Interstellar extinction: Electromagnetic waves from distant objects (stars, galaxies) areInterstellar diffuse matter(Gas or dust) partially absorbs and scatters, resulting in the attenuation of luminosity.
The same reason can lead toInterstellar reddeningPhenomenon: due toInterstellar matterThe degree of absorption and scattering of starlight at different wavelengths is different. The long wave scattering is small, and the short wave scattering is large. Therefore, the received starlight is redder than the starlight without scattering and absorption.[1]
In 1930,SwitzerlandastronomerTrumplerIt is the first time to prove the existence of interstellar extinction.Interstellar varietyDiffuse nebula、Planetary nebula、Dust globuleAnd so on are extinction substances.For lowSilver weftThe phenomenon of interstellar reddening is more serious for.This is similar to the reason why the sun is red at sunset.The observation of distant stars must deduct the influence of interstellar reddening in order to get the correct distribution information of stars.
Known absorption characteristics include 2175ÅPeak (Stardust DIB), 3.1μmWater ice, etc.
The V-belt extinction in the UBV system near the solar system generally adopts 0.7 - 1.0 mag/kpc, that is, for every 1 kpc away, the star brightness will increase by one magnitude (2.5 times weaker).
Extinction curve
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Extinction A at wavelength λλDefined as:
, where FλIs the observed radiation flow, FλzeroIs the measured radiation flow when the light is not extinguished.Noting that the latter is difficult to measure directly, a series of different methods have been derived.
Extinction curve (A)λ(Or take logarithm)~1/λ curve.[2]
