8
  Q:  The radius of the Sun is about R = 6.96 x 10   meters.
      What is the bolometric luminosity of the Sun?

                                   2                            4
           L  =  4 pi (6.96 x 10^8)   *  5.67 x 10^(-8) * (5800)


              =  3.9 x 10^(26) Watts