case western reserve university



The Chemical Enrichment of Omega Centauri

John E.Norris (Mount Stromlo & Siding Spring Observatories, The Australian National University)

Omega Cen, the most massive of the Galaxy's globular clusters, is chemically inhomogeneous, and presents us with the opportunity of investigating, from the study of individual stars, how an isolated system chemically enriches itself. It contains (at least) three populations with relatively distinct abundances, kinematics, and (possibly) ages. Recent studies show that the main sequence is double, defying explanation. I shall argue that large differences in the abundance of helium (Y) between the populations, of order 0.10-0.15, provide a sufficient, if not necessary, explanation.