Gravitational Instability in Binary Protoplanetary Disks

Abstract

Gravitational instabilities (GIs) can occur in any region of a gas disk that becomes sufficiently cool or develops a high enough surface density. In the nonlinear regime, GIs can produce local and global spiral waves, self-gravitating turbulence, mass and angular momentum transport, and disk fragmentation into dense clumps and substructure. It has been quite some time since the idea was first suggested by Kuiper (1951) and Cameron (1978), and revived by Boss (1997, 1998) stating that the dense clumps in a disk fragmented by GIs may become self-gravitating precursors to gas giant planets. This particular idea for gas giant planet formation has come to be known as the disk instability theory. The idea is appealing since gravitational instability develops on very short timescales compared to the accumulation of planetesimals by gravity and the subsequent accretion of gas by a rocky core, the conventional two-stage giant planet formation theory known as core accretion (see the chapter by Marzari et al.).