The formation of massive stars remains one of the most significant unsolved
problems in astrophysics, with implications for the formation of the
elements and the structure and evolution of galaxies. It is these
stars, with masses greater than 8-10 solar masses, that eventually explode
as supernovae and produce most of the heavy elements in the
universe. These stars dominate the energy injection into the interstellar
medium of galaxies through supernovae, stellar winds, and UV radiation. By
injecting both heavy elements and energy into the surrounding
medium, massive stars shape the evolution of galaxies. Despite the
importance of massive star formation, relatively little is known about them
theoretically as they pose a major theoretical challenge. These stars
begin burning their nuclear fuel and radiating enormous amounts of energy
while still accreting gas. For the most massive stars greater than 100
solar masses, the luminosity can approach the Eddington limit, at which the
radiative acceleration due to Compton scattering is equal to the
acceleration due to gravity. However, the opacity of dust in the accreting
matter can be significantly greater than the Thomson cross section
resulting in acceleration due to radiation pressure that can greatly exceed
that of gravity for all stars above 10 solar masses. This leads to a
fundamental problem: How is it possible to sustain a sufficiently high
mass accretion rate into a protostellar core despite the radiation pressure
on the accreting envelope? I will discuss our recent work on the first 3D
simulations of massive star formation. Using our high resolution 3D
radiation-hydrodynamic adaptive mesh refinement code ORION with a
relativistically correct treatment of the radiation transport, we have
investigated the formation of high mass stars from both smooth and
turbulent initial conditions in the collapsing massive core. I will
discuss our work on identifying 2 new mechanisms that efficiently solve the
problem of the Eddington barrier to high mass star formation; the presence
of 3D Rayleigh Taylor instabilities in radiation driven bubbles present in
the accreting envelope and the presence of protostellar outflows providing
radiation an escape mechanism from the accreting envelope. I will present
the results of 3D simulations, predictions for upcoming EVLA submillimeter
observations and outline future directions.