Secrets from the Stellar Nursery

Alison Sills

January 31, 2011

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Abstract: Globular clusters are some of the simplest objects in the universe. For this reason, they are fundamental test beds to understand star formation and evolution in much more complex systems like galaxies. Globular clusters are spherical clusters of hundreds of thousands of stars, all of which were formed at the same time, in the same place and from the same material. They are old, and have been passively evolving for almost the age of the universe. They are quite beautiful, and also rather boring. — Or so generations of astronomical students have been taught until a few years ago. I will present evidence that these ancient objects have been keeping secrets from us, and that the events in their stellar nurseries were not quite as simple as we had thought. There is increasing evidence that there is more than one stellar generation in globular clusters ‰ÛÒ not just a single ‰ÛÏbaby boom‰Û, but a complex interplay of stellar birth, death, and rebirth. I will then discuss some of the implications of, and problems with, this new scenario.