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distance modulus(moj -ŭ-lŭs) The difference between the apparent magnitude, m , and the absolute magnitude, M , of a star and therefore a measure of distance (see magnitude):
where d is the distance in parsecs. Distance modulus is used to determine the distances of stars and stellar clusters. It is corrected for interstellar extinction by an additional term (see magnitude).
in astronomy, the difference between the apparent (m) and absolute (M) magnitudes of a celestial body. This quantity is used to describe distances to stars and stellar systems. Whereas M depends only on the intrinsic luminosity of a star, m depends also on the distance r (in parsecs) to the star, that is, m – M = 5 log r — 5.