CNES, ESA and NASA have invested in helioseismic and asteroseismic disciplines for 2 decades with SoHO (1995–2015), COROT (2006–2013), KEPLER (2009–2014), PICARD (2010–2013) and SDO (2010–2015). These missions focus on the stellar internal dynamics and their influence of neighboring planets. Progress along this path requires that the microscopic physics is well under control, but several seismic probes indicate some discrepancies which justify new investigations of the energy transport in radiative zones of the Sun and massive stars, despite strong efforts dedicated to reaction rates, screening, equation of state and opacity coefficients between 1990 and 2000. We describe here how the OPAC consortium tackles the complex problem of photon absorption by matter both theoretically and experimentally, by using high energy laser facilities. These studies might be also useful for other disciplines like fusion for energy and X-ray spectroscopy astronomy.