AST 10G Lecture Notes - Lecture 10: Inverse-Square Law, Elliptical Galaxy, Edwin Hubble
Document Summary
Prove milk way is gas, star clusters, etc. How did he do it: based work on henrietta leavitt, period luminosity (lum. ) Relation of stars ( not all stars have period lum. ) Figure out (inverse square law) how bright it would have to be. Variable could figure out how far away, determine inside or outside mw. Galaxy"s age, distance & universe age related. Light takes time to travel, so farther away obj. older it is, Take bulge out of spiral that would be an elliptical galaxy. Stars of all ages, many gas clouds. Bulge & halo, old stars few gas clouds. Almost all gas and dust in disk of spiral little (not any )in halo. Bulge and halo can be redder and not as lum. Disk uniform circular motion, not attach to anything, bob up and down. Halo obj. have sponge, highly elliptical orbits. Barred spiral galaxy: has bar of stars across the bulge.