Averaged spectrum of the six spectrum presented in this work, normalized at 0.60 μm. The positions of the absorption bands of CH₄ are represented by dotted lines. The features at 0.43, 0.52, and 0.59 μm are artifacts due to small differences between the spectra of the G2 stars used as solar analogs and those of the Sun. The 0.43 μm structure corresponds to the absorption produced by iron and calcium, the 0.52 μm is due to the magnesium triplet, and the 0.59 μm is due to a sodium doublet.