Stellar Atmospheres in the Laboratory: A Testbed for Fundamental Atomic Processes

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Most stars---including our Sun---will end their lives as white dwarf stars, which no longer undergo nuclear fusion. Understanding white dwarf stars is an important tool for astronomy because these stars can serve as cosmic clocks that probe the age and history of the universe. This research project will create in the laboratory conditions that are similar to those found on the surfaces of white dwarf stars. A detailed analysis of the light absorbed and emitted by atoms under such conditions will allow astronomers to better understand white dwarf stars. This project will train graduate students in sophisticated laboratory techniques, and it will support science outreach to local high schools.The research team will conduct new laboratory measurements that will provide key benchmarks for atomic line broadening observed in white dwarf stars. They will make these measurements using an experiment that they have built for the Z-machine at Sandia National Laboratories. The experiment is capable of producing hydrogen, helium, and carbon plasmas that are similar to those in white dwarf photospheres. Accurate atomic spectral line parameters measured in these laboratory plasmas would allow astronomers to accurately diagnose plasma conditions at the surfaces of white dwarf stars and test theories of line broadening there. White dwarf stars could then be used to constrain the age and history of the Galactic disk, Galactic halo, and individual stellar clusters, and as astrophysical laboratories in which to study the fundamental physics of crystallization, phase separation, diffusion, and plasmon neutrino emission. This project will train graduate students in the methods and applications of laboratory astrophysics, and it will provide opportunities to undergraduate students from the Freshman Research Initiative program at UT Austin.