Dynamical effects of stellar winds and shocked gas on interstellar clouds

Stellar winds are a ubiquitous feature of nearly all stars. Their energy input may affect the dynamics of interstellar gas on scales from 1015 to 1021 cm. New observations suggest that powerful winds are also present during the pre-main sequence phase of massive stars. This review summarizes recent observations and theories of winds and high velocity gas, with special emphasis on inhomogeneities in O-star winds, shocked molecular clouds, H2O masers, and Herbig-Haro objects. The difficulties of current models for these phenomena are discussed, and several consequences of protostellar ejection of planet-sized condensations are explored. (Auth.)