Heidelberg 1999 – wissenschaftliches Programm

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PV: Plenarvorträge

PV XIV

PV XIV: Plenarvortrag

Freitag, 19. März 1999, 09:00–09:45, CH 1

Chaotic behavior and organisation of the Solar System — •Jacques Laskar — Astronomie et Systèmes Dynamiques, CNRS–Bureau des Longitudes, 77 av. Denfert–Rochereau, F75014 Paris, France, email: laskar@bdl.fr

Until very recently, the Solar System was considered as the model of regularity. In fact, the numerical experiments conducted in the past few years reveal the contrary.

Although the motion of the large planets is very close to quasiperiodic, the motion of the small planets (Mercury, Venus, the Earth, Mars and Pluto) is chaotic. The chaotic diffusion of the orbits of Venus and the Earth is sensible. The diffusion of the orbit of Mars can increase its eccentricity up to 0.25, while the unstabilities in the orbit of Mercury are so large that this planet can probably cross the orbit of Venus within 5 billion years.

Using the maximum possible evolution of the orbits over 5 billion years, it was possible to show that the inner Solar System is full, which mean that the zones swept by each planet at their maximum eccentricity practically covers the full space, not allowing the presence of any additional body in the inner Solar System over long time span. This constatation leads to the idea of marginal stability for the Solar System, that is the Solar System is not regular, but strong unstabilities, leading to the disruption of the system can only occur in time span comparable to its age. This also shows that in an earlier stage, other bodies could have existed, but the system would be much more unstable, which would lead to the rapid escape or collision of one of the bodies. After a collision, the remaining system should become much more stable.