The origin of heavy elements: r-process nucleosynthesis in neutron star mergers

The Big Bang produced mostly hydrogen and helium. Nuclear fusion in stars produces elements up to iron and supernovae create iron peak elements (A ~ 56). Most of the remaining heavier elements are produced by neutron capture. In this talk, I will discuss the origin of the elements with an emphasis on heavy elements. I will give an overview of the slow and rapid neutron capture processes (s- and r-process) and I will briefly address the open question of the r-process site. I will then describe recent nucleosynthesis results I have obtained with my reaction network code SkyNet. Those results focus on neutron star mergers, which seem to be the most promising site for the r-process. Finally, if time permits, I will discuss the potential optical counterparts of r-process nucleosynthesis events, called kilonovae.