An Etymological Dictionary of Astronomy and Astrophysics

An instability that occurs in a → self-gravitating  → interstellar cloud which is in → hydrostatic equilibrium. Density fluctuations caused by a perturbation may condense the material
leading to the domination of gravitational force
and the cloud collapse. The advent of instability involves a threshold called the → Jeans length or the → Jeans mass.

See also: → Jeans; → instability.