The sun has been shining for approximately 4.6 billion years, but like all stars, it will eventually come to an end. Although the sun's demise is not imminent, its death is a natural part of the life cycle of stars, and scientists have been studying it for decades. iStock When the sun runs out of fuel, it will begin to cool and contract. The sun's outer layers will expand, causing it to become a red giant. During this phase, the sun will grow to be much larger than its current size, swallowing up the inner planets, including Earth. This event is predicted to occur in about 5 billion years from now, based on current estimates. Eventually, the sun will run out of fuel completely, and it will collapse in on itself. This will cause a massive explosion, known as a supernova, which will release a vast amount of energy into the universe. The sun's core will be compressed to form a white dwarf, a small, extremely dense star that will slowly cool over bill...