Échelle diagram showing the observed (orange) and modelled (grey) mode frequencies for ℓ = 0 (circles), ℓ = 1 (triangles), and modelled ℓ = 2 (squares). The observed modes are plotted with their 1σ uncertainties in the horizontal direction if these are larger than the symbol used. The straight ridge of the radial modes and the mixed-mode behaviour of the dipolar modes are evident. Note that model modes without an observed counterpart are also plotted.