From Disks to Planets

TL;DR

This chapter provides a comprehensive overview of planet formation theories, including disk evolution, planetesimal growth, atmosphere accretion, and direct gas disk fragmentation, integrating empirical data and current research insights.

Contribution

It offers an updated pedagogical synthesis of physical processes in planet formation, emphasizing recent research developments and contrasting different formation scenarios.

Findings

Protoplanetary disk structures and evolution are summarized.

Growth processes from planetesimals to protoplanets are detailed.

Multiple pathways for giant planet formation are discussed.

Abstract

This pedagogical chapter covers the theory of planet formation, with an emphasis on the physical processes relevant to current research. After summarizing empirical constraints from astronomical and geophysical data, we describe the structure and evolution of protoplanetary disks. We consider the growth of planetesimals and of larger solid protoplanets, followed by the accretion of planetary atmospheres, including the core accretion instability. We also examine the possibility that gas disks fragment directly into giant planets and/or brown dwarfs. We defer a detailed description of planet migration and dynamical evolution to other work, such as the complementary chapter in this series by Morbidelli (available at arXiv:1106.4114).