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The Cosmological Constant
Age


Basic Idea: Age of the universe depends on lambda and H0. Universe cannot be younger than objects in it.

  1. 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

  2. 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

  3. 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


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Comments or Questions? Contact jcohn@astron.berkeley.edu