Observational Evidence for Galactic Spiral Structure

Abstract

Does our Galaxy possess spiral structure and, if so, can this structure be traced observationally with some degree of confidence? This is the major question to which I shall address myself tonight. Following my talk, Professor Lin will speak about the theoretical aspects of spiral structure. I shall be very brief in my references to spiral structure in galaxies outside our own and leave it largely to Professor Lin to speak about observations on other spiral galaxies and their relevance for possible theoretical interpretations.A year ago, my good and distinguished friend Professor B. A. Vorontsov-Velyaminov chided me in his address at the Basel Symposium for having been too eager to accept the fact that observation suggests that our Galaxy really possesses spiral structure. I hope to show in my Discourse that for our Galaxy we have indeed evidence for the presence of an underlying structure of spiral features.