What is solar luminosity?

Amount of energy scattered by sun per second in all directions is called as solar luminosity of the sun. Its symbol is L_s.

Let’s suppose that there is a hollow sphere and sun is present at its centre. Take the radius r of the hollow sphere =1A.U. i.e. 1.496 x 10¹¹m.
Surface area of sphere = 4 r². So, the inner surface of the hollow sphere will receive all the radiations of the sun. As we have supposed that sun is present at its center. The luminous intensity will be given by:

L_s = 4 r²S.

Or
L_s = 4 x 3.142 x (1.496 x 10¹¹) ² x 1388

= 3.9 x 10²⁶watt.