Surface density around an accreting, migrating planet at different times. At the beginning, the planet has a low mass (5 M_⊕) and does not perturb the surface density appreciably. As the planet grows, it changes the surface density in its vicinity both by accreting gas and by pushing disc material away through tidal interaction. After 1000 orbits, the planet has migrated to ≈4.2 au, reached a mass of 1 and opened a gap in the disc. The planet’s initial location (5.2 au) is indicated with a thin black vertical line. This simulation is described in more detail in Sect. 4.1.