Simultaneous formation of solar system giant planets

Abstract

Context. In the last few years, the so-called "Nice model" has become increasingly significant for studying the formation and evolution of the solar system. According to this model, the initial orbital configuration of the giant planets was much more compact than the one we observe today. Aims. We study the formation of the giant planets in connection with several parameters that describe the protoplanetary disk. We aim to establish which conditions enable their simultaneous formation in line with the initial configuration proposed by the Nice model. We focus on the conditions that lead to the simultaneous formation of two massive cores, corresponding to Jupiter and Saturn, which are able to reach the cross-over mass (where the mass of the envelope of the giant planet equals the mass of the core, and gaseous runway starts), while two other cores that correspond to Uranus and Neptune have to be able to grow to their current masses. Methods. We compute the in situ planetary formation, employing the numerical code introduced in our previous work for different density profiles of the protoplanetary disk. Planetesimal migration is taken into account and planetesimals are considered to follow a size distribution between r min p (free parameter) and r max p = 100 km. The core's growth is computed according to the oligarchic growth regime.Results. The simultaneous formation of the giant planets was successfully completed for several initial conditions of the disk. We find that for protoplanetary disks characterized by a power law (Σ ∝ r −p ), flat surface density profiles (p ≤ 1.5) favor the simultaneous formation. However, for steep slopes (p ∼ 2, as previously proposed by other authors) the simultaneous formation of the solar system giant planets is unlikely. Conclusions. The simultaneous formation of the giant planets -in the context of the Nice model -is favored by flat surface density profiles. The formation time-scale agrees with the estimates of disk lifetimes if a significant mass of the solids accreted by the planets is contained in planetesimals with radii <1 km.

The PLATO 2.0 mission

“…This contraction triggers a very rapid accretion of gas, which is limited by the amount of gas that can be delivered by the protoplanetary disk surrounding the forming planet. This scenario has been studied by many authors, accounting for different physical effects, like protoplanet migration (Alibert et al 2004(Alibert et al , 2005, opacity reduction in the planetary envelope (e.g., Hubickyj et al 2005), excitation of accreted planetesimals by forming planets (e.g., Fortier et al 2007Fortier et al , 2013, competition between different planets (e.g., Guilera et al 2011). …”

Planetesimal fragmentation and giant planet formation

“…Our model that describes the evolution of the protoplanetary disk is based on the works of Guilera et al (2010Guilera et al ( , 2011 with some minor improves incorporated. We used an axisymmetric protoplanetary disk characterized by a gaseous and a solid component.…”

“…In previous works (Guilera et al 2010(Guilera et al , 2011 we developed a model for giant planet formation that calculates their formation Article published by EDP Sciences A96, page 1 of 14 immersed in a protoplanetary disk that evolves in time. In these previous works the population of planetesimals evolved by the accretion of the embryos and by planetesimal migration.…”

Terrestrial planets in high-mass disks without gas giants

“…Thommes et al (2003), Chambers (2006), and Guilera et al (2010Guilera et al ( , 2011 showed that this effect has important consequences on the timescale of planetesimal accretion and in the planetesimal surface density evolution, especially for small bodies (r p 1 km). As a consequence of the conservation of mass, the planetesimal surface density obeys a continuity equation.…”