ASTR 3 Lecture 23: Notes 23: Galaxies and Dark Matter
Document Summary
Unlike spiral galaxies, their shape in the sky isn"t necessarily their real shapes. No galactic disk at all, in increasing stellar density in center, brighter. Little gas or dust anywhere, thus no young stars. The old stars (low mass, because massive ones don"t live long), mostly red. S0: elliptical galaxy, also called lenticular galaxies, have bulges and disks but no spiral arms, no gas or dust. Not intrinsically irregular, but disturbed by another galaxy. Kepler"s third law: p, semi-major axis and mass. The period cannot always be measured, but we can measure the velocity through the doppler effect. Large mass / small distance: large gravitational force, large velocity. From the center of the galaxy: r. velocity: how fast it"s travelling from its orbit. Solid-body rotation: velocity increases as the distance from the center increases. Close to the sun: fast due to high gravitational force. velocity increases as the distance from the center decreases.
