The expulsion of their envelopes by red supergiants is a crucial moment in an intermediate-mass star's history. The expelled envelope glows from the light of the hot remant core of the star and is called a "planetary nebula." The remnant eventually cools to become a white dwarf star enriched in intermediate elements such as C,N,O,Ne. In this three-year renewal award, the Principal Investigator (PI) will study both the structure of the nebulae from recent images in the light of various molecules and the evolutionary paths of the proto- white dwarfs defined by different masses and chemical abundances of the initial star. It is expected that this group will add to their already substantial contributions to our understanding of this critical juncture in stellar evolution.
