An Etymological Dictionary of Astronomy and Astrophysics

1. General: The process by which an → accretion disk cools, causing it to fragment into self-gravitating → clumps.
   

2. A model of → planet formation in which a region of a → circumstellar disk becomes dense and cool enough to be unstable to → gravitational collapse, resulting in the formation of a gaseous → protoplanet. Disk instability
   has been put forward as a mechanism for forming massive → giant planets on short time-scales (1 Ky-1 My).
   

3. In models of galactic structure, a process that is thought to cause the formation of → pseudo-bulges.
   

4. → disk instability model (DIM).

See also: → disk; → instability.