• metal-poor stars
• Population II stars
• Population III stars
• stellar evolution
• stellar interiors

Over the years, several metal-deficient stars have been detected and analyzed by numerous surveys. To enable the detailed interpretation of their observational properties, theoretical stellar models simulating their evolution are required. Currently, in the literature, all the renowned and broadly-employed databases of evolutionary models cover intervals in metallicity “Z” from, approximately, 0.00001, i.e. the distinctive lowest value for stars in old globular clusters, to 0.01, typical of the Sun-like and metal-rich structures. The purpose of this research was to compute an extended library of models (i) to examine the features of the most metal-poor stars ever observed, potentially characterized by values of “Z” smaller than 0.00001 and (ii) to verify the theoretical predictions regarding the stellar evolution at exceptionally low metallicities, fascinatingly different compared to that of more metal-rich structures like the Sun. The newly-calculated database, which is the result of the work of this thesis, consists of more than four hundred models spanning wide ranges of masses and metallicities “Z”, particularly for values of “Z” lower than 0.00001.