The Renaissance in Solar System Dynamics

Monday, October 29, 2001 - 9:30am - 10:30am
Keller 3-180
Joseph Burns (Cornell University)
Four decades ago, at the dawn of the space age, the solar system was viewed as static. This talk will show why and how that view has been overturned. Major advances have been made in understanding the solar system's structure and its cause owing to provocative data provided by spacecraft and ground observatories, new algorithms coupled with improved and widely accessible computers that have allowed extraordinarily long orbit integrations, and new paradigms from dynamical systems.

No longer is the solar system thought to be a fixed, deterministic entity. Dissipation (by tides, drags and anelasticity) is now known to have profoundly modified the solar system: rotations damp into pure spins while orbits evolve significantly, occasionally leading to the loss of past objects through collisions. Resonances (two- or three-body mean-motion as well as secular resonances) play a major role in the solar system's current structure. Objects that drift into resonant orbits may become trapped at these positions, sometimes protecting themselves, but may also suffer substantial jumps in orbital eccentricity and inclinations, which allow orbits to cross at high speeds. Many orbits were--and are--chaotic. In total, dissipation, close-interactions and chaos have reconfigured the solar system, ejecting many objects to interstellar space, causing some to collide and transmuting yet others from comets to asteroids.

Rotations have also evolved over the eons: Mercury is locked in a 3:2 spin-orbit resonance while Venus' spin may not be tidally damped; Mars undergoes substantial obliquity oscillations that may have markedly influenced its climatic history; Saturn's satellite Hyperion tumbles chaotically and other irregular moons may have, with important thermal consequences. The rotations of asteroids are intimately tied to the collisional histories of the minor planets; some spin extraordinarily slowly, others remarkably fast, even a few wobble noticeably like comet Halley. Planetary rings form a rich dynamical laboratory, exhibiting a bewildering array of phenomena: bending and spiral density waves at resonances; satellite perturbations, including shepherding and clumping; angular momentum transfer through collisions; spokes; and electromagnetic interactions.

The behavior of planets and disks around other stars is just beginning to be explored and should produce many interesting models to be interpreted by the techniques of dynamical systems.