Formation of Giant Planets

TL;DR

Giant planets, primarily composed of hydrogen and helium with enriched heavy elements, form through core accretion or disk instability, influencing planetary system architecture and composition.

Contribution

This paper reviews the main models of giant planet formation, including core accretion and disk instability, highlighting their roles and differences.

Findings

Core accretion is a primary formation mechanism.

Disk instability may form planets on wide orbits.

Giant planets significantly influence planetary system architecture.

Abstract

Giant planets are tens to thousands of times as massive as the Earth, and many times as large. Most of their volumes are occupied by hydrogen and helium, the primary constituents of the protostellar disks from which they formed. Significantly, the solar system giants are also highly enriched in heavier elements relative to the Sun, indicating that solid material participated in their assembly. Giant planets account for most of the mass of our planetary system and of those extrasolar planetary systems in which they are present. Therefore, giant planets are primary actors in determining the orbital architectures of planetary systems and, possibly, in affecting the composition of terrestrial planets. This Chapter describes the principal route that, according to current knowledge, can lead to the formation of giant planets, the core nucleated accretion model, and an alternative route, the disk instability model, which may lead to the formation of planetary-mass objects on wide orbits.