Faber–Jackson relation
The Faber–Jackson relation provided the first empirical power-law relation between the luminosity 
  
    
      
        L
      
    
    {\displaystyle L}
  
 and the central stellar velocity dispersion 
  
    
      
        σ
      
    
    {\displaystyle \sigma }
  
 of elliptical galaxy, and was presented by the astronomers Sandra M. Faber and Robert Earl Jackson in 1976. Their relation can be expressed mathematically as:

  
    
      
        L
        ∝
        
          σ
          
            γ
          
        
      
    
    {\displaystyle L\propto \sigma ^{\gamma }}
  

with the index 
  
    
      
        γ
      
    
    {\displaystyle \gamma }
  
 approximately equal to 4. In 1962, Rudolph Minkowski had discovered and wrote that a "correlation between velocity dispersion and [luminosity] exists, but it is poor" and that "it seems important to extend the observations to more objects, especially at low and medium absolute magnitudes". This was important because the value of 
  
    
      
        γ
      
    
    {\displaystyle \gamma }
  
 depends on the range of galaxy luminosities that is fitted, with a value of 2 for low-luminosity elliptical galaxies discovered by a team led by Roger Davies, and a value of 5 reported by Paul L. Schechter for luminous elliptical galaxies. The Faber–Jackson relation is understood as a projection of the fundamental plane of elliptical galaxies.