Exploring multiple generations of planetary embryos

¹ Max Planck Institute for Astronomy, Heidelberg, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: voelkel@mpia.de
² Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6 CH 3012 Bern, Switzerland
³ Universitäts-Sternwarte München, Ludwig-Maximilians-Universität München, Scheinerstraße 1, 81679 München, Germany

Received: 20 July 2021
Accepted: 2 February 2022

Abstract

Context. Global models of planet formation tend to begin with an initial set of planetary embryos for the sake of simplicity. While this approach gives valuable insights into the evolution of the initial embryos, the initial distribution itself is staked on a bold assumption. Limiting the study to an initial distribution may neglect essential physics that either precedes or follows such an initial distribution.

Aims. We wish to investigate the effect of dynamic planetary embryo formation on the formation of planetary systems.

Methods. The presented framework begins with an initial disk of gas, dust, and pebbles. The disk evolution, the formation of plan-etesimals and the formation of planetary embryos is modeled consistently. Embryos then grow by pebble accretion, followed by planetesimal and, eventually, gas accretion. Planet-disk interactions and N-body dynamics, along with a consideration of other simultaneously growing embryos, are included in the framework.

Results. We show that the formation of planets can occur in multiple consecutive phases. Earlier generations grow massive by pebble accretion but are subject to fast type I migration and, thus, by accretion to the star. The later generations of embryos that form grow too much smaller masses by planetesimal accretion, as the amount of pebbles in the disk has vanished.

Conclusions. The formation history of planetary systems may be far more complex than an initial distribution of embryos could reflect. The dynamic formation of planetary embryos needs to be considered in global models of planet formation to allow for a complete picture of the system’s evolution.