The Sun gives off energy, and that energy can be found deep in it's core, the Sun is busily converting mass into energy. According to Einstein equation of mass and energy equivalence, from his very famous equation E = mc².
Given: Energy E = 3.6 X 10²⁶ J
Speed of light c = 3.00 x 10⁸ m/s
Required: Mass m loss by the sun each second
Formula: E = mc² derive for mass m
m = E/c²
m = 3.6 x 10²⁶ Kg.m²/s² or J/(3.00 X 10⁸ m/s)²
m = 4 x 10⁹ Kg or the Sun is loosing
m = 4 million tons of mass each second