Aerodynamics of solid bodies in the solar nebula

TLDR

In a centrally condensed solar nebula, gas pressure gradients slow rotation relative to free orbital velocity, and drag forces cause solid bodies’ orbits to decay. The authors investigated solid-body motions analytically and numerically across all applicable drag laws and presented results for a variety of model nebulae. The study finds that maximum radial velocity is independent of drag law and nebular mass, but strongly depends on particle size, reaching ~10⁴ cm/s for metre-sized objects, implying rapid mixing, planetesimal accumulation, size/density fractionation, and anomalous composition regions.

Abstract

In a centrally condensed solar nebula, the pressure gradient in the gas causes the nebula to rotate more slowly than the free orbital velocity. Drag forces cause the orbits of solid bodies to decay. Their motions have been investigated analytically and numerically for all applicable drag laws. The maximum radial velocity developed is independent of the drag law, and insensitive to the nebular mass. Results are presented for a variety of model nebulae. Radial velocities depend strongly on particle size, reaching values on the order of 104 cm/s for metre-sized objects. Possible consequences include: mixing of solid matter within the solar nebula on short timescales, collisions leading to rapid accumulation of planetesimals, fractionation of bodies by size or density, and production of regions of anomalous composition in the solar nebula.