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

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

Document Summary

Because nearby galaxies tend to be similar in age to the milky way, we know that most galaxies formed when the universe was much younger and have aged along with the universe itself. The lives of galaxies are therefore intimately connected with the evolution of the universe, making the study of galaxies a part of cosmology the study of the overall structure and evolution of the universe. Spiral galaxies: look like flat white disks with yellowish bulges at their centers. The disks are filled with cool gas and dust, interspersed with hotter ionized gas, and usually displays beautiful spiral arms. Compared with spiral galaxies, elliptical galaxies contain very little cool gas and dust, though they often contain very hot, ionized gas. Irregular galaxies appear neither disklike nor rounded. Spiral and irregular galaxies look white because they contain stars of all different colors and ages, while elliptical galaxies look redder because old, reddish stars produce most of their light.