Multi-color observations of evolved stars in ω centauri

We present multi-color observations of the northern population of omega Cen from the main sequence turnoff to high on the red giant branch. We show that the best information about the metallicity and age of the stars can be gained from combining vby, B - I, and V - I colors (in tile absence of spectroscopy). We confirm our results for the main sequence turnoff stars: there is at least a 3 Gyr age spread, which may be as large as 5-8 Gyr, as suggested by Hughes & Wallerstein (2000) and Hilker & Richtler (2000). The available evidence supports the idea that W Cen was once the core of a dwarf galaxy, captured and partially stripped by the Milky Way.