DOES THE MOMENTUM FLUX GENERATED BY GRAVITATIONAL CONTRACTION DRIVE ASYMPTOTIC GIANT BRANCH MASS-LOSS

Gravitational contraction always generates a radially directed momentu m flow. A particularly simple example occurs in the electron-degenerat e cores of asymptotic giant branch (AGB) stars, which contract steadil y under the addition of helium ashes from shell hydrogen burning. The resulting momentum flux is quantified here. And since the cores of AGB stars lack efficient momentum-cancellation mechanisms, they can maint ain equilibrium by exporting their excess momentum flux to the stellar envelope, which disposes of much of it in a low velocity wind. Gravit ational contraction easily accounts for the momentum flux in the solar wind, as well as the flux required to lift mass into the dust formati on zone of every AGB star, whereon radiation pressure continues its ej ection as a low-velocity wind. This mechanism explains the dependence of the AGB mass-loss rate on core mass; its generalization to objects with angular momentum and/or strong magnetic fields suggests a novel e xplanation as to why most planetary nebulae and proto-planetary nebula e exhibit axial symmetry. Quasi-static contraction is inherently biase d to the generation of the maximum possible momentum flux. Its formali sm is, therefore, readily adapted to providing an upper limit to the m omentum flux needed to sustain mass loss when this begins from a semic ontinuous rather than an impulsive process.