According to the Big Bang Theory, when two particles with lot of energy, collapsed and formed a gaseous body with hydrogen. We call it Sun, with 8 bodies in planetary motion in its orbit. When the hydrogen (fuel) will be finished, the sun will start expanding and engulfing the Mercury, Venus and all the 8 planets, becoming a black hole (which is formed at the death of a star).
Sun is a nothing but a body of 90% heydrogen.
But if this fuel will finish, the gravitational pull will decrease. And according to Einstein's prediction, the Sun will engulf all the planets in the solar system.
forming a black hole
Then what is the confusion?
Sare sutte reh jange