Title: The Synthesis of Organic Compounds in the Circumstellar Environment

Sun Kwok
University of Calgary, Canada


Abstract:

Recent observations by the Infrared Space Observatory (ISO) have found
evidence of rapid synthesis of complex organic molecules in the late
stages of stellar evolution.  The chemical synthesis begins with the
formation of acetylene, the first building block of benzene, in carbon
stars. In a following proto-planetary nebulae stage, emission features
corresponding to stretching and bending modes of aliphatic compounds are
detected.  When these objects evolve to become planetary nebulae, aromatic
C-H and C-C stretching and bending modes become strong. These results show
that complex carbonaceous compounds can be produced in a circumstellar
environment over a period of only a few thousand years.

In this talk, we will briefly describe the origin and evolution of
planetary nebulae, the discovery of proto-planetary nebulae, the discovery
of the unidentified 21-micron emission feature, and a possible scenario of
chemical evolution of organic material in the circumstellar environment.