Astronomy HyperText Book: Interstellar Medium

Документ взят из кэша поисковой машины. Адрес оригинального документа : http://zebu.uoregon.edu/textbook/ism.html
Дата изменения: Sat Jan 24 02:25:24 1998
Дата индексирования: Mon Oct 1 22:06:30 2012
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Much Still Under Development

The Interstellar Medium (ISM) is the stuff between the stars. Most of this stuff consists of gas and dust . The gas content of the ISM continually decreases with time as new generations of stars form from the collapse of giant molecular clouds. The collapse and fragementation of these clouds give rise to the formation of stellar clusters . Since the mass function of star formation strongly favors the formation of low mass stars, then each new star formation locks up available ISM gas into a reservoir of unevolving low mass stars. Click here for a schematic representation of the form of the mass function.
The dust particles are sufficiently small that they scatter short wavelength light more efficiently than long wavelength light. In fact, blue photons are scattered about 10 times more efficiently than red photons. Basic Principle of Photon Scattering
No Scattering: Photon Source and Detector
For optical photons, scattering goes as wavelength to the -4 power. In the case of blue photons compared to red photons, this means that blue photons are about 10 times more likely to get scattered than red photons. This is shown in the next animation.
Watch the blue photons scatter away from the detector
Here we see that only the red photon survives the scattering network to reach the detector
Interstellar dust make stars appear redder than they really are

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