  A detailed analysis is presented of the dominant ionised knot in the halo of
the planetary nebula NGC 6543. Observations were made at high spectral and
spatial resolution of the [OIII] 5007 line using the Manchester echelle
spectrometer combined with the 2.1-m San Pedro Martir Telescope. A 20-element
multislit was stepped across the field to give almost complete spatial coverage
of the knot and surrounding halo. The spectra reveal, for the first time, gas
flows around the kinematically inert knot. The gas flows are found to have
velocities comparable to the sound speed as gas is photo-evaporated off an
ionised surface. No evidence is found of fast wind interaction with the knot
and we find it likely that the fast wind is still contained in a
pressure-driven bubble in the core of the nebula. This rules out the
possibility of the knot having its origin in instabilities at the interface of
the fast and AGB winds. We suggest that the knot is embedded in the slowly
expanding Red Giant wind and that its surfaces are being continually
photoionised by the central star.

Astrophysics