Astronomy - Colloquia

Star-forming environments vary by orders of magnitude in density, pressure, metallicity, and other properties, yet the initial mass function (IMF) of the stars they produce remains stubbornly unchanged. Explaining the origin and universality of the IMF is one of the oldest problems in theoretical astrophysics, but in the last few years theoretical advances in understanding how gas fragments, together with algorithmic advances that have allowed simulations to include improved physics such as radiative transfer, have produced significant progress. I describe these advances, and lay out the beginnings of a theoretical model capable of explaining the IMF. This model suggests that the IMF is nearly but not perfectly universal, and the subtle variations that it admits provide avenues for future observational tests.