Final stacked image of centaur 523676 (2013 UL10), taken on 11 December 2015. The image is in the R filter, and is the coadding of three individual frames for a total exposure time of 900 s. Median airmass is 1.35. The image is displayed in log scale to enhance the low-level activity, together with overplotted isophotes. The linear scale of the image is 5.3 × 10⁴ km. North isup and east is to the left. In the lower left corner, the stacked image of inactive centaur 2008 FC76 (together with overplotted isophotes) obtained in the same observing night is reported for comparison (see text).