This theoretical study is concerned with the determination of the far-wing photoabsorption spectra of Mg(3s² – 3s3p) while the magnesium atoms are evolving in a helium gas. The quantum-mechanical calculations are carried out by using the most recent and reliable ab initio MgHe potentials and transition dipole moments of Mella et al., Reho et al., Hinde, and Paul-Kwiek and Czuchaj. They showed the appearance, beyond the temperature T=2000 K, of a satellite in the blue wing arising mostly from the free-free ¹Σ⁺ − ¹Σ⁺ transitions.