Dust-Gas Instabilities in Protoplanetary Disks: Toward Understanding Planetesimal Formation

This book explores the formation of planetesimals, kilometer-sized bodies that precede planets, through disk instabilities. It addresses how instabilities evolve and presents a new instability driven by dust coagulation. The simulation demonstrates a scenario of planetesimal formation in dusty rings.

Format: Hardback
Length: 116 pages
Publication date: 26 April 2022
Publisher: Springer Verlag, Singapore

The formation of planets is a longstanding and complex topic in astrophysics, particularly when it comes to planetesimals, which are kilometer-sized bodies that are believed to be the precursors of planets. Despite the existence of some promising mechanisms, the exact formation scenarios of planetesimals remain unclear and are subject to ongoing debate. In this book, we focus on disk instabilities, which are believed to play a crucial role in the formation of planetesimals. By employing linear analyses and numerical simulations, we explore how a disk evolves through the development of instabilities and introduce a new instability driven by dust coagulation. Through these simulations, we demonstrate a scenario of planetesimal formation: a sequential progression of multiple instabilities leads to the formation of dusty rings, which eventually give rise to planetesimals.

Disk instabilities are crucial in understanding the formation of planetesimals because they provide a mechanism for the growth and aggregation of dust particles. When a disk is subjected to gravitational perturbations or other factors, such as turbulence or magnetic fields, it can develop regions of high density and low density. These regions, known as density waves or spiral arms, can collide and merge, leading to the formation of clumps of dust. These clumps can then grow through the accretion of more dust particles, eventually reaching sizes that are large enough to attract other objects, such as gas giants or protoplanets.

One of the most promising mechanisms for planetesimal formation is the instability driven by dust coagulation. This instability occurs when small dust particles collide and stick together, forming larger aggregates. The growth of these aggregates can be driven by several factors, including gravitational forces, electromagnetic forces, and thermal forces. Once the aggregates reach a certain size, they can become unstable and collapse, forming planetesimals.

The simulation presented in this book demonstrates a scenario of planetesimal formation that is driven by multiple instabilities. The initial state of the disk is characterized by a smooth, rotating disk with a uniform density distribution. As the disk evolves, several instabilities develop, including the spiral instability, the Kelvin-Helmholtz instability, and the dust coagulation instability. These instabilities trigger the formation of dusty rings, which eventually collapse and give rise to planetesimals.

The simulation results show that the formation of planetesimals is a complex process that involves the interaction of multiple instabilities and physical processes. The formation of dusty rings is a gradual process that takes place over millions of years, as the disk evolves through the development of instabilities and the accretion of dust particles. The final state of the disk is characterized by the presence of multiple planetesimals, which are still in the process of growing and aggregating.

In conclusion, the formation of planets is a complex and challenging topic in astrophysics, particularly when it comes to planetesimals. Disk instabilities, particularly the instability driven by dust coagulation, provide a promising mechanism for the formation of planetesimals. By employing linear analyses and numerical simulations, we can explore how a disk evolves through the development of instabilities and demonstrate a scenario of planetesimal formation. This research has the potential to shed light on the early stages of planet formation and help us better understand the origins.

Weight: 366g
Dimension: 235 x 155 (mm)
ISBN-13: 9789811917646
Edition number: 1st ed. 2022