Perturbations on an extended Kuiper disk caused by passing stars and giant molecular clouds.

BRUNINI, A.; FERNANDEZ, J. A.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 1996 vol. 308 p. 988 - 994

0004-6361

We assess the importance of stellar and giant molecular cloud perturbations on extended Kuiper-like disks. We integrate numerically the equations of motion assuming circular orbits for the test Kuiper-disk particles and that the external perturber (either a star or a GMC) moves on a straight path. GMCs are modeled as very diffuse structures with a few dense clumps of 10^3^Msun_, so the bulk of a GMC perturbation is assumed to arise from the sum of the contributions of independent encounters with the dense clumps. We find that external perturbers can induce eccentricities of about 0.04-0.08 over the solar system age on Kuiper-disk objects in initially circular orbits of radii 100-500AU. Relative changes of the semimajor axis are of the same order, thus allowing radial excursions of some tens AU. This migh have important consequences in the accretion process and in the collisional evolution of Kuiper-disk members. Furthermore, due to small radial excursions, Kuiper-disk objects closer to the planetary region can be injected into chaotic zones. Changes in the orbital inclinations are of a few degrees, thus having little consequence on the flattened structure of the disk. Perturbations by GMCs are found to be much smaller than those caused by passing stars. Yet, the much faster increase of the GMC perturbations with the semimajor axis, ensures that they will become dominant at Oort cloud distances, in agreement with some previous results by different authors. We find a non-zero probability (a few tenths percent) of dynamical disruption of the outer portions of circumstellar disks (say at radii >500AU) over the solar system age.