TIDALLY INDUCED BROWN DWARF AND PLANET FORMATION IN CIRCUMSTELLAR DISKS
- Argelander-Institut fuer Astronomie (Sternwarte), Universitaet Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany)
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)
- School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom)
Most stars are born in clusters and the resulting gravitational interactions between cluster members may significantly affect the evolution of circumstellar disks and therefore the formation of planets and brown dwarfs (BDs). Recent findings suggest that tidal perturbations of typical circumstellar disks due to close encounters may inhibit rather than trigger disk fragmentation and so would seem to rule out planet formation by external tidal stimuli. However, the disk models in these calculations were restricted to disk radii of 40 AU and disk masses below 0.1 M{sub sun}. Here, we show that even modest encounters can trigger fragmentation around 100 AU in the sorts of massive ({approx}0.5 M{sub sun}), extended ({>=}100 AU) disks that are observed around young stars. Tidal perturbation alone can do this; no disk-disk collision is required. We also show that very low mass binary systems can form through the interaction of objects in the disk. In our computations, otherwise non-fragmenting massive disks, once perturbed, fragment into several objects between about 0.01 and 0.1 M{sub sun}, i.e., over the whole BD mass range. Typically, these orbit on highly eccentric orbits or are even ejected. While probably not suitable for the formation of Jupiter- or Neptune-type planets, our scenario provides a possible formation mechanism for BDs and very massive planets which, interestingly, leads to a mass distribution consistent with the canonical substellar initial mass function. As a minor outcome, a possible explanation for the origin of misaligned extrasolar planetary systems is discussed.
- OSTI ID:
- 21452859
- Journal Information:
- Astrophysical Journal, Vol. 717, Issue 1; Other Information: DOI: 10.1088/0004-637X/717/1/577; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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