The Development of Gravitational Instability in a Self-Gravitating Gas Cloud.

The prnblem discussed is that of the way in which subcondensations can form in a large, gravft tionally unstable, spherical cloud. After reaching an unstable state, the cloud tends to collapse syn metrically, though a linearized perturbation analysis of the symmetric collapse shows this motion to unstable. Subcondensations form against the background of the over-all collapse of the cloud, once th over-all collapse has got well under way. This instability is caused by the self-gravitational forces exerte by the perturbations themselves. Effects which depend on non-linear terms in the governing equatior are also discussed. The rotation of fluid elements is considered as a possible mechanism by which t breakup of the cloud into subcondensations can be halted, but it is argued that this mechanism is n( effective, except under rather special initial conditions. The linearized perturbation analysis is also e tended by the evaluation of second-order terms in the perturbation expansion, and some implications these are discussed.