Formation of Jupiter by nucleated instability

Recently it has been shown that long-lasting self-gravitating protoplanets can arise from a gravitationally unstable protoplanetary gaseous disks (Mayer et al., 2002). We are convinced that these calculations are extremely important to explain the existence of large extrasolar planets. Here we adopted a different approach, using as a reference scenario, the nucleated instability. This process takes place when the nebular gas is collected by an already formed solid core. This paper describes a long lasting project that simulates the formation of giant planets implementing the gas accretion onto the core via a 3-D hydro-dynamical model, recently developed in its present version (Magni and Coradini, 2003). Here we describe the structure of the central planet, while in a further paper we will treat the disk formation where possibly satellites were formed. To study the planet structure and the gas surrounding it we have considered three main regions: the central planet, a turbulent accretion disk which surrounds it and an extended region from which the gas is collected. The strong interaction between the growing planet and the surrounding gas warms the gas, creating a “barrier” that tends to reduce the accretion rate. The planetʹs thermodynamic structure depends upon the mass accretion rate onto it. The gas also exchanges angular momentum with the central body. Particular attention in the model has been paid to the analysis of angular momentum distribution between the growing planet and the disk. This work shows that we can match Jupiter present angular momentum.