Comparison of the projection on the plane of the sky of the outer radius of the jet, y_m (blue), with the position of the brightness temperature peak, y_peak (black), and the border between the optically thin and optically thick parts of the jet, y₁ (red). All quantities are plotted as a function of time from the onset of the radio outburst (July 10, 2016). The black circles indicate our VLA data, the triangle the OLHKP data, and the two squares our ALMA data. We remark that y_peak is measured from Fig. 5 as the separation between the star and the projection of the peak along the jet axis.