The Fate of the Sun
About 5 billion years from now, the hydrogen near the center of the Sun
will begin to run out and the helium that has collected there will start
to contract. This will increase the rate of hydrogen burning in a shell
around the core. Our star will slowly bloat into a
and destroy the inner planets of our solar system, including the Earth.
As the helium core continues to contract from gravity, it will soon get
dense and hot enough to fuse three helium particles into carbon. At the
same temperature, the carbon can also fuse with another helium to form
oxygen. Since the Sun is not very massive compared to some stars, it will
never get hot enough in the center to create elements much heavier than
carbon and oxygen. These elements will collect in the center of the star.
Later it will shed most of its atmosphere, creating a planetary nebula,
and emerge as a hot white dwarf star.
Nearly 99 percent of all stars in the galaxy will end their lives as white
dwarfs. By studying the stars that have already gone through this process,
we can learn about the fate of our own Sun.
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