The Sun has an apparent magnitude of m = -26.7.
  It is about 1.5 x 10^(11) meters from the Earth.
  One parsec is about 3.1 x 10^(16) meters.

         Q:  What is the distance to the Sun, in parsecs?

                  d  =  4.84 x 10^(-6) pc



         Q:  What is the absolute magnitude M of the Sun?


                  (m - M)  =  5 log(d)  -  5

                       M   =  m  -  [  5 log(d)  -  5 ]

                           =  -26.7  -  [  -26.6  -  5 ]

                           =  +4.88



         Q:  Is the Sun more or less powerful than Vega?


                  Sun  M   =  +4.88
                  Vega M   =  +0.57

             Clearly, Vega emits more light than the Sun.  In fact,
             the luminosity of Vega is greater than that of the Sun
             by a factor


                   L(Vega)       -0.4 * (0.57 - 4.88)
                   ------  =   10
                   L(Sun)


                           =   53