Predictions of NS cooling according to the minimal cooling paradigm (see Page et al. 2009). The light- and dark-gray lines represent the cooling curves of NSs with light- and heavy-element envelopes, respectively. The curves for intermediate-element envelopes are between them. Each envelope group includes 100 curves corresponding to four choices of ³P₂ gaps, and five choices of neutron ¹S₀ and proton ¹S₀ gaps. The pink belt indicates the luminosity range of an NS in an age range of 5–6 kyr.