Reading the book of Globular Clusters with the lens of Stellar Evolution

Reading the book of Globular Clusters with the lens of Stellar Evolution – Globular Cluster studies are essential for a number of active topics in  Astrophysics and Cosmology. Given their old age and their spatial  distribution, these self-gravitating objects provide useful information on the  modes with  which Galaxies assemble and evolve. The presence of  stars of various masses, and in different evolutionary phases, turn Globular Clusters into a living laboratory, where a  number of issues  related to stellar evolution theory can be investigated. No other stellar  aggregate offers the unique opportunity of harbouring contemporary main sequence stars and tiny, compact objects,  at the last stages of their life. The considerable progress made in the domains of high-resolution photometry and multi-object spectroscopy has produced precise data, that raise many challenging issues for the understanding of the formation process of Globular Clusters, and of the structure and evolution of their member stars. In particular, it is now well extablished that most Globular  Clusters harbour multiple stellar generations, a result stimulating a renewed and controversial debate on the modes  with which these  structures formed, and the nature of the possible polluters of the  interstellar medium. Also, the characteristics of the member stars that  can be determined with exquisite details have highlighted the limits of  our understanding of stellar evolution and bring invaluable clues on internal stellar hydrodynamics.

Hence the idea of a meeting on the observational and theoretical aspects  of the structure, formation, and evolution of Globular Clusters, with the  programme centered around the following topical questions:

1) Evolution of observations of Globular  Cluster stars, from the early  Color Magnitude Diagrams, to  current photometry and high-resolution  spectroscopy. Where are we? What should we expect next?

2) Role of Globular Clusters as laboratories for stellar evolution studies:  from the shape of the Main  Sequence, to the morphology of the  Horizontal Branch. What have we learnt about physical processes of stars  from Globular Clusters?  Is the “second-parameter” problem definitively solved? How well can we date Globular Clusters?

3) Compact objects in Globular Clusters, and the delicate interplay  between the physical conditions of the stellar environment and the rate of production of compact objects. Can we now answer  long standing questions, such as which properties of Globular  Clusters affect the presence of millisecond pulsars, or what is the fraction of White Dwarfs locked in binary systems?

4) New challenging scenarios for the formation of Globular  Clusters,  invoked by the discovery of multiple populations. Are there any possibility of discriminating between the various hypotheses? How does the new paradigm impact our understanding of the chemical and dynamical  features of various astrophysical systems from the local to the high redshift universe?

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