Orbit Evolution of Planetary Systems in Stellar Clusters

10/2003; 294:217-220.

ABSTRACT Stars and with them their planetary system are generally formed in star
clusters. Dynamical interaction between stars in clusters affects the
stability and dynamical evolution of their companion planetary systems.
We study systematically the statistical evolution of planetary orbit
parameters self-consistently with the evolution of their parent star
cluster using direct high-accuracy N-body simulations.

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    ABSTRACT: We consider the survivability of planetary systems in the globular cluster 47 Tucanae. We compute the cross sections for the breakup of planetary systems via encounters with single stars and binaries. We also compute the cross sections to leave planets on eccentric orbits. We find that wider planetary systems (d > 0.3 AU) are likely to be broken up in the central regions of 47 Tucanae (within the half-mass radius of the cluster). However tighter systems, and those in less-dense regions may survive. Tight systems will certainly survive in less-dense clusters where subsequent surveys should be conducted. Comment: 6 pages, 4 figures; accepted for MNRAS
    Monthly Notices of the Royal Astronomical Society 04/2001; 324(3). DOI:10.1046/j.1365-8711.2001.04336.x · 5.11 Impact Factor
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    ABSTRACT: The discovery of an ejected-planet candidate in a young star cluster in the Taurus Molecular Cloud suggests that ejection of planets is possible in star clusters. Here we consider the possibility that runaway planets are a common occurrence in star clusters. We follow the evolution of several N-body models of star clusters (N≤2500) with a population of mono-planetary systems and calculate the probability of ejection. This probability lies in the range from 0% to 3% with a mean value of about 1.5%, depending on the distribution of semi-major axes of the planetary systems. The results seem to be not dependent of the population of the cluster. Two main processes can contribute to planet ejection in star clusters: dynamical ejection and supernova driven ejection. This work is restricted to the study of the dynamical-ejection mechanism although some conclusions on the supernova mechanism are also pointed out. The mechanism by which these dynamically ejected runaways occur requires the formation of a hierarchical system in the cluster. It has been found that ejected planets have a maximum velocity of , and a mass-velocity relation in which the most massive planets tend to have higher velocities. In the light of our calculations, TMR-1C seems to be a clear case of ejection after collision at pericenter of a hierarchical system. We conclude that the spatial density of nomadic planets ejected from star clusters must be very low and that the ejection process from the interaction with stellar neighbors inside the cluster is not dominant. Nomadic planets generated by this mechanism make a very negligible contribution to the overall mass density of the Galaxy.
    New Astronomy 02/1999; 4(1-4):21-32. DOI:10.1016/S1384-1076(98)00043-8 · 1.15 Impact Factor


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