OUTFLOW FROM PROTOSTARS 



Protostar 



Proto Planetary Disc 



Molecular Cloud 



Collapsing Envelope 



Jet and Associated 

 Herbig-Harbo Objects 



Molecular Cloud Shock 

 (-15 Mms) 



Figure 3-5. Schematic of a stellar wind-driven shock model of a protostar. 



with oppositely directed velocity fields. Some even show evidence for precession 

 (i.e., the gradual rotation of the axis of outflow with time). In a few cases the 

 HH objects can be traced back, essentially to the ejecting stars, in the form of 

 well-collimatcd "jets." In two cases, a radio jet continues to the star from the 

 nearest HH object. Stellar binarity is reasonably well established for two systems 

 and may be important in others, but the mass ratios of these binaries are totally 

 unknown. The inferred (projected) orbital planes of these binaries are orthog- 

 onal to the flow direction from the system. Airborne far-infrared measurements 

 for a number of HH-exciting stars have resolved the emitting regions at 50 and 

 100 jum orthogonal to the flow direction. But even the smallest far-infrared 

 beam sizes obtainable with the present airborne observatories are unable to 

 resolve these regions in the flow direction. The emitting regions have radii of 

 about 10 3 to 10 4 AU and presumably they represent the flattened, collapsing 



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