Modeling the formation of a giant planet with collisions among planetesimals

GUILERA, O.; SAN SEBASTIAN, IRINA L.; PARISI, M. G.

Santiago

Workshop; Diversis Mundi: The Solar System in an Exoplanetary context, an ESO Workshop; 2018

European Southern Observatory ESO

The formation of a giant planet must be completed within the protoplanetary disk lifetime  106 - 107 yrs. In the core instability scenario, the core Mc of a giant planet is formed by accreting solids, which might be planetesimals and/or pebbles. Once Mchas grown enough its gravity allows a slow gas accretion until the mass of the gaseous envelope Mg equals that of the core Mc and then, Mc is called Mcross, the crossing mass. After Mcross is reached, the planet may accrete gas in a runaway phase if gashas not yet dissipated. When gas accretion is finished, the planet cools and its envelope contracts. The key factor in the timescale of giant planet formation is Mc, which is a function of several parameters, such as the relative velocity of the planetesimals                                                                                                                                                                with respect to the protoplanet and the fragmentation of planetesimals due to collisions among them, which is a function of their relative velocity vrel and their impact specificenergy Q . In this work, we study the formation of a giant planet at 5 AU incorporating in our fragmentation model, the dependence of Q with the material properties and with vrel , where the accretion of pebbles of second generation is also included.                                                                                                                               In addition, new expressions for the relative velocities which are valid for high values of (e, i) are obtained, since vDS and vrel are usually expressed as a function of the planetesimals orbital eccentricity e and inclination i assuming (e, i) small.