On plasma radiative properties in stellar conditions

TL;DR

This paper reviews recent advances in understanding stellar plasma properties, emphasizing the importance of laboratory measurements of opacity and ionization to improve stellar models and interpret seismic data.

Contribution

It highlights the need for laboratory experiments to measure absorption coefficients and ionization states under astrophysical conditions relevant to stellar evolution.

Findings

Helioseismology has verified key physics in solar models.

Laboratory measurements can improve opacity data for stellar conditions.

Experimental challenges in replicating stellar plasma conditions are discussed.

Abstract

The knowledge of stellar evolution is evolving quickly thanks to an increased number of opportunities to scrutinize the stellar internal plasma properties by stellar seismology and by 1D and 3D simulations. These new tools help us to introduce the internal dynamical phenomena in stellar modeling. A proper inclusion of these processes supposes a real confidence in the microscopic physics used, partly checked by solar or stellar acoustic modes. In the present paper we first recall which fundamental physics has been recently verified by helioseismology. Then we recall that opacity is an important ingredient of the secular evolution of stars and we point out why it is necessary to measure absorption coefficients and degrees of ionization in the laboratory for some well identified astrophysical conditions. We examine two specific experimental conditions which are accessible to large laser facilities and are suitable to solve some interesting questions of the stellar community: are the solar internal radiative interactions properly estimated and what is the proper role of the opacity in the excitation of the non radial modes in the envelop of the $\beta$ Cephei and the Be stars ? At the end of the paper we point out the difficulties of the experimental approach that we need to overcome.