GSI-Kolloquium:"Puzzles of the Astrophysical r-Process: How and where are the heaviest elements formed in Nature?"

The existence and abundances of Europium, Gold, Silver, Platinum, Uranium, Plutonium and many other heavy elements are all pointing towards a process of rapid neutron capture with a reaction path close to the neutron drip-line. While many of the nuclear uncertainties remain (masses far from stability, decay half-lives, beta-delayed processes, fission probabilities and fragment distributions), their present knowledge permits a rough understanding of the required conditions for the working of the process, in order to reproduce the solar abundance pattern attributed to the r-process. Basic open questions remain in determining the astrophysical sites(s) where these conditions could prevail. The question is twofold: (a) scenarios which can reproduce the solar abundance pattern, (b) the time evolution and frequency with which these scenarios are expected to occur during the evolution of galaxies. Candidates are core collapse supernovae, mergers of binary neutron stars, a rare highly magnetized fast rotating fraction of supernovae, accretion disks around black holes... We will present and discuss the present status of observations and theory in determining solutions to this puzzle.