LARGE PROPER MOTIONS AND EJECTION OF NEW CONDENSATIONS IN THE HH-80-81 THERMAL RADIO JET

The HH 80-81 complex is the largest and most powerful stellar jet syst em of high collimation known. We have obtained second-epoch (1994.3) V LA observations of the HH 80-81 thermal radio jet and compared them wi th previous observations made 4.1 yr before (1990.2). Both sets of obs ervations were made at 3.5 and 6 cm with an angular resolution of simi lar to 0''13. Large proper motions have been detected in the condensat ions along the jet. These proper motions are in the range of 70-160 ma s yr(-1), equivalent to 600-1400 km s(-1) at the distance of 1.7 kpc o f the source. Such large velocities have not been previously measured in the context of jets from young stellar objects, and they give suppo rt to the identification of the powering source of this Herbig-Haro co mplex as a very massive star. Between the two epochs of observation, a n ejection event created two new knots in the jet flow that in 1994.3 appear symmetrically projected at only 500 AU from the central source. The existence of significant clumpiness and symmetry in the jet so cl ose to the star gives support to the notion that disturbances in stell ar jets are produced by the driving source, and not as a result of ins tabilities produced later in the flow.