Comparison between coma simulations with different activity distributions given υ_init = 0.5 m s⁻¹, and the observed coma in the first image of sequence STP090. The image of the observed coma is the background signal that we subtracted during the preparation for the tracking procedure (see Sect. 2 and Pfeifer et al. 2022). The ellipse indicates the suspected source region. All images are brightness-inverted and had their contrasts improved individually for better reading. Because of this, the absolute intensity levels should not be compared across images, but only relative to other areas of the same image.