a, The mass growth of the super-remnant outer shell for up to 100,000 eruptions (see key). The diagonal dotted line illustrates a power-law extrapolation of the outer-shell mass to further eruptions. The upper and lower solid grey lines indicate the growth of the outer-shell mass for higher and lower ISM densities, respectively. The horizontal dotted line marks the predicted outer-shell mass at the current extent of the super-remnant. b, The evolution of the expansion velocity of the outer shell (black) compared to the mean velocity within the ejecta pile-up region (red). The diagonal dotted lines indicate power-law extrapolations, the horizontal line the initial injection velocity, and the vertical line the predicted current epoch. c, The evolution of the X-ray (0.3–10 keV) luminosity of the super-remnant (black), the hard (1–10 keV; red) and soft (0.3–1 keV; blue) components are shown for information along with the hardness ratio HR (hard/soft; right-hand axis) evolution; for each, the dotted line indicates a power-law extrapolation to later times. The horizontal dotted black line indicates the 3σ upper limit from the XMM-Newton observations.