How Protostellar Outflows Help Massive Stars Form
  We consider the effects of an outflow on radiation escaping from the infalling envelope around a massive protostar. Using numerical radiative transfer calculations, we show that outflows with properties comparable to those observed around massive stars lead to significant anisotropy in the stellar radiation field, which greatly reduces the radiation pressure experienced by gas in the infalling envelope. This means that radiation pressure is a much less significant barrier to massive star formation than has previously been thought. 
Mark R. Krumholz (1), Christopher F. McKee (1 and 2), and Richard I.   Klein (2 and 3) ((1) UC Berkeley Physics Department, ...