Constraint on the giant planet production by core accretion

Abstract

The issue of giant planet formation by core instability (CI) far from the central star is rather controversial because the growth of massive solid core necessary for triggering the CI can take longer than the lifetime of the protoplanetary disk. In this work we assess the range of separations at which the CI may operate by (1) allowing for arbitrary (physically meaningful) rate of planetesimal accretion by the core and (2) properly taking into account the dependence of the critical mass for the CI on the planetesimal accretion luminosity. This self-consistent approach distinguishes our work from similar studies in which only a specific planetesimal accretion regime was explored and/or the critical core mass was fixed at some arbitrary level. We demonstrate that the largest separation at which the CI can occur within 3 Myr corresponds to the surface density of solids in the disk higher than 0.1 g cm^{-2} and is 40-50 AU in the minimum mass Solar nebula. This limiting separation is achieved when the planetesimal accretion proceeds at the fastest possible rate, even though the high associated accretion luminosity increases the critical core mass delaying the onset of the CI. Our constraints are independent of the mass of the central star and vary only weakly with the core density and its atmospheric opacity. We also discuss various factors which can strengthen or weaken our limits on the operation of the CI.