The Age of the Universe with Globular Clusters: Reducing Systematic Uncertainties

Understand

The dominant systematic uncertainty in the age determination of galactic globular clusters is the depth of the convection envelope of the stars.

• This parameter is partially degenerate with metallicity which is in turn degenerate with age.
• However, if the metal content, distance and extinction are known, the position and morphology of the red giant branch in a color-magnitude diagram are mostly sensitive to the value of the depth of the convective envelope.
• Therefore, using external, precise metallicity determinations this degeneracy and thus the systematic error in age, can be reduced.