Final answer:
Most stars in the Milky Way's halo are 12 to 13 billion years old, providing evidence for the Galaxy's early formation period and serving as a fossil record for astronomical study.
Step-by-step explanation:
The age of most stars in the Milky Way's halo is estimated to be quite old. Astronomical research indicates that these stars are 12 to 13 billion years old. This is deduced from the age of stars found in globular clusters as well as those dispersed throughout the halo of our Galaxy which suggests that the Milky Way began forming roughly 13 billion years ago.
The halo stars, being among the oldest components, provide insights into the early history of the Galaxy and remain as a sort of "fossil record" of the Milky Way's formation.
The Protogalactic Cloud and the Monolithic Collapse Model describe the early stages of the Milky Way's formation. Based on the distribution of halo stars, it's assumed that the protogalactic cloud from which the Milky Way formed was spherical. The stars formed from this cloud have been orbiting in the halo ever since, without being affected by the later collapse that formed the Galaxy's disk.
While the central bulge of the Milky Way contains some stars that are more than 10 billion years old, most of the stars in the Milky Way's halo are at least 13 billion years old. This discrepancy in age between bulge and halo stars is of significant interest to astronomers studying the evolution and formation of our Galaxy.