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.
