Structure and stability of primordial stars

Abstract

For decades large-scale cosmic structures have been modeled as the gravitational ampli cation of small-densityperturbations of the cosmological recombination epoch of the Big Bang. In astrophysics, cosmological nucleosynthesisis considered responsible for the production of the pristine gas, which should be found in the rst-generation stars inthe form of hydrogen and helium as the main constituents. In the later type of second-generation stars, hydrogen isconverted into helium by the CN-cycle reactions, in which heavier elements are produced. These elements are believedto enrich the intergalactic medium by possible star bursts at the last stages of evolution.Stability criteria in the stellar evolutionary models pointed out that rst-generation stars should be massive andlive long enough for the nucleosynthesis of the natural elements, heavier than hydrogen and helium. Initially, they wereexpected to be very faint and blue to be observed spectroscopically. Nowadays, more and more metal-de cient starobservations, made possible by the new era of space telescopes, are interpreted as the discovery of a primordial footprintof the initially pure gas. These new data are combined with the astrophysical models to review the predictability, mass,and chemical composition with regard to stability and existence of the rst-generation stars.