Harvard University Department of Astronomy

The Cosmological Constant Age Basic Idea: Age of the universe depends on lambda and H0. Universe cannot be younger than objects in it. Systems of interest: Globular clusters What they are: clusters of stars What one measures about them: main sequence turnoff (how many stars are left) Usefulness as age indicator Observations Method and criticisms: trick is to model stars and to get their distances correctly Current Results Systems of interest: White Dwarfs What they are: burnt out stars What one measures about them: fainter = older Usefulness as age indicator Observations Method and criticisms: fainter = hard to find Current Results Other tests: Low metallicity stars What they are: stars which formed a long time ago What one measures about them: amount of various elements including radioactive Thorium Usefulness as age indicator Observations Method: advantages and criticisms Current Results Future plans and hopes with this method Other cosmological tests these can be used for Some References Home Syllabus References Lecture References Useful Links Contact Info