An Etymological Dictionary of Astronomy and Astrophysics

An empirical power-law correlation between the luminosity (L) and the velocity dispersion of stars (σ) in the center of a elliptical galaxies.
The original relation can be expressed mathematically as: L ∝ σ^γ, where the index γ is observed to be approximately equal to 4, but depends on the range of galaxy luminosities that is fitted. → Tully-Fisher relation.

See also: After the astronomers Sandra M. Faber and Robert Earl Jackson, who
first noted this relation in 1976 (ApJ 204, 668); → relation.