c program for equilibrium temp
        print*,'Enter Albedo, Tstar, Rstar (Rsun), a(AU):'
         read*,b,t,r,a
         x=(1.0-b)**0.25
         rr=696000.0*r
         d=a*149600000.0
         y=(rr/2.0/d)**0.5
         print*,y
         tp=t*x*y
         print*,'Tp = ',tp
         stop
           end