LABORATOIRE CASSIOPÉE - O. C. A.

Séminaire

Phénomènes Physiques et Modèles Mathématiques en Sciences de l'Univers

Le séminaire a lieu le vendredi 15 décembre 2005 de 11h00 à 12h00
dans la salle de réunion du PHC (Observatoire de Nice). 

The web of three-planet resonances in the outer solar system:

a source of slow orbital instability for Uranus and Neptune

M . Guzzo

 Universita di Padova, Italia

The motion of the giant planets from Jupiter to
Neptune is chaotic with Lyapunov time of approximately 10 Myr. A recent
theory explains the presence of this chaos with three-planet mean--motion
resonances, i.e. resonances among the orbital periods
of at least three planets. I will show that the distribution of these
resonances with respect to the semi-major axes of all the planets
is compatible with orbital instability. In particular, they
overlap in a region of 10**(-3) AU with respect
to the variation of the semi-major axes of Uranus and Neptune. Fictitious
planetary systems with initial conditions in this region can undergo
systematic variations of semi-major axes. The true Solar System is
marginally in this region, and Uranus and Neptune undergo very slow
systematic variations of semi--major axes with approximate speed of
order 10**(-4) AU/Gyr.