Astrophysics

Stellar Signatures

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Science  22 Mar 2002:
Vol. 295, Issue 5563, pp. 2179-2181
DOI: 10.1126/science.295.5563.2179e

Omega Centauri (ω Cen) is one of the most massive and luminous globular clusters in the Milky Way Galaxy. Clusters are among the earliest structures that formed in the universe, and the evolutionary origin of their stars has been a long-standing puzzle.

Pancino et al. examined the relative abundances of Ca, Si, Fe, and Cu in six red giant stars in ω Cen with high-resolution spectra obtained from the ESO Very Large Telescope. They find that three of the red giants belong to the metal-rich branch and are enriched in Cu relative to Fe. This is a signature of ejecta from type Ia supernovae (SNe Ia) and suggests that the cluster retained SNe Ia- derived elements and subsequently incorporated them into these metal-rich stars. Furthermore, the relatively young age of the three red giants (about one billion years) implies that enrichment occurred rapidly or that they represent stars from a smaller and younger cluster that merged with the older cluster early in the life of the Milky Way. — LR

Astrophys. J., in press (astro-ph/0202397).

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