DUST IN THE NEUTRAL GLOBULES OF THE HELIX NEBULA, NGC-7293

Images of the ionized knots and spokes within the helical structure of the Helix nebula have been obtained with subarcsecond resolution in the light of the H-alpha + [N II], [O III] 5007 angstrom and [O II] 3727 angstrom emission lines. The [OIII] image reveals the knots and their tails in absorption. The globules and tails must be dusty and are seen against the diffuse, central [O III]-emitting volume of the Helix nebula. The curved heads of these neutral knots are radiatively ionized by the light of the central star to produce spatially resolved, bow-shaped H-alpha + [N II] and [O II]-emitting structures displaced (measured for the most prominent globule) by 1.65 arcsec (3.1 x 10(15) cm) towards the central star from the peak of the absorption. Assuming a standard interstellar dust/gas ratio and reddening laws, we find that the total mass in one globule is greater-than-or-equal-to 1.0 x 10(-5) M. and the mean gas density N(H) is 6.2 x 10(5) cm-3. Considerations on the nature and survival of the globules and their tails are also discussed.