An international team of researchers has found that most very bright stars have a companion star, and that there is often a mass transfer from one star to the other. This image is an artist’s illustration of this mass transfer.
H. Sana, S. E. de Mink, A. de Koter, N. Langer, C. J. Evans, M. Gieles, E. Gosset, R. G. Izzard, J.-B. Le Bouquin, & F. R. N. Schneider (2012). Binary interaction dominates the evolution of massive stars Science DOI: 10.1126/science.1223344