An Etymological Dictionary of Astronomy and Astrophysics
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The dimming of light during its travel in the → interstellar medium due to absorption by → intervening → dust grains. Since shorter wavelengths are particularly affected, the spectrum of the light is increasingly dominated by the long wavelength end of the spectrum. As a result, the light is "reddened" as it travels through space. Robert J. Trumpler (1886-1956), a Swiss-American astronomer, was the first to produce a definite evidence of the existence of → interstellar extinction and to estimate its magnitude (1930).

→ interstellar; → reddening.

A graph showing the relation between → interstellar absorption (in magnitudes) and wavelength.

→ interstellar; → reddening; → curve.