Photophoresis: Potential Sorting Mechanism in a Proto-planetary Disk




Smallwood, Jeremy

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The details of planet formation are still largely unknown, but it is understood that the initial stage of planet formation depends primary on the coagulation of micron-sized dust grains. One of the unexplained observations is that the density of the planets in our solar system decreases with increasing distance from the sun. One mechanism that could be responsible for this phenomenon is the photophoretic force, which arises when dust grains in low pressure environments are unevenly heated from an illumination source. The trajectories of rotating and non-rotating dust aggregates were modeled under the influence of photophoresis. The drift velocity of aggregates subject to the photophoretic force is determined by calculating the momentum transferred as gas molecules collide with and are re-emitted from the surface. For short simulation times, rotating aggregates have a weaker photophoretic force than non-rotating aggregate but the percentage difference is only 0.3%. The change in photophoretic force for rotating aggregates seems to be negligible when the aggregate is rotating around the direction of illumination.



Early Planet Formation