dichroic extinction(dÿ-kroh -ik) Extinction by aligned grains of interstellar dust, which causes polarization of starlight. Light with its polarization vector lying along the projected long axis of the grain is absorbed more than light of the orthogonal polarization. This gives rise to a net excess of light polarized perpendicular to the direction of grain alignment. See also interstellar extinction.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006