de Vaucouleurs Law
Many elliptical galaxies have a projected luminosity distribution that follows a de Vaucouleurs (or R^1/4) law:
or, on a magnitude scale,
So, a plot of surface brightness in magnitudes versus radius to the quarter power for such a galaxy will appear as a straight line.
Note that this law is a purely empirical fit with no physical basis.
However, any theory of elliptical galaxy formation must reproduce it.
) 14th June 1995 (last updated June 14th 1995)