Model of the spatial extent of SiO emission around V838 Mon. The mesh structures show two regions with different velocity fields and density (or intensity) power laws which reproduce channel maps and position–velocity diagrams of the SiO line. The outer shell contains a characteristic void which the model attempts to reproduce. The “front” view (top left) corresponds to that of the terrestrial observer. The model origin corresponds to the centroid position of component M. An animation is provided online.