The Gas Drag Effect on the Elliptic Motion of a Solid Body in the Primordial Solar Nebula
The gas drag effect in the primordial solar nebula on the motion of a solid body, ranging from a large planetesimal to a small dust grain, is investigated. For a planetesimal, expressions for the short-term variation of the semi-major axis, the eccentricity and inclination are obtained using a perturbation method and a realistic formula for the gas drag force. For a small body, an orbit spiralling towards the sun in the equatorial plane of the nebula is investigated and the decay time of the orbital radius is obtained. It is found that the decay time at 1 a.u. is as short as 102 or 103 years for a solid body with mass in the range between 103 g and 108 g.