Figure 11-29Spectra of a Metal-Poor and a Metal-Rich Star These spectra compare (a) a metal-poor (Population II) and (b) a metal-rich (Population I) star (the Sun) of the same surface temperature. Numerous spectral lines prominent in the solar spectrum are caused by elements heavier than hydrogen and helium. Note that corresponding lines in the metal-poor star’s spectrum are weak or absent. Both spectra cover a wavelength range that includes two strong hydrogen absorption lines, labeled Hγ (410 nm) and Hδ (434 nm).