2004ApJ...603..595F

We have measured the proper motion (PM) and kinematics of the ansae in NGC 7009 using high-dispersion echelle spectra and archive narrowband Hubble Space Telescope images. Assuming that the ansae are moving at equal and opposite velocities from the central star, we obtain a system radial velocity of -53±2 km/s, the eastern ansa approaching and the western ansa receding at v_r=5.3±1 km/s with respect to this value. The PM of the eastern ansa is 28±8 mas/yr, which, with our weighted distance to NGC 7009 of 0.86±0.34 kpc, gives V_exp=114±32 km/s. The electron temperature and density in both ansae were determined to be T_e∼9000±400 K and n_e∼2300±400/cm3. The dynamic age of the ansae is ∼910±260 yr, and the implied PM of the central star is µ_CS=1±0.5 mas/yr. This is in qualitative but not quantitative agreement with previous work.