Q: The Sun has (roughly) absolute magnitude V = 5.
     Where does it fall in this diagram?

           The Sun falls in the middle of the
           diagram -- it is a star of
           ordinary power.


     How many solar luminosities do stars at
     the top of the diagram produce?

           Absolute magnitude M = -4 
           corresponds to about 4,000
           solar luminosities.

              L(star)        0.4*( M(sun) - M(star) )
            ----------  =  10
              L(sun)
                             0.4*(  5  -  [-4] )
                        =  10                    

                             0.4*(9)  
                        =  10           =  4,000




     How many solar luminosities do stars at
     the bottom of the diagram produce?

           Absolute magnitude M = +12
           correponds to about 0.004 
           solar luminosities:

              L(star)        0.4*( M(sun) - M(star) )
            ----------  =  10
              L(sun)
                             0.4*(  5  -  12 )
                        =  10                    

                             0.4*(-7)  
                        =  10           =  0.0016  =  1/630