PHYS 183 Chapter Notes - Chapter 20: Inverse-Square Law, Cosmological Principle, Before Present
Document Summary
20: galaxies and the foundation of modern cosmology. Galaxies come in many sizes, colours & shapes. Most galaxies located relatively nearby are the around the same age as the milky. Way to study young galaxies must look far away (farther we look, farther back in time it is) Cosmology: the study of the overall structure and evolution of the universe. Spiral galaxies: look like flat white disks with yellowish bulges at centres; disks filled with cool gas & dust with interspersed hot ionized gas; milky way. Elliptical galaxies: redder, more rounded, often elongated like a football; contain very little cool gas & dust but very hot, ionized gas irregular galaxies: neither disk-like nor rounded colours in galaxies differ from different stars in them. & elliptical since tend to have less cool gas than normal spirals but more than elliptical. Elliptical galaxies common in clusters (hundreds-thousands of galaxies) Measurements tell us distances, size & age of observable universe.
