Interstellar Dust and Extinction

The ultraviolet (UV) region of the spectrum has been crucial in providing information on the nature of the material and size distribution of the particles of interstellar dust. Before there were any measurements of the UV properties of interstellar extinction, interstellar particles were believed to be composed primarily of dirty ices. The maximum of the interstellar extinction was believed to be at 0.3 μm, the shortest wavelength then observable. Both of these predictions were quite wrong (as are probably many of our present ideas regarding dust). The first rocket measurement (Stecher, 1965) showed that there is a very strong extinction feature at 0.22 μm. Now we also know the extinction increases dramatically towards the shortest wavelengths which can be reliably measured to date.

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