telluric lines

telluric lines

(tĕ-loor -ik) Absorption lines seen in the spectrum of a celestial object but due to components, such as water vapor, oxygen, or carbon dioxide, in the Earth's atmosphere. Telluric lines can be distinguished because they are generally narrower than solar or stellar lines, etc. In addition, they vary in strength with the position of the source and are strongest when the source is on the horizon.