Top: colour-magnitude diagram. Absolute M_g magnitude versus (g − z) colours for the UCD (light blue), the GCs in FCC 47 (blue circles, Jordán et al. 2015), and NSCs in the Virgo cluster (orange triangles, Côté et al. 2006) and in the Fornax cluster (purple triangles, Turner et al. 2012). All magnitudes are in the Vega system. Typical colour errors are shown with the symbols at the top. The uncertainty of the UCD’s colour is roughly the extent of its symbol. Bottom: effective radii for GCs, NSCs, and the UCD. Typical uncertainties given at the left-hand side. There are no uncertainties given for the Virgo NSCs; however, we assume that they are comparable to the Fornax NSC uncertainties.