Illustration depicting the impact of the critical accretion rate (Ṁ_crit) on the evolution of a star. The yellow object represents the protostellar seed and the wave pattern depicts the luminosity wave. The contraction towards blue is depicted with blue lines, whereas the expansion towards red is shown in red lines. The white and cloudy rings represent the accretion; this is denser in cases where the accretion rate is higher than Ṁ_crit and fainter when the accretion rate drops below Ṁ_crit. The black background depicts the pre-MS evolution and the grey background at the top marks the core hydrogen burning phase.