Elements of Stars

Abstract

Abstract What are stars made of? Less than 200 years ago this basic, simple question was deemed impossible to answer. As Auguste Comte put it in 1835: “On the subject of stars…While we can conceive of the possibility of determining their shapes, their sizes, and their motions, we shall never be able by any means to study their chemical composition or their mineralogical structure.” Today, we have a broad, clear answer to the question: “What are stars made of?” We also understand its far-reaching implications in relation to the evolution of the cosmos. Satellites and many ground-based spectroscopic surveys routinely provide new discoveries on the chemical composition of astronomical objects. In parallel, the nuclear processes that produce the elements inside stars are investigated in increasingly sophisticated nuclear physics experimental facilities across the world. At the same time, supercomputers allow us to calculate detailed models of the evolution of stars and galaxies: how much of which element is produced where? Finally, the presence of tiny amounts of extra-solar material can be found within meteorites, whose analysis is reaching unparalleled precisions with uncertainties down to parts per million. How have we managed to travel from an impossible question to such broad knowledge filled with discoveries?