Figure 3-53 Balmer Lines in the Spectrum of a Star This portion of the spectrum of the star Vega shows six Balmer lines, from Hα at 656.3 nm through Hζ at 388.9 nm. Absorption lines are therefore caused by photons being taken out of the stream of light by electrons, which thereby move into higher-energy allowed orbits. An observer on the right in Figure 3-49 looking at the hot blackbody through the cloud of cooler gas sees dark absorption lines where photons have been absorbed by the cooler gas.