What is the term used for the phenomenon where interstellar dust dims a star's apparent brightness due to wavelength-dependent scattering?
Answer
Extinction
The interaction between starlight and interstellar dust leads to two related observable effects described by specific terminology. The general dimming of a star's apparent brightness as its light travels through dust clouds is termed extinction. This effect is coupled with reddening, which is the shift of the star's observed color toward the red end of the spectrum. Both extinction and reddening occur because the dust grains scatter shorter, bluer wavelengths of light away from the direct line of sight much more efficiently than longer, redder wavelengths, thereby altering both the star's measured luminosity and its color index.
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