ASTR 1102 Lecture : Lecture34
Document Summary
You just won"t believe how vastly, hugely, mind- bogglingly big it is. douglas adams, the hitchhiker"s guide to the galaxy. Some giant ellipticals much bigger than milky way. Also dwarfs of similar mass to globular cluster. Large and small magellanic clouds - satellites of our own. Also distance to center of galaxy from stellar orbits around central black hole. Orbits of masers (microwave lasers) gas clouds orbiting galaxies. Most ways to get distance work this way. Identify some type of object with known luminosity. Compare brightness to luminosity to get distance. Rr lyrae and cepheid variables chapter 19. Tully-fisher relation for spiral galaxies - chapter 24. Faster rotation more mass more luminous. The problem with a distance ladder: ladders wobble! Measure the distance to a galaxy using cepheids. Measure distance to associated stars with spectroscopic parallax. Measure distance to nearby stars using annual parallax. If nearby distances are shaky, whole structure wobbles! We cannot measure their distance, even with supernovae.
