In Astronomy, one calls module of distance the difference between the Magnitude connect $m$ and the absolute Magnitude $M$ of a star. It generally notes with the Greek letter $\backslash \; mu$. The module of distance is in a certain manner another unit (specific to astronomy) of measurement of the distance, like the Année-lumière and the Parsec. The module of distance is written simply:

$\backslash \; driven\; =\; m\; -\; M\; =\; 5\; \backslash \; log\; (D)\; -\; 5$

where $D$ is the distance in parsec. The module of distance is generally used for extragalactic objects (i.e. for stars or galaxies apart from our own galaxy), like the Petit and the Grand Cloud of Magellan, or the Galaxie S of the local Groupe.

For example, the Large Cloud of Magellan has a module of distance equal to 18.5. The Galaxie of Andromède has a module of distance from 24.4 and the galaxy NGC 4548 in the Virgo Cluster has a module equal to 31.0. In the case of the Large Cloud of Magellan, that means that famous the Supernova SN 1987A, with a maximum magnitude connects of 2.8, has an absolute magnitude of 2.8-18.5=-15.7, which is relatively weak for a supernova of this type.

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