Encyclopædia Galactica Rami T. F. Rekola Tuorlan Astronomical Society Tuorla Observatory University of Turku

Distance modulus ([mu] or DM)

A measure of distance for professional astronomers. The distance modulus really is the difference of an object's apparent and absolute magnitudes. The distance in parsecs can be calculated with equation:

DM = m - M = 5 lg (r / 10 pc) + A

where m is the apparent and M the absolute magnitude, r is the distance in parsecs, and A extinction.