Dust grain growth and settling time inside initial gaseous giant protoplanets in the mass range 0.3 to 5 Jovian masses, formed by gravitational instability, have been investigated. We have determined the distribution of thermodynamic and physical variables inside the protoplanets solving the structure equations assuming their gas blobs to be fully convective and with this distribution we have calculated growth and settling time of grains with different initial sizes (10 −2 cm ≤ r 0 ≤ 1 cm). The results of our calculations are found to be in good agreement with those obtained by different approaches.

Segregation problem of individual molecules of heavy elements, has been reinvestigated determining the polytropic structure of a protoplanet. In this study the sedimentation time of different silicate grains having radii lying between 5 X 10-3cm and 1 cm was calculated. Settling times of the grains that came out through calculation could be found to be shorter than that of the time obtained by other authors. Key words: Segregation; Grain; Gravitational field; Protoplanet; Polytrope DOI: http://dx.doi.org/10.3329/jbas.v35i2.9422 JBAS 2011; 35(2): 179-186