Dark absorption features in the solar spectrum, mapped and labelled by Joseph von Fraunhofer. They give reproducible wavelength landmarks for spectroscopy and optical measurements. Solar and terrestrial absorbers contribute different features to a ground-observed solar spectrum.
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Fraunhofer lines are specific dark absorption lines that appear in the spectrum of sunlight and other stars. They were first observed by the German physicist Joseph von Fraunhofer in the early 19th century. These lines are caused by the absorption of light at particular wavelengths by elements and molecules in the Sun's atmosphere and interstellar medium.