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Project Progress

Astrophysical Constraints on Planet Formation (dm)

We have continued our exploration of planet formation in OB association star clusters (hot, young, massive stars). We have analyzed the colors of several protoplanetary disks in the Orion Nebula from 500 nm to 1870 nm. The translucent outer edge of the largest disk is achromatic, implying grains larger than 5 mm. We have also developed a model of grain growth in the presence of UV radiation induced photo-ablation.

We have shown that most young stars are born in either very over-dense but transient star clusters or in multiple star systems in which circumstellar disks may be truncated or destroyed by the close passage of nearest neighbor stars. Our best estimate is that only 3 to 10% of young stars will possess planetary systems. The rest of the stars lost their disks prematurely due to photo-ablation, dynamical interactions, or are in multiple star systems or bound clusters where planetary orbits may suffer large perturbations.