TAP COLLOQUIUM: Stellar Astrophysics as a Physics Laboratory

ABSTRACT: Stellar modeling incorporates a diverse set of tools from theoretical physics to understand the evolution of stars and stellar populations. Our best stellar models are constantly challenged by new observations, from peculiar classes of individual stars to new features in stellar populations from large surveys like Gaia and soon LSST. These confrontations with new data offer exciting opportunities to learn about the physical processes operating in stellar interiors. In this talk, I will focus on a few recent examples of the physics that we are learning about from extreme and unusual white dwarfs. The precision astrometry of the Gaia space mission has introduced a fascinating variety of puzzles in understanding the physics at play in white dwarfs, from their peaceful cooling over long timescales to violent explosions as thermonuclear supernovae. I will explore some of the most exciting recent physics problems introduced by the last decade of white dwarf observations, including: (1) how the structure of cooling white dwarf populations reveals dramatic and unexpected properties of phase transitions in dense multi-component plasma mixtures, and (2) how the structure of extreme hypervelocity runaway stars relates to the physics of thermonuclear supernova explosions.