What is the oldest part of our galaxy?
The Globular Clusters found mostly in the halo surrounding the core of any big galaxy are the most ancient structures found within any galaxy, including our own.
Globular Structures are dense collection of roughly spherically distributed stars. All globular clusters appear red in colour, indicating that they have only small stars that are still active. The massive stars that are blue in colour are absent. Since massive/blue stars die fast and the low mass/red stars live very long, presence of only red stars indicate that the Globular Clusters must be really ancient that all the non-red stars dead by now. The age of Globular Clusters in the Milkyway Galaxy has been estimated to be around 12 Billion Years old.
Age Estimates Of Globular Clusters In Milkyway Galaxy :