Figure 11-16 RIVUXG Spectra of a Metal-Poor Star and a Metal-rich Star The abundance of metals (elements heavier than hydrogen and helium) in a star can be inferred from its spectrum. These spectra compare (a) a metal-poor, Population II star and (b) a metal-rich, Population I star (the Sun) of the same surface temperature. We described the hydrogen absorption lines Hγ (wavelength 434 nm) and Hδ (wavelength 410 nm) in Section 2-4.