Analytic Approach to the Late Stages of Giant Planet Formation

TL;DR

This paper develops an analytic model for the late stages of giant planet formation, detailing the gas accretion process, disk properties, and radiative signatures, providing insights into the physical conditions and observational features during this critical phase.

Contribution

It introduces a comprehensive analytic framework for the late-stage accretion and disk structure of forming giant planets, including magnetic truncation effects and radiative signatures.

Findings

Derived steady-state surface density as a function of viscosity

Quantified the impact of magnetic fields on disk truncation

Explored the spectral energy distribution signatures of planet formation

Abstract

This paper constructs an analytic description for the late stages of giant planet formation. During this phase of evolution, the planet gains the majority of its final mass through gas accretion at a rapid rate. This work determines the density and velocity fields for material falling onto the central planet and its circumplanetary disk, and finds the corresponding column density of this infalling envelope. We derive a steady-state solution for the surface density of the disk as a function of its viscosity (including the limiting case where no disk accretion occurs). Planetary magnetic fields truncate the inner edge of the disk and determine the boundary conditions for mass accretion onto the planet from both direct infall and from the disk. The properties of the forming planet and its circumplanetary disk are determined, including the luminosity contributions from infall onto the planet and disk surfaces, and from disk viscosity. The radiative signature of the planet formation process is explored using a quasi-spherical treatment of the emergent spectral energy distributions. The analytic solutions developed herein show how the protoplanet properties (envelope density distribution, velocity field, column density, disk surface density, luminosity, and radiative signatures) vary with input parameters (instantaneous mass, orbital location, accretion rate, and planetary magnetic field strength).