Astrophysics (index)

Reddening

(Interstellar Reddening)
(red appearance of astronomical objects because blue light is attenuated by dust)

Reddening is the phenomena of blue light from a star being absorbed and scattered by Cosmic Dust, because the cross-section of dust is often close to that of blue light. An abnormally red appearance of an object in space is evidence of dust on the line of sight. Where there is reddening, there is likely to be Extinction of dimmer objects.

A measure of Reddening is Color Excess (EB-V, a particular Color Index), defined as:

EB-V = AB-AV
   where
 AV = V - V0
   and
 AB = B - B0

and

  • B and V are the observed Intensities in the B and V Passbands.
  • B0 and V0 are those that would be observed if there were no reddening.

The Ratio of Total to Selective Visual Extinction (RV) can be used to characterize dust in galaxies:

      AV
RV = ————
     EB-V

(dust,EMR)
http://en.wikipedia.org/wiki/Extinction_(astronomy)

Referenced by:
Extinction
Malmquist Bias
Rayleigh Scattering
UBV Photometric System

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