Galaxy morphology

Abstract

Hidden in the bewildering details of galaxy morphology are clues to how galaxies formed and have evolved over a Hubble time. This article reviews the phenomenology of galaxy morphology and classification using an extensive set of illustrations to delineate as many types as possible and to show how different types connect to various physical processes and characteristics. The old classification systems are refined, and new types introduced, as the explosion in available morphological data has modified our views on the structure and evolution of galaxies.