DEPARTMENT OF PHYSICS DISSERTATION DEFENSE: Joshua Tong

Title:  Dark Matter in Celestial Bodies

Abstract: Dark matter makes up most of the matter in the Universe, but its fundamental nature remains unknown. New discovery strategies are therefore needed. In this talk, I will present three approaches to probing dark matter with stars and planets. First, I will discuss how dark matter captured inside celestial bodies can annihilate and produce observable signals, and I will identify which objects are optimal across different dark matter masses, annihilation channels, and mediator regimes, including a new search using the Galactic Center stellar population. Second, I will present a new dark matter signal: ultraviolet airglow from giant-planet atmospheres, produced when dark matter annihilation products excite molecular hydrogen. Using Voyager and New Horizons flyby data from Jupiter, Saturn, Uranus, and Neptune, I will show that this effect already sets leading constraints on dark matter interactions. Finally, I will discuss how multiple planetary observables, including ultraviolet airglow, ionospheric measurements, and internal heat flow, provide complementary probes of dark matter scattering in Earth and Solar System planets. Together, these results establish stars and planets as powerful, complementary laboratories for discovering or constraining dark matter.