Average spectra of the blue and red population stars

Average spectra of the blue and red stellar populations in the globular cluster Omega Centauri. Each spectrum represents an average of spectra of 17 individual stars and a total of 204 hours of exposure time with the FLAMES instrument on the Very Large Telescope. The spectral lines of some elements are indicated. Differences between the two spectra are easily noticeable; a detailed analysis shows that the "blue" spectra correspond to a greater content of heavier elements than the "red" spectra. (VLT KUEYEN and FLAMES)