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Stars and the Universe

Stars  -  Life Cycle  -  Birth  -  Fusion (continued).

Fusion releases large amounts of energy.
Where does the energy come from?

If you add up the mass of the nuclei before and
after fusion, you find that some mass has gone missing.
The process of fusion destroys a little bit of mass.
This little bit of mass turns into a large amount of energy.

The process of fusion (nuclei joining together) continues
in stars eventually making bigger and bigger nuclei.
Helium nuclei can fuse to make carbon and further
fusion can lead to the formation of nitrogen and oxygen.
These larger nuclei are called "heavier elements".
Older stars start making the heavier elements up to iron (Fe)
which has a mass number of 56.
All of the elements with larger mass numbers than iron
(cobalt to uranium) are only made in a supernova explosion.

Uranium and other heavy elements are present in the core
of the Sun and the rocks of the planets in our solar system.
This is evidence that the Sun and the planets
formed from the remains of a previous supernova.

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