37th DPS Meeting, 4-9 September 2005
Session 25 Planet and Satellite Formation
Oral, Tuesday, September 6, 2005, 2:00-3:50pm, Law LG19

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[25.08] Embedded Star Clusters and the Formation of the Inner Oort Cloud

R. Brasser, M. J. Duncan (Queen's University), H. F. Levison (South-west Research Institute)

Observations suggest most stars originate in clusters embedded in giant molecular clouds (Lada & Lada 2003). Our Solar System likely spent 1-5 Myrs of its early stages in such regions so that the Oort Cloud possibly retains evidence of the Sun's early dynamical history.

The IOC's formation was studied by numerical simulations of the orbital evolution of comets subject to the influence of the Sun, Jupiter and Saturn with their current orbits and masses, passing stars and tidal force associated with the gas of an embedded star cluster. The cluster is a Plummer model, with a range of initial central densities. The Sun's orbit was integrated in the cluster potential together with the planets and test particles. Stellar encounters are incorporated by directly integrating the effects of stars passing within 5000 - 20000 AU, centred on the Sun, depending on cluster density. The influence of the gas is modeled using the tidal force of the cluster potential.

We present results of the IOC's structure resulting from different Solar orbits and cluster properties. For cluster central densities >~ 104 Msun pc-3, and plausible Solar orbits, ~5-20% of comets are in the IOC after 1-3 Myr. We define a comet as part of the IOC if it is bound, has q>15 AU and a>100 AU. Our models easily produce objects on Sedna-like orbits within 2 Myr and in cases where the central density is 105 Msun pc-3 or higher, orbits like that of 2000 CR105 are created too. Thus the latter object may be part of the IOC.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.