Mass-averaged nuclear energy generation (left panels), bolometric luminosity (middle panels) and luminosity observed at a viewing 20^∘ (right panels). The upper panels show the heating and luminosities generated by the decay of ⁵⁶Ni and ⁵⁶Co (solid lines), the contribution of all remaining isotopes (dashed lines), and the total (thin lines). The dotted black line in the upper left panel indicates a heating rate proportional to t^−1.3. The lower panels show the relative contribution of ⁵⁶Ni and ⁵⁶Co in each of the above panels.