SETI public: The stability of the terrestrial planets with a more massive "Earth"

• Previous message: LARRY KLAES: "SETI public: Planetesimal Formation without Thresholds I and II"

Paper: astro-ph/0508670
Date: Wed, 31 Aug 2005 08:54:30 GMT (630kb)

Title: The stability of the terrestrial planets with a more massive "Earth"

Authors: \'Aron S\"uli, Rudolf Dvorak and Florian Freistetter

Comments: 11 pages, 12 figures, submitted to MNRAS
\\
Although the long-term numerical integrations of planetary orbits indicate
that our planetary system is dynamically stable at least +/- Gyr, the
dynamics
of our Solar System includes both chaotic and stable motions: the large
planets
exhibit remarkable stability on gigayear timescales, while the subsystem of
the
terrestrial planets is weekly chaotic with a maximum Lyapunov exponent
reaching
the value of 1/5 Myr. In this paper the dynamics of the
Sun--Venus--Earth--Mars-Jupiter--Saturn model is studied, where the mass of
Earth was magnified via a mass factor $\kappa_E$. The resulting systems
dominated by a massive Earth may serve also as models for exoplanetary
systems
that are similar to our one. This work is a continuation of our previous
study,
where the same model was used and the masses of the inner planets were
uniformly magnified. That model was found to be substantially stable against
the mass growth. Our simulations were undertaken for more then 100 different
values of K for a time of 20, in some cases for 100 Myrs. A major result was
the appearance of an instability window at K = 5, where Mars escaped. This
new
result has important implications for the theories of the planetary system
formation process and mechanism. It is shown that with increasing K the
system
splits into two, well separated subsystems: one consists of the inner, the
other one consists of the outer planets. According to the results the model
became more stable as K increases and only when K >= 540 Mars escaped, on a
Myr
timescale. We found an interesting protection mechanism for Venus. These
results give insights also to the stability of the habitable zone of
exoplanetary systems, which harbour planets with relatively small
eccentricities and inclinations.

\\ ( http://arXiv.org/abs/astro-ph/0508670 , 630kb)

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\\
Paper: astro-ph/0508671
Date: Wed, 31 Aug 2005 09:10:52 GMT (354kb)

Title: Numerical simulations of type I planetary migration in nonturbulent
magnetized discs

Authors: Sebastien Fromang, Caroline Terquem, Richard P. Nelson

Comments: 17 pages, 12 figures, accepted in MNRAS. A version with full
resolution, colour figures is available at
http://www.maths.qmul.ac.uk/~rpn/preprints/
\\
Using 2D MHD numerical simulations performed with two different finite
difference Eulerian codes, we analyze the effect that a toroidal magnetic
field
has on low mass planet migration in nonturbulent protoplanetary discs. The
presence of the magnetic field modifies the waves that can propagate in the
disc. In agreement with a recent linear analysis (Terquem 2003), we find
that
two magnetic resonances develop on both sides of the planet orbit, which
contribute to a significant global torque. In order to measure the torque
exerted by the disc on the planet, we perform simulations in which the
latter
is either fixed on a circular orbit or allowed to migrate. For a 5 earth
mass
planet, when the ratio \beta between the square of the sound speed and that
of
the Alfven speed at the location of the planet is equal to 2, we find inward
migration when the magnetic field B_{\phi} is uniform in the disc, reduced
migration when B_{\phi} decreases as r^{-1} and outward migration when
B_{\phi}
decreases as r^{-2}. These results are in agreement with predictions from
the
linear analysis. Taken as a whole, our results confirm that even a
subthermal
stable field can stop inward migration of an earth--like planet.

\\ ( http://arXiv.org/abs/astro-ph/0508671 , 354kb)

• Previous message: LARRY KLAES: "SETI public: Planetesimal Formation without Thresholds I and II"

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