Frontiers of Nuclear Astrophysics Original Research Article

The main goals of nuclear astrophysics have been to probe the interiors of stars, stellar explosions, the early moments of cosmic expansion, and the formation and evolution of galaxies and cosmic structure by measurement and application of the relevant nuclear physics. The approach to these goals have generally been from three directions: 1) Careful measurements of the relevant nuclear reactions; 2) Detailed computer models of the relevant astrophysical environments; and 3) Observations of the relevant terrestrial and extra-terrestrial atomic and isotopic abundances. These approaches provide not only insight into the formation and evolution of the elements, but are also pillars upon which a variety of cosmological models as well as models for physics beyond the standard model of particle physics can stand or fall. At present there is a very exciting frontier on all three of these approaches. The development and applications of radioactive-ion-beam and low-background facilities have begun to clarify the input nuclear physics. The development of hydrodynamic stellar-evolution and explosion models in three spatial dimensions, along with detailed radiation and neutrino transport has provided new and unexpected insights into some of the deep mysteries regarding the origin and evolution of the elements. Also, for the first time in history, ground and space-based observations of elemental abundances in stars and gas are being made from the time of the very first stars and cosmic structures to the present. Observation of the cosmic microwave background can now also be used to analyze the development of structure in the universe from before the time of photon decoupling to the present. These observations provide unprecedented views of the history of cosmic evolution. They also provide new questions. In this review we summarize some some of the developments in each of these areas and highlight the exciting frontiers where new breakthroughs are likely to occur.