Reshaping the outskirts of planetary systems

Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain

Corresponding author: C. de la Fuente Marcos, nbplanet@eucmos.sim.ucm.es

Received: 31 October 2000
Accepted: 12 March 2001

Abstract

We present N-body calculations of the orbital evolution of a test population of primordial Edgeworth-Kuiper Belt objects (EKBOs) in a star cluster submitted to the gravitational perturbations of other cluster members, both single stars and binaries. In order to provide initial conditions for the EKBO test population, three original orbital distributions (eccentricity and semi-major axis) are considered. The first resembles a conventional model of the evolution of the solar nebula with eccentricity, e = 0.01 and semi-major axis uniformly distributed in the range 35-60 AU. The second distribution considers the stage of planet formation after Neptune's outward migration with concentration of solid particles at 39 AU and . The third distribution is taken from a non-collisional, two-dimensional simulation of a gaseous protoplanetary disk in which solid particles beyond 60 AU are perturbed by the growing proto-planets, Uranus and Neptune. Metric particles are trapped in an outer resonance with radial distance of about 48.5 AU and eccentricity of 0.16. Stellar encounters lead to significant modification of the primordial orbital distribution only if the Sun was born in a typical open cluster but not in an association. Our results suggest that the observed orbital distribution of the scattered EKBOs may be the result of these multi-body gravitational interactions in the Sun's parent star cluster. On the other hand, the circular shape of the Edgeworth-Kuiper Belt-like structure found around ϵ Eridani indicates that this star was born in a small cluster or association.