Why will the sun stop shining?

Answer 1

Scientists tell us that about five billion years from now the sun will begin to die, just like stars do. First, the sun will get hotter. Then, it will probably swell up, slowly it will become much, much bigger. As it gets bigger, its color will change from yellow to red. As the sun grows bigger, it will pour out more heat. The earth will become so hot that all the rivers, ponds, lakes and oceans will boil and turn to steam. All of the plants and animals will die. The world will become a ball of bare, burnt rock, surrounded by great clouds of steam.

After about a billion more years the sun will begin to shrink. It will become no bigger than earth. Its color will change from red to white. Slowly during more billions of years, its brightness will fade. It will use the last of its energy-and go out. It will be a dead black ball, a little smaller than earth. As the sun gives off less and less heat, the clouds of steam around the earth will turn back into water and fall as rain. Oceans and lakes will fill up again. As the sun grows cooler, earth will grow cold. The water will freeze. Earth will be a lifeless ball of rock and ice-cold, dark and silent!

Answer 2

The sun will eventually stop shining when it exhausts its nuclear fuel, causing it to undergo gravitational collapse and expand into a red giant. This process is estimated to occur in about 5 billion years, leading to the sun's transformation into a white dwarf.