Modeling and simulations of protoplanetary dynamics and chaotic interactions of planetesimals

Since the discovery of planets orbiting stars other than our own Sun, the study of the formation of planets and planetary systems has become a popular topic in astrophysics. Most theories about how planets are created are involved with the creation and dynamical evolution of small solid objects known as planetesimals, which are formed in orbit around a star during the earlier stages of its life. These theories are now being reconsidered in light of observations of extrasolar planets, which are seen to be quite different from the nine with we are most familiar.; It is also known that physical systems with large numbers of bodies (such as planetary systems) are chaotic in nature, meaning that they are very sensitive to slight changes in their initial conditions. The connections between chaos theory and protoplanetary dynamics are not fully understood, but may prove vital in explaining the diversity of observed phenomena both in extrasolar planetary systems and in our own Solar System.; A series of computer simulations representing protoplanetary disks containing hundreds of planetesimals were performed using a fifth-order Runge-Kutta integrator to investigate the effects of mutual gravitational interactions inherent in protoplanetary systems. Under various conditions, the overall development of the planetesimal system could be studied as it evolved in time. It was shown that rings of planetesimals are more stable (except for a slow diffusion and some rare scattering events) without protoplanets than with them.; Larger protoplanets were also introduced to determine their influence on the system. The results were then examined to determine how the protoplanets and planetesimals affected one another, and what kinds of planetary systems could evolve. Protoplanets were observed to induce lane clearing and higher rates of collisions, which are essential in determining the possible locations and growth rates of other protoplanets that could form within the system at a later time. They also affected scattering processes, creating structures similar to the Kuiper belt and Centaur-class comets seen within the Solar System. The reaction on the protoplanets themselves produced effects such as oscillations in their orbital elements that became chaotic when the gravitational interactions were strong enough, and, in some rare cases, migration of the protoplanets. Migration processes have become very important in explaining the properties of observed extrasolar planets.