Published online by Cambridge University Press: 26 May 2016
Outflows in young stellar objects are powered by accretion, and ∼ 0.1 of the accreted material is lost in the outflow. Observational evidence is analyzed in the context of models for the origin of the wind. Winds in FU Ori objects are clear examples of disk winds. In Classical T Tauri stars, there is evidence for the existence of a wide angle wind at scales < 100 AU, which supports the X-wind model prediction that narrow jets are the result of density/temperature enhancement towards the axis of the system. However, recent HST observations of the DG Tau jet indicate that the opening angle of the wind is more confined than predicted by the X-wind model, in better agreement with disk wind theories.