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redshift-magnitude relation

(Magnitude-redshift relation)
(how apparent magnitude depends on redshift)

The redshift-magnitude relation (or magnitude-redshift relation) is a function of redshift (or distance) that yields (effectively) the distance modulus associated with that redshift: the difference between apparent magnitude and absolute magnitude. This was of great interest when the expansion of the universe was first being proposed.

It is also of current interest: like the redshift-angular size relation, it is straight-forward given some simplifying approximations: in this case, constant. However, at cosmological distances, various models as well as observation reveal it is not so simple, and observation can be used to select and tweak models.