Interstellar Extinction
  This review describes our current understanding of interstellar extinction.
This differ substantially from the ideas of the 20th century. With infrared
surveys of hundreds of millions of stars over the entire sky, such as 2MASS,
SPITZER-IRAC, and WISE, we have looked at the densest and most rarefied regions
of the interstellar medium at distances of a few kpc from the sun. Observations
at infrared and microwave wavelengths, where the bulk of the interstellar dust
absorbs and radiates, have brought us closer to an understanding of the
distribution of the dust particles on scales of the Galaxy and the Universe. We
are in the midst of a scientific revolution in our understanding of the
interstellar medium and dust. Progress in, and the key results of, this
revolution are still difficult to predict. Nevertheless, (a) a physically
justified model has been developed for the spatial distribution of absorbing
material over the nearest few kiloparsecs, including the Gould belt as a dust
container, which gives an accurate estimate of the extinction for any object
just in terms of its galactic coordinates. It is also clear that (b) the
interstellar medium makes up roughly half the mass of matter in the galactic
vicinity of the solar system (the other half is made up of stars, their
remnants, and dark matter) and (c) the interstellar medium and, especially,
dust, differ substantially in different regions of space, and deep space cannot
be understood by only studying nearby space.
