Formation of terrestrial planets in disks evolving via disk winds and implications for the origin of the solar system’s terrestrial planets

Abstract

Context. Recent three-dimensional magnetohydrodynamical simulations have identified a disk wind by which gas materials are lost from the surface of a protoplanetary disk, which can significantly alter the evolution of the inner disk and the formation of terrestrial planets. A simultaneous description of the realistic evolution of the gaseous and solid components in a disk may provide a clue for solving the problem of the mass concentration of the terrestrial planets in the solar system. Aims. We simulate the formation of terrestrial planets from planetary embryos in a disk that evolves via magnetorotational instability and a disk wind. The aim is to examine the effects of a disk wind on the orbital evolution and final configuration of planetary systems. Methods. We perform N-body simulations of sixty 0.1 Earth-mass embryos in an evolving disk. The evolution of the gas surface density of the disk is tracked by solving a one-dimensional diffusion equation with a sink term that accounts for the disk wind. Results. We find that even in the case of a weak disk wind, the radial slope of the gas surface density of the inner disk becomes shallower, which slows or halts the Type I migration of embryos. If the effect of the disk wind is strong, the disk profile is significantly altered (e.g., positive surface density gradient, inside-out evacuation), leading to outward migration of embryos inside ∼1 AU. Conclusions. Disk winds play an essential role in terrestrial planet formation inside a few AU by changing the disk profile. In addition, embryos can undergo convergent migration to ∼1 AU in certainly probable conditions. In such a case, the characteristic features of the solar system's terrestrial planets (e.g., mass concentration around 1 AU, late giant impact) may be reproduced.

Dispersal of protoplanetary discs by the combination of magnetically driven and photoevaporative winds

“…Observations have revealed that the typical lifetime of protoplanetary disks is several million years (Myr) (e.g., Haisch et al 2001;Mamajek 2009;Yasui et al 2010;Takagi et al 2014). Their evolution and dispersal is crucial for the planet formation in protoplanetary disks: for example, the growth of solid particles and the migration of (proto)planets depend on the disk properties (e.g., Matsuyama et al 2003;Ogihara et al 2015;Kobayashi & Tanaka 2018).…”

A reassessment of the in situ formation of close-in super-Earths

“…However, no mechanism capable of suppressing Type I migration over the whole inner disk has ever been found. Recent studies have shown that MRI-driven disk winds, in which gas material is blown away from the surface of the disk, can alter the density profile of the gas disk, potentially slowing down or even reversing the migration of the protoplanets (e.g., Suzuki & Inutsuka 2009;Suzuki et al 2010;Ogihara et al 2015). This possibility, however, requires further investigation.…”

“…Each formula is given by Eqs. (11)−(13) in Ogihara et al (2015). In addition, the corotation torque decreases as the planet eccentricity increases (e.g., Bitsch & Kley 2010).…”

The Galilean Satellites Formed Slowly from Pebbles

“…v K ,(28)where b t1 is the migration constant, which depends on the distribution of the temperature and gas surface density of the CJD (see Eq. (10) ofOgihara et al (2015)). If b t1 is negative or positive, the satellite migrates inward or outward, respectively.…”