Hubble-Reynolds Law
Encyclopedia
The Hubble-Reynolds Law models the surface brightness
of elliptical galaxies
as
Where
is the surface brightness
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 Sérsic Law for elliptical galaxies.
Surface brightness
The overall brightness of an extended astronomical object such as a galaxy, star cluster, or nebula, can be measured by its total magnitude, integrated magnitude or integrated visual magnitude; a related concept is surface brightness, which specifies the brightness of a standard-sized piece of an...
of elliptical galaxies
Elliptical galaxy
An elliptical galaxy is a galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless brightness profile. They range in shape from nearly spherical to highly flat and in size from hundreds of millions to over one trillion stars...
as
Where
is the surface brightnessSurface brightness
The overall brightness of an extended astronomical object such as a galaxy, star cluster, or nebula, can be measured by its total magnitude, integrated magnitude or integrated visual magnitude; a related concept is surface brightness, which specifies the brightness of a standard-sized piece of an...
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 Sérsic Law for elliptical galaxies.