!
One of the best times ever is when Reality just flat
outruns Theory and leaves it panting in the dust, don't
you think? I certainly do.
Of course, another effect of this situation is that
the Theory Machines all get their throttles cranked up
to "Hyper Overdrive" and a lot of Theory Juice gets
splattered all over the place. What we actually need
is to let the Theory Machines cool down and collect
more Reality
Sterling K. Webb
----------------------------------------------------------
----- Original Message -----
From: "E.P. Grondine" <[EMAIL PROTECTED]>
To: <meteorite-list@meteoritecentral.com>
Sent: Tuesday, September 19, 2006 9:23 AM
Subject: Re: [meteorite-list] 2003 EL61, IN PERSON
> Hi Sterling, list -
>
> "but core-forming planetesimals all the way out in
> Kuiper Belt?!"
>
> Yes, cometissimals - about 75 meters or so, which
> themselves can then accrete chaotically over time,
> with the heavy elements always gravitationally
> precipitating towards the center - the lighter
> volatiles always on the outside - and you have
> delivery to the surfaces of larger bodies -
>
> Given the problems this presents us for dealing with
> cometary impactors, it would be real nice to get some
> good spectra of 2003 EL61 right now, but as always,
> this kind of study recieves a low priority from the
> failed nuclear physicists who control the telescopes
> and observing budgets -
>
> by the way, the 64 fragments of SW3 should be in the
> Earth's vicinity in 2022, though I don't have any dead
> on forecasts yet - as a matter of fact, I wonder where
> they are, and how this is being handled, so if anyone
> hears anything, please pass it on -
>
> good hunting,
> Ed
>
>
>
