Astrophysics (Index)About

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 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

The ratio of total to selective visual extinction (RV) can be used to characterize dust in galaxies:

      AV
RV = ————
     EB-V

Differential reddening refers to a varying amount of reddening for different portions of a group of stars with basically similar reddening, such as a stellar cluster. If a cluster's reddening is consistent, a "straight" color-magnitude diagram reveals information on the stars, e.g., their age groupings, that is blurred away if there is differential reddening, and techniques have been developed to work around this.


(dust,EMR,stars)
Further reading:
https://en.wikipedia.org/wiki/Extinction_(astronomy)#Interstellar_reddening
http://astronomy.swin.edu.au/cosmos/I/Interstellar+Reddening

Referenced by pages:
absolute magnitude (M)
color index
dark matter
distance modulus (μ)
extinction
intergalactic dust
Kapteyn universe
luminosity distance (dL)
Malmquist bias
Mie scattering
Rayleigh scattering
spectral energy distribution (SED)
spectroscopic parallax
STARSMOG
UBV photometric system

Index