Exploring the Stellar Graveyard of the Milky Way

98% of all stars will end their lives as white dwarfs. In old stellar populations, such

as globular clusters and stellar halos, the bulk of the progenitor stellar mass function

above the present day turnoff is therefore now populated on the white dwarf cooling sequence.

These remnants have remarkable properties and can be studied in exquisite detail to reveal

their temperatures, gravities, and masses. In this talk, I will describe unprecedented

HST imaging and Keck spectroscopic observations of these stars in old stellar populations.

This work has led to the first global constraints on the mapping between initial stellar

mass and final mass, and therefore has broad applications for understanding stellar evolution

theory, mass loss, and chemical enrichment of the interstellar medium. Additionally, through

a new technique, I will describe how we can invert the process of stellar evolution to establish

a relation between the remnant mass in an old stellar population and the parent age. By applying

this technique to nearby Milky Way halo stars, we measure the age of the inner halo of the Milky Way to be 11.4 +/- 0.7 Gyr.