Dr. Harriet Dinerstein will use several observational techniques to address the question of how stars undergo the transformation from late stage red giants into planetary nebulae and ultimately white dwarfs. This transitory evolutionary episode is a crucial turning point in stellar life histories, yet it is still not well understood. Dr. Dinerstein will investigate and define the properties of the massive residual neutral envelopes around the ionized cores of planetary nebulae. Recent work has demonstrated the presence of these envelopes and illustrated the use of optical and infrared spectroscopy to determine their parameters. Data on the amount and distribution of neutral material are essential to any comprehensive picture of the mass loss and planetary nebula formation process. Dr. Dinerstein will also study evolved bipolar nebulae, which represent the phase immediately preceding the appearance of a recognizable planetary nebula. By combining results of observations at several wavelengths, Dr. Dinerstein will be able to determine the general geometry of these structures and locate the main mass and emission components. The comparison of objects at different stages of development should clarify the evolutionary progression through this transient and transforming stage of stellar evolution.
