The effect of clumping on predictions of the mass-loss rate of early-type stars

Massive stars in our galaxy lose a significant amount of mass through radiation-driven stellar winds. This mass loss influences the course of their evolution, determines the type of supernova explosion they will experience, as well as the nature of the compact object they leave behind. We discuss different mechanisms through which early-type massive stars lose mass. There is mounting evidence pointing to a discrepancy in the mass loss rates predicted from theory and those derived in empirical studies. Part of this evidence is reviewed. The discrepancy may be caused by inhomogeneities that arise in the stellar wind due to the intrinsically instable nature of the wind driving mechanism, that so far have not been treated in predictions of mass loss. We take first steps towards a consistent treatment of clumping in mass loss predictions.