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In: Planetary Science
The sun started out as a large cloud of gas. Over time, gravity pulled that gas into a dense ball. As it did so, it began to heat up. Eventually the heat and pressure was so much that it started forcing hydrogen to fuse together into helium. This releases a lot of energy which counteracts the pull of gravity, so the sun settled into a stable size and shape, with its immense gravity balanced out by the constant release of energy from fusion.
A byproduct of this is all of the light the sun releases that eventually reaches earth.
Eventually, all of the hydrogen in the sun’s core will be converted into helium and the fusion process will stop. When this happens, there will be nothing counteracting gravity and the core will shrink. The hydrogen in a layer around the core will begin fusion causing the sun to expand into a red giant, possibly consuming the Earth in the process. This is estimated to happen in about 5 billion years.
After another billion years, this second layer of hydrogen will have been converted into helium, and this helium core will have built up enough heat and pressure to begin fusing into carbon. And basically a pattern emerges, with the core fusing into a heavier element until all of it is exhausted, then an outer layer around the core doing the same. Each time some of the suns outermost layers will shed, until it has expelled enough gas to create a planetary nebula, leaving a small core known as a white dwarf that will eventually fade until a black dwarf when it loses all of its energy.
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