Astrophysics Seminar

Red Giants to Planetary Nebulae: Studying the Transitional Objects

Professor Bruce Hrivnak
Valparaiso University

Tuesday, March 29, 2005   3:30 pm   NSH 184

 

 

The evolution of stars of intermediate and low mass, such as the Sun, causes them to pass from the main sequence to the red giant and asymptotic giant branch (AGB) phases and then on through the planetary nebula (PN) phase, finally ending as white dwarfs. The most poorly understood phase in this evolution is that between the AGB and PN phases, the proto-planetary nebulae. Stars in this phase are surrounded by an expanding and obscuring circumstellar envelope. In this talk, I will describe how objects in this phase have been identified and observed, what has been learned about their properties, and how these studies have given us greater understanding of the preceding and succeeding phases of stellar evolution. Topics covered will include the chemistry of the star and nebula, the shape of the nebula, and the mass loss rates; these properties have been derived from observations made at visible, infrared, and radio wavelengths.