Ex Luna, Scientia: The Lunar Occultation eXplorer (LOX) and the Future of MeV γ-Ray Astrophysics

The Lunar Occultation eXplorer (LOX) will perform the first systematic population studies of thermonuclear supernova (type-Ia, SNeIa) using their emergent nuclear radiation. LOX will probe the fundamental nuclear processes that govern these "beacons of the Cosmos" by characterizing the temporal and spectral evolution of their emergent gamma-rays throughout pre-, peak, and post-explosion epochs. LOX measurements of the radioactivity left behind in the wake of nuclear burning will reveal characteristic trends via population studies that individual detections cannot, further our understanding of the matter–energy life cycles within galaxies, and provide critical diagnostic evidence for the multiple evolutionary pathways responsible for SNeIa. LOX will directly test the assumption of SNeIa homogeneity by quantifying the diversity of thermonuclear scenarios and progenitors. To achieve these goals LOX performance fills a long-standing astrophysical capability gap at MeV energies, including the scientific priority for space-based time-domain multi-messenger capabilities. The LOX mission implementation approach mitigates the challenges associated with increasingly complex space-based instrumentation. Science goals are achieved with a simple, low-cost, cross-cutting implementation based on the Lunar Occultation Technique (LOT); implementation and operational simplicity are its hallmarks. LOX leverages the benign, well-characterized lunar environment to achieve transformational performance, and employs a single-instrument payload consisting of an array of identical gamma-ray sensor modules that leverage decades of heritage derived from planetary exploration endeavors. LOX is under review as part of NASA's astrophysics MIDEX program, has significant potential for discovery, will further establish the Moon as a platform for science, and once again pry open a new window on the Cosmos.