Extended red emission (ERE) is a dust luminescence process which has recently been attributed to photoluminescence by hydrogenated amorphous carbon. If its presence can be demonstrated on a galactic scale and, in particular, in dust forming environments, ERE must be considered direct observational evidence for the presence and physical structure of an important dust compound, that is, amorphous carbon. Planetary nebulae are recognized as one of the major sources of new interstellar dust, and there is some evidence that ERE is very likely to be present in many of these objects. Planetary nebulae also exhibit evidence for substantial dust grain processing. Dr. Witt will carry out observational studies of the optical continuum in the wavelength range of 3200 to 10,000 Angstroms of 24 planetary nebulae. His aim is to investigate the strength and the spectrum of ERE as a function of the carbon to oxygen ratio in these nebulae and as a function of the size distribution of the dust grains present.
