Probing nuclear reactions in stars

The ability to accurately determine the rate of this H-¹⁷O fusion reaction provides nuclear physicists with another key puzzle piece, alongside direct observations of oxygen elemental and isotopic abundances in stellar atmospheres and in primitive meteorites, to zero in on complete and accurate models of stars. This information helps establish strong constraints for stellar models, probe complex mixing of matter deep inside stars, and reveal the origin of ¹⁷O in our Galaxy.

To improve our understanding of the Galaxy, scientists study in the laboratory the nuclear reactions that power stars. Such experiments are extremely difficult because the nuclear reactions occur at a tiny rate and their signal is overwhelmed by the environmental background radiation. A breakthrough occurred at the Laboratory for Experimental Nuclear Astrophysics (LENA) at the Triangle Universities Nuclear Laboratory, where a combination of a very high hydrogen beam current (2.0 mA on target) and strong detector background reduction (by two orders of magnitude) enabled researchers to probe the H-¹⁷O fusion reaction directly at stellar energies. The results impact our understanding of the origin of ¹⁷O in the Galaxy and of how matter is transported and mixed in stars from the interior to the surface.