Stellar and nuclear astrophysics

In the early Universe, approximately three minutes after the Big Bang, when the cosmic plasma was still very dense and had temperatures of the order of few billion Kelvin, nucleosynthesis started by pulling together protons and neutrons to form the nuclei of light chemical elements like deuterium, helium, and lithium. All other chemical elements have been created later by cosmic-ray spallation processes, thermonuclear fusion reactions and other processes within stars. This means that the carbon, oxygen, nitrogen, silicon, iron, and all other chemical elements that we measure in the atmosphere of the Sun and other stars in the Milky Way and detect among the cosmic rays that hit Earth’s upper atmosphere originated from several generations of stars, which polluted the interstellar medium of galaxies through stellar winds and supernova explosions. The building blocks of life on Earth are the ashes of nuclear fusion reactions that happened within other stars in the past, which then disseminated across the Galaxy with time.

At the E.A. Milne Centre we investigate how chemical elements are created in stars, with the aim to constrain different possible nucleosynthesis scenarios and progenitors starting from astronomical observations. To this end, we bridge together several disciplines ranging from modelling nuclear reaction networks taking place within stars to the analysis of meteoritic data and studying how the chemical composition of the stars and interstellar medium of galaxies changes as a function of time, developing cutting-edge theoretical models and cosmological hydrodynamical simulations, which are then compared to the latest available observational data. Our aim is to answer one of the fundamental questions in astrophysics but also of science in general: what’s the origin of the chemical elements that we observe in the Universe?