English: Nickel production versus heliocentric distance: Blue circles show VLT/X-shooter measurements of 3I/ATLAS (this work); the black solid and gray dashed curves are power–law fits to the 3I data only, giving Q(Ni) ∝ r^(−8.43±0.79) (weighted) and Q(Ni) ∝ r^(−9.09±0.79) (unweighted), respectively. Colored symbols compare with Solar–system comets compiled from the literature, grouped by dynamical class as in the legend; green squares mark measurements for 2I/Borisov. The left axis gives log10[Q(Ni)/atoms s−1] and the bottom axis in log-scale the heliocentric distance r_h (au). The right axis shows an approximate equilibrium surface temperature T(r_h) (orange line; scaled to 200 K at r_h = 3 au) to guide the eye (see text for details). Horizontal dashed lines indicate sublimation thresholds for CO, NH3, CO2, and H2O. Other comets references: Guzik & Drahus (2021), Opitom et al. (2021), Hutsemékers et al. (2021) and Manfroid et al. (2021)