BIDIRECTIONAL RELATIVISTIC JETS OF THE RADIO GALAXY 1946- CONSTRAINTSON THE HUBBLE CONSTANT(708 )

We present measurements of bidirectional motions in the jets of the ra dio galaxy 1946+708 at z = 0.101. This is a compact symmetric object w ith striking S-symmetry. Sensitive 15 GHz observations reveal a compac t component at the center of symmetry with a strongly inverted spectru m, which we identify as the core. From five 4.9 GHz observations sprea d over 4 yr we have determined the velocities of four compact jet comp onents. If simple kinematic models can be applied, then the inclinatio n of the source and the bulk jet velocity can be directly determined f or any assumed value of the Hubble constant. Conversely, the measureme nts already place constraints on the Hubble constant, and we show how further observations of 1946+708 can yield an increasingly accurate de termination of H-0.