Published online by Cambridge University Press: 25 April 2016
When the separation between two stars becomes sufficiently small, tidal forces may cause one or both stars to disrupt. Roche (1850) studied the problem of the stability of a liquid in synchronous, circular orbit with a point mass, and predicted an instability of the liquid star for separations ≤ 2.5 r S⅓ where R is the initial radius of the liquid star, and S is the ratio of the mass of the point to the mass of the liquid star. Darwin generalized the problem to allow for two liquid stars in circular orbit. The whole of the classical research has been systematically analysed by Chandrasekhar (1969) using the tensor virial method. An error in Chandrasekhar’s analysis was corrected by Tassoul (1975).