RSAA Colloquia / Seminars / Feast-of-Facts: Thursday, 09 April 2015, 11:00-12:00; Duffield Lecture Theatre

Albert Zijlstra

"Life in retirement: old stars in old stellar populations"

Sun-like stars end their lives in a phase of catastrophic mass loss. Between 30% and 80% of the mass of the star is lost in an extreme stellar wind. The ejecta are briefly visible as an ionized, expanding planetary nebula surrounding a hot pre-white dwarf star. The mass loss of Sun-like stars is crucial to both stellar and galactic evolution: it is responsible for the mass distribution of white dwarfs, about half the local ISM, most of the carbon in the Universe, much of the dust and half of all elements heavier than iron. But planetary nebulae, the death shrouds of their stars, are also important as tracers of older stellar populations. They are the most luminous phase in the evolution of their host stars, and emit much of their energy in just a few bright emission lines. About 400 planetary nebulae are known in the Galactic bulge. In this talk I will discuss this population. Planetary nebulae present indications for a younger component to the bulge than the accepted age of 10Gyr. For globular clusters, there is a discrepancy between the presence of mass losing stars and the absence of any interstellar medium. The talk will discus how globular clusters rid themselves of the ejecta.