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→Modern definition: Add distance must be measured in parsecs
The apparent magnitude of an object depends not only on how much light the object emits, but also on how far away the object is. To compare the instrinsic brightness of objects, the absolute magnitude is often used. It is defined as the magnitude of an object as seen from 10 [[parsec]]s (32.6156 [[light year]]s). The absolute magnitude, ''M'', can be calculated using,<ref>{{cite web|url=https://astronomy.swin.edu.au/cosmos/A/Absolute+Magnitude|title=Absolute Magnitude|accessdate=July 28, 2020|publisher=astronomy.swin.edu.au}}</ref>
The apparent magnitude of an object depends not only on how much light the object emits, but also on how far away the object is. To compare the instrinsic brightness of objects, the absolute magnitude is often used. It is defined as the magnitude of an object as seen from 10 [[parsec]]s (32.6156 [[light year]]s). The absolute magnitude, ''M'', can be calculated using,<ref>{{cite web|url=https://astronomy.swin.edu.au/cosmos/A/Absolute+Magnitude|title=Absolute Magnitude|accessdate=July 28, 2020|publisher=astronomy.swin.edu.au}}</ref>
:<math>M = m - 5 \log_{10} \frac{d}{10}</math>
:<math>M = m - 5 \log_{10} \frac{d}{10}</math>
where ''m'' is the apparent magnitude and ''d'' is the distance to the object from Earth.
where ''m'' is the apparent magnitude and ''d'' is the distance to the object from Earth. ''d'' must be measured in parsecs for this equation to work.
== Examples ==
== Examples ==