telluric line[tə′lu̇r·ik ′līn]
any of the spectral lines formed in the spectrum of celestial bodies as a result of the absorption of light by the molecules of gases in the earth’s atmosphere, such as oxygen, ozone, water vapor, carbon dioxide, methane, and nitrous oxide. Telluric lines or bands in individual regions of the spectrum, such as the infrared and ultraviolet regions, make the earth’s atmosphere almost opaque to the corresponding radiation. Telluric lines in the spectra of celestial bodies are detected either on the basis of their intensification as a body approaches the horizon or on the basis of the absence of the Doppler shift, usually observed in solar or stellar lines. Telluric lines were first detected by D. Brewster in 1832 during observations of the solar spectrum.