AST201H1 Chapter Notes - Chapter 20: Elliptical Galaxy, Spiral Galaxy, Irregular Galaxy

• School: UTSG
• Department: Astronomy & Astrophysics
• Course: AST201H1
• Professor: Michael Reid

Document Summary

Chapter 20: galaxies and the foundation of modern cosmology. The lives of galaxies have been pieced together by analyzing pictures of galaxies at various life stages: to find young galaxies, we have to look deep into the universe (far back in time). Cosmology: the study of the overall structure and evolution of the universe. Three major types of galaxies: spiral galaxies look like flat white disks with yellowish bulges at their center. Disks are filled with cool gas/dust, interspersed with hotter ionized gas and usually have spiral arms: elliptical galaxies compared to spiral galaxies they are redder, more rounded, and elongated like a football. Contain very little cool gas/dust, but do contain very hot ionized gas: irregular galaxies appear neither disklike nor rounded. Spiral/irregular galaxies look white because they contain stars of all different colours/ages; elliptical galaxies look redder because old, reddish stars produce most of their light.