Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Absorption Spectroscopy

  • Steven B. CharnleyEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_9-3


Absorption Spectroscopy Interstellar Medium Solar Atmosphere Solar Spectrum Molecular Absorption 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


In absorption spectroscopy, the spectral features of interest appear in absorption with respect to a background continuous spectrum. In the interstellar medium, the background continuum may be supplied by a radiation source, such as a star, located behind the region of interest. The absorbing material may be either in the gas or the solid phase (e.g., interstellar dust or ices). Solid state features are much broader than atomic or molecular absorptions and are consequently more difficult to assign to a specific carrier. Much of the solar (Fraunhofer) spectrum is seen in absorption, as the outer cooler layers of the solar atmosphere absorb radiation from the deeper photosphere. Spectral lines in planetary atmospheres are typically seen in absorption, against the continuous thermal spectrum from the planetary or satellite surface.


The first person to notice a number of dark features in the solar spectrum was the English chemist William Wollaston in 1802. This absorption spectrum was first systematically investigated by Joseph von Fraunhofer, starting in 1814, and the spectral features are now known as Fraunhofer lines.

See Also

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© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Solar System Exploration Division, Code 691, Astrochemistry LaboratoryNASA Goddard Space Flight Center, Code 699GreenbeltUSA