Projected H₂ column densities in the molecular cloud simulation. A total of 233 protostars, denoted with white crosses have formed in this snapshot from the simulation (t = 1.66 Myr). Most protostars form in clusters along filaments. The red diamond marks the protostar that is studied here during the pre-stellar phase. We centered the pre-stellar core in the figure for clarity, since the box has periodic boundary conditions.