First off, we are lucky because the sun has a very long time left to live! Scientists estimate that the sun is currently about 4.5 billion (that's 4,500,000,000 years) years old and has about 5 billion years left to burn. That means that the sun is not yet even halfway through its life.

The sun is made out of hydrogen and helium atoms. On Earth, hydrogen and helium are gases; in fact, helium is the gas that is used to inflate birthday balloons that float in the air. However, in the sun, hydrogen and helium are so tightly packed into one region of space that the hydrogen actually starts to act as a fuel that "burns" to turn into additional helium. When this hydrogen "burns" into helium, a tremendous amount of light and heat is released. This is how the sun is able to provide the Earth with light and warmth.

The sun will eventually burn through all of the available hydrogen and will have no more fuel to continue in its current state, just like cars will eventually run out of gasoline if they are not filled up. At this point, the sun will begin to rapidly change. Scientists think that the sun will begin to instead burn the remaining helium as fuel, which will cause the sun to get much larger, perhaps even large enough to capture the Earth.

Check out the following link for an illustrated video that shows what might happen in 5 billion years, after the sun runs out of hydrogen fuel. Can we survive the sun's death