The blue Main Sequence ( bMS ) of \omega Cen implies a ratio of helium to metal enrichment \Delta Y / \Delta Z \approx 70 , which is a major enigma .
We show that rotating models of low metallicity stars , which account for the anomalous abundance ratios of extremely metal poor stars , are also useful for understanding the very high \Delta Y / \Delta Z ratio in \omega Cen .
Models of massive stars with moderate initial rotation velocities produce stellar winds with large He– and N–excesses , but without the large C– ( and O– ) excesses made by very fast rotation , in agreement with the observed chemical abundance ratios in \omega Cen .

It is still uncertain whether the abundance peculiarities of \omega Cen result from the fact that the high velocity contributions of supernovae escaped the globular cluster , usually considered as a tidally stripped core of a dwarf galaxy .
Another possibility is a general dominance of wind ejecta at very low Z , due to the formation of black holes .
Some abundance and isotopic ratios like Mg / Al , Na / Mg , Ne / N , ^ { 12 } C / ^ { 13 } C , ^ { 16 } O / ^ { 18 } O and ^ { 17 } O / ^ { 18 } O may allow us to further discriminate between these scenarios and between the AGB and massive star contributions .

tars : Omega Centauri – Helium – stars : evolution