AST201H5 Lecture Notes - Lecture 7: Active Galactic Nucleus, Quasar, Cosmological Principle
Document Summary
Assume that the mw location is not special. Assume that every other galaxy observes what we observe. Hubble law does not mean that galaxies are moving through space away from each other. Expanding universe means that space is growing. - if the universe is expanding, it had to be smaller in the past. Distance = betwen mw and another galaxie. Speed of separation (assumed constant) = redshift of the other galaxy. 1 galaxy -> an age for the universe. Many galaxies -> a good average age. Recall the hubble law: velocity = ho x d. Distance/velocity = 1/ho = time -= age of the universe. We find galaxies back as far as we can see -> galaxies formed at the beginning of the universe. Always have been s, e and i galaxies. Unlike stars, overtime galaxies collide and merge. Young (= very distant) galaxies have centres that are brighter than whole galaxies.
