[meteorite-list] Study: Earthlike planets may be common

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Mon Sep 11 00:01:09 2006
Message-ID: <004901c6d556$e714c680$5f5ae146_at_ATARIENGINE>

Hi,

    The same scientist who just published this study,
which says that close Jupiters allow terrestrial planets
with lots of water, also published in May, 2006 a study
that rules out a different set of solar systems with Jupiters:
http://arxiv.org/abs/astro-ph/0605136

    This study eliminates terrestrial water-rich worlds only
when the Jupiters orbit between 1.6 AU and 3.5 AU. So
that eliminates such systems (which is most of the extra-
solar planetary systems we've already discovered) as good
candidates for Earth-like water-rich worlds. The two studies
together indicate you can have water-rich Earth-like worlds
with close-in Jupiters or with far-off Jupiters, but not with
"in-between" Jupiters.

    I quote from the abstract:
    "We present results of 460 N-body simulations of
terrestrial accretion from a disk of Moon- to Mars-sized
planetary embryos. We systematically vary the orbital
semimajor axis of a Jupiter-mass giant planet between
1.6 and 6 AU, and eccentricity between 0 and 0.4.
We find that for Sun-like stars, giant planets inside
roughly 2.5 AU inhibit the growth of 0.3 Earth-mass
planets in the habitable zone. If planets accrete water
from volatile-rich embryos past 2-2.5 AU, then
water-rich habitable planets can only form in systems
with giant planets beyond 3.5 AU. Giant planets with
significant orbital eccentricities inhibit both accretion
and water delivery. The majority of the current sample
of extra-solar giant planets appears unlikely to form
habitable planets."

    In other words, you can only have Earth-like planets
if there are no Jupiters hanging around the neighborhood.
Good as it is to pin these things down, do we really need
a big computer study to tell us that if Jupiter orbited
the Sun at, say, the distance of Ceres, our planet Earth
simply wouldn't be here? Didn't we know that already?


Sterling K. Webb
-----------------------------------------------------------------
If this is a repeat post, I apologize. The first one
seems to have never showed up as far as I can tell.
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----- Original Message -----
From: "Darren Garrison" <cynapse_at_charter.net>
To: <meteorite-list_at_meteoritecentral.com>
Sent: Friday, September 08, 2006 10:54 AM
Subject: [meteorite-list] Study: Earthlike planets may be common


http://www.cnn.com/2006/TECH/space/09/08/earthlike.planets.reut/index.html
Received on Mon 11 Sep 2006 12:01:03 AM PDT