[meteorite-list] Planet V (for Five)

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Fri Apr 28 12:07:53 2006
Message-ID: <009101c66a8e$63048a20$e420e146_at_ATARIENGINE>

Hi, All,

    Well, sure, if as the author states, "we believe
that such a big object never existed in the outer solar
system," then you have to find something else.
    That's because he belongs to the High Mass
Density Nebula School and not the Low Mass Density
Nebula School. If you have high mass, the planets
accrete in a big hurry from small planetesimals and
it's all over quick. If you have low mass, accretion
takes longer and it needs lots of big planetesimals.
    If you have high mass, though, the nebular gas
is there while the planets are accreting, and the drag
of trying to shove a blanking Jupiter (and all the planets)
through a thick cloud makes so much drag that they
spiral rapidly into the Sun and vanish. So, something
(who knows what?) has to blow off the entire mass
of the nebula in the nick of time and save the planets
and push them back out again.
    The biggest difficulty is that this kind of accretion
would produce planets that are all very much alike,
since they accrete from small planetesimals that are
all remarkably similiar because a high mass nebula is
well mixed. It would produce planets far more alike
than the planets we've actually got, which look more
and more different the more we learn about them.
    You can see that High Mass theories have problems. It
was not a popular theory at all until... TaDa! We discover
all these 100+ extrasolar planets and, OMG! There are
Jupiters and Super-Jupiters orbiting closer to their Suns
than Mercury... Suddenly, the High Mass Density Nebula
Theories are the chic new thing and everybody wants one!
    Of course, this kind of solar system generates the
biggest best signal for detection by the method being used
and a solar system like ours wouldn't register at all. And sure
enough, if you plot the discoveries versus their distances
you can see that these are highly biased samples. There
are more discoveries at greater distances instead of less,
which means a great volume of stars is likely to contain
some even more extreme systems than a small volume.
    They represent less than 4% of the selected likely
targets. I think they're the oddballs, and the other 96+%
all have solar systems that are "normal," whatever that is.
At least they don't have 10-Jupiter mass planets orbiting
only 20-30 million kilometers off the star!
    Anyway, you got any idea just how close Jupiter would
have to be to Uranus to roll it over? Like eighteen-wheelers
playing Chicken on dirt road, raised to 100th power... Like
all the rest of the High Mass Density Nebula theory, it
requires some very close calls and lots of lucky coincidences.
    As Bohr said to Pauli, "We all agree that your theory is
crazy. Now we're arguing about whether or not it's crazy
enough to be true!"
    No big objects in the outer Solar System!?


Sterling K. Webb
----------------------------------------------------------------
----- Original Message -----
From: "Darren Garrison" <cynapse_at_charter.net>
To: <sterling_k_webb_at_sbcglobal.net>
Cc: <meteorite-list_at_meteoritecentral.com>
Sent: Thursday, April 27, 2006 9:29 PM
Subject: Re: [meteorite-list] Planet V (for Five)


On Thu, 27 Apr 2006 19:49:55 -0500, you wrote:

> Even Jupiter has a three-degree tilt. Ya know
>its gonna take a good whack upside the planet to
>tilt Jupiter! Uranus is tilted over on its side; it
>takes an impact with an Earth mass object to
>deliver that amount of change in momentum.

Or maybe not:

http://www.msnbc.msn.com/id/12498416/

Early gravitational pull tilted the big planets
New theory departs from earlier idea that tilts were caused by impacts

Updated: 3:59 p.m. ET April 26, 2006
WASHINGTON - An early gravitational dance made the giant planets tilt the
way
they do - which is different from the way Earth and the other smaller
planets
tilt, an astronomer reported on Wednesday.

The shift probably happened billions of years ago when the bigger planets in
our
solar system were closer together than they are now, and the gravity of each
one
exerted a pull on the others, said Adrian Brunini of the Facultad de
Ciencias
Astronomicas y Geofisicas in Buenos Aires.

This "neutral gravitational interaction" caused Jupiter, Saturn, Uranus and
Neptune to have tilted axes that were determined as they moved through the
solar
system to take their current positions far from the sun, Brunini said in a
telephone interview.

This is a departure from an earlier theory that holds that the massive
planets'
tilts - or obliquities, as astronomers call them - were caused by collisions
with Earth-sized space rocks during the early period of the solar system.

"This model has some problems that were not clear how to solve," Brunini
said.
"For example, we believe that such a big object never existed in the outer
solar
system."

In research published in the current edition of the journal Nature, Brunini
used
numerical models to show that the outer planets' obliquities could have been
created by gravitational interactions.

All the planets in our solar system have tilted axes but the bigger ones
have
axes that lean at a constant angle, while the smaller ones like Earth have
obliquities that can change.

Despite the potential for change, Earth's axis has been leaning about 23
degrees
for millions of years and is almost completely stabilized by the moon's
gravitational pull, Brunini said, but Mars' axis might change over tens of
millions of years.

For humans, the reliability of Earth's tilted axis is important since it is
responsible for the change of seasons. At the point in its annual orbit
where
Earth's northern hemisphere leans away from the sun, it's winter; when the
southern hemisphere tilts away, it's winter there.

While the more massive planets have stable obliquities, they range in size
from
a nearly perpendicular 3 degrees for Jupiter to about 97 degrees for Uranus.
Brunini said.
Received on Fri 28 Apr 2006 02:38:39 AM PDT