Sur la stabilité gravitationnelle d'une nébuleuse isotherme

This paper deals with the gravitational stability of an isothermal nebula stratified in plane parallel layers symmetrical with respect to a central plane of density p0. It is shown that JEANS' criterion is still valid provided that one takes for the density which appears in it, the value p0 /2. This justifies the use made by G.P. KUIPER of JEANS' criterion in his discussions of the origin of the solar system. More generally, a preliminary condensation of nebulous mutter according to this model might help in the formation by gravitational instability of smaller condensations then hitherto possible.