The [absolute magnitude](https://learn2.open.ac.uk/mod/glossary/showentry.php?eid=1147130&displayformat=dictionary "S284 Glossary: absolute magnitude") of a star is (arbitrarily) the value of its apparent magnitude if it were placed at a standard distance away of pc (in the absence of any interstellar matter to absorb its light). It is represented by the symbol and is given by: #### M = m - 5 $log_{10}$ (d/pc)+5 The absolute magnitude of a star therefore gives a measure of its intrinsic brightness, or the amount of energy it _emits_ per unit of time. [[../Chapters/Part 2 Photometry measuring brightness]] [[Docent/S284 Astronomy]]