Photon Bubbles in Young Massive Stars
  Spectroscopic studies indicate that gas in the photospheres of young O stars moves at speeds up to the sound speed. We show, using two-dimensional radiation MHD calculations and results from a local linear analysis, that the motions may be due to photon bubble instability if young O stars have magnetic fields. 
N. J. Turner, H. W. Yorke, A. Socrates and O. M. Blaes