Cosmic rays are sub-atomic particles that reach the earth from outer space. Some cosmic rays are the highest energy particles ever detected by humans, far exceeding the energies produced in the largest particle accelerator experiments. The origin of these ultra-high energy cosmic rays and the distribution of their masses remains a mystery. A science collaboration between Virginia Polytechnic Institute and State University and Pennsylvania State University will carry out a research program designed to further knowledge of the origins of ultra-high energy cosmic rays (UHECR) by establishing detailed connections to massive stars, and to two different, but related types of exploding stars: supernovae and gamma-ray bursts. The research will focus on understanding the distribution of masses of ultra-high energy cosmic rays, which will be used to address long-standing challenges in the quest for unraveling the origins of cosmic rays. The work will benefit from ongoing discoveries of how supernovae explosions are driven, and the development of a new multi-messenger astronomy that combines traditional observations of light with observations of cosmic rays and other particles from space. The research is interdisciplinary, requiring detailed astrophysical numerical models, applications of nuclear physics, and considerations of sub-atomic particle acceleration and interactions. Finally, the project includes an active outreach program aimed at local high schools. The centerpiece is the integration of a smartphone app "Crayfis" that detects UHECR by a network of smartphone CCDs triggering on the particles called muons created by the cosmic-rays. The app will be used as a catalyst to share excitement in astrophysics and discovery and it will leverage the existing Virginia Tech QuarkNet infrastructure to work with high school teachers, thereby reaching out to a large and broad range of students.
A comprehensive numerical study, starting from the origins of nuclei in jets to their pathways to ultra-high energy cosmic rays, will be performed. These studies will deliver predictions for the mass compositions of ultra-high energy cosmic rays and allow quantitative comparisons with ultra-high energy cosmic-ray and multi-messenger observables. The main tasks of the proposal are: (i) to establish detailed predictions for the nuclear mass compositions of engine-driven supernovae and gamma-ray burst jets; (ii) to quantify the modification to such nuclear abundances during jet propagation, cosmic-ray acceleration in dissipation regions, and cosmic-ray propagation in intergalactic space; (iii) to make signal predictions for cosmic ray and multi-messenger observables; and (iv) to perform quantitative comparisons with data. Together, these tasks will deliver a quantitative assessment of engine-driven supernovae and gamma-ray bursts as sources of ultra-high energy cosmic ray nuclei. This project advances the goals of the NSF Windows on the Universe Big Idea.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
