CAREER: Deciphering the Nuclear Fingerprints of Stellar Explosions

Stars end their lives in large explosions called supernovae. During these explosions new elements are created and dispersed into the galaxies that host the dying stars. The newly created elements provide the seeds for the formation of the next-generation of stars and planets, such as our Solar System. Understanding these explosions, their role in element formation, and their connection to our Solar System is a long-standing goal of nuclear astrophysics. The supernovae events also leave behind compact objects such as neutron stars—the densest matter in the Universe. The gravitational pull of these dense neutron stars can suck in material from nearby companion stars. This material undergoes nuclear reactions on the surface of the neutron stars releasing energy as powerful bursts of X-rays. Studying these bursts provides insight into the neutron star interiors. Computer models of nuclear reactions in supernovae show that just a few key elements, if observed, are sufficient to probe these extreme stellar environments, whereas models for nuclear burning on the surface of neutron star show that few reactions are key to understanding the shape of bursts observed using space-based telescopes. This project will measure some of the critical nuclear reactions in the laboratory to shed light on the production and destruction of elements, and energy generation under extreme stellar conditions, helping validate the models and reducing their uncertainty. This research will use radioactive beams at the Facility for Rare Isotope Beams, as well as stable beams at the University of Notre Dame, together with advanced detection systems, to provide first ever measurements of several important stellar reactions. Beyond advancing and driving fundamental science, the project will also train graduate and undergraduate students on these experiments producing the next generation of nuclear scientists and strengthening the nation’s scientific workforce. A Physics Olympics program at Mississippi State University will engage high school students—especially from rural districts—with limited access to physics courses, offering hands-on exposure in an out-of-classroom setting. Current physics students preparing to become teachers will help run the program, fostering innovation and collaboration in science and math education. This project will measure reaction cross sections for key astrophysical reactions at accelerator-based nuclear physics laboratories to elucidate the production and destruction of ⁴³K and ¹⁰Be in core-collapse supernovae (CCSNe) and to constrain energy generation from nuclear burning in type-I X-ray bursts on accreting neutron stars. Observation of ⁴³K in CCSNe can probe explosion energies, while ¹⁰Be is critical to understanding conditions at the birth of the Solar System; its excess in meteorites is established, but its origin remains debated. Reactions near the ⁶⁴Ge waiting point—a defining feature of the rapid proton-capture process powering type-I X-ray bursts—govern energy generation and hence shape of X-ray burst light curves. Measurements will be conducted at the Facility for Rare Isotope Beams (FRIB) using short-lived radioactive beams and the Active Target Time Projection Chamber (AT-TPC), and at the Nuclear Science Laboratory at the University of Notre Dame employing direct and indirect techniques with isotopically enriched targets. Experimentally, this work will deliver the first direct (p,α) measurement with the AT-TPC at FRIB, establishing a foundation for future studies of similar reactions. Overall, the results from this research will provide critical nuclear physics input for CCSNe and XRB models. Graduate and undergraduate students will play central roles in the experiments, and, together with the Physics Olympics program for high school students, the project will advance discovery while strengthening nuclear physics and STEM workforce development. This award reflects NSF's statutory mission and has been deemed worth NSF Award ID: 2542390 | Program: 01002930DB NSF RESEARCH & RELATED ACTIVIT,01002627DB NSF RESEARCH & RELATED ACTIVIT,01003031DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Jaspreet Singh Randhawa | Institution: Mississippi State University, MISSISSIPPI STATE, MS | Award Amount: $462,113 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2542390 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2542390.html