De Vaucouleurs's law

In astrophysics, de Vaucouleurs' law describes the surface luminosity profile of an elliptical galaxy as a function of radius R

$\ln I(R)=\ln I_{0}-kR^{1/4}$

By defining R_e as the radius of the isophote containing half the luminosity (i.e., the radius of the inner disk contributing half the brightness of the galaxy), de Vaucouleur's law may be written as

$\ln I(R)=\ln I_{e}+7.67\left[1-\left({\frac {R}{R_{e}}}\right)^{1/4}\right]$

where I_e is the surface luminosity at R_e.

External links

• Eric Weisstein's World of Astronomy entry