The Hubble–Reynolds law models the
surface brightness
In astronomy, surface brightness (SB) quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background. An object's surface brightness depends on ...
of
elliptical galaxies
An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the three main classes of galaxy described by Edwin Hubble in his Hubble sequence and 1936 work ''The Re ...
as
:
Where
is the
surface brightness
In astronomy, surface brightness (SB) quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background. An object's surface brightness depends on ...
at radius
,
is the central brightness, and
is the radius at which the surface brightness is diminished by a factor of 1/4. It is asymptotically similar to the
De Vaucouleurs' law which is a special case of the
Sersic profile for elliptical galaxies.
The law is named for the astronomers
Edwin Hubble
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology.
Hubble proved that many objects previously ...
and
John Henry Reynolds. It was first formulated by Reynolds in 1913 from his observations of galaxies (then still known as nebulae). It was later re-derived by Hubble in 1930
specifically in observations of elliptical galaxies.
References
Astrophysics
Equations of astronomy
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