Accurate Stellar Opacities To Solve Astrophysical Problems

Ohio State University, The, Columbus OH

Investigators

Abstract

In order to carry out any detailed study of nature on large scales, we often require a precise understanding of the microscopic processes that govern our universe. One of these, called opacity, measures the precise way that electromagnetic radiation (light, in all of its forms) interacts with atoms, molecules, and free-floating subatomic particles. Recent results from studies of the Sun's interior indicate that previous calculations of the relative abundance of the elements are off by an uncomfortable amount. The PI and his collaborators are world leaders in the field of laboratory astrophysics. They will improve the accuracy of opacity calculations guided by results from computer models of stellar interiors, by recent experimental physics results, and by including effects that were previously omitted. While it is primarily theoretical, this work has a very broad range of practical applications in and beyond astrophysics. These include nuclear fusion and medical physics. The PI is active in several programs promoting collaborative US-India efforts in STEM education. This project will involve specialized training of a postdoctoral fellow in this multi-disciplinary research. The PI will lead an effort to properly account for bound-free autoionization resonances and calculate mean opacities for a variety of compositions using improved atomic data and a new high-precision version of the Opacity Project codes. Recent helioseismology results, results from the Z-pinch inertial fusion device at Sandia National Laboratory, and re-examination of current opacities all suggest that true opacities are significantly higher than current models. This work could lead to the solution of the "solar abundance problem", and it is all but guaranteed to lead to improvements in fundamental atomic physics, the equation of state appropriate for stellar interiors that incorporates opacities of elements produced in r-process nucleosynthesis, and improved Rosseland and Planck mean opacities. It is a continuation and extension of prior successful work by the PI and his collaborators, guided by recent measurements and by improvements in computational techniques. Results will be made available to the physics, chemistry, and astrophysics communities via electronic databases.