Transmittance maps of WASP-121b at 0.6 μm for the five orbital phase angles whose spectra are shown in Fig. 15. The orbital phase angle is ϕ = − 15° for ingress and ϕ = 15° for egress. For visual reasons, the planet atmosphere has been enlarged with respect to its radius, and the early and late transmittance maps are slightly shifted. Only half the planet covers the star at ingress and egress.