### 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.

(*astrophysics,cosmology,measure*)
**Further reading:**

http://en.wikipedia.org/wiki/Redshift

https://ned.ipac.caltech.edu/level5/Sept01/Sandage/Sand4.html

https://ui.adsabs.harvard.edu/abs/2014JCAP...12..042H/abstract

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