HST observations of Uranus’ Lyα emissions used in this study. Panels A and B: high S/N exposures average images (in native HST detector frame and smoothed for display purposes only). S denotes the position of Uranus’ geometric south pole in all 1998 exposures, while N represents that of north pole in the exposure taken on 31 August 2021. Finally, 0 R_U represents the centre of Uranus in the STIS images. Panel C: average radial Lyα profiles.