It is usually accepted to consider an apsidal motion in binary stars as a direct confirmation that a substance inside stars is not uniformly distributed. It is shown in this paper that the apsidal motion in binary systems observation data is in a good agreement with an existence of uniform plasma cores inside stars if they consist of hydrogen-deuterium-helium mixture.
@article{arxiv.astro-ph/0110255,
title = {The apsidal motion in close binary stars},
author = {B. V. Vasiliev},
journal= {arXiv preprint arXiv:astro-ph/0110255},
year = {2007}
}