= Fundamental plane
{disambiguate=elliptical galaxies}
{title2=$R_e\propto\sigma^a I_e^b$}
{wiki}
= Fundamental plane of elliptical galaxies
{synonym}
The fundamental plane relates effective radius, stellar <velocity dispersion>, and mean <surface brightness> of <elliptical galaxies>. Homologous <virial equilibrium> with constant <mass-to-light ratio> predicts $R_e\propto\sigma^2/I_e$; empirical exponents differ. The two-variable <Faber-Jackson relation> is a projection, not the entire plane.
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