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Stars and the Universe

Stars  -  Life Cycle  -  Red Giant.

What is a Red Giant?

When a main sequence star has used up its hydrogen, it will
expand to form a red giant. A large star forms a red super giant.

The helium nuclei in a red giant fuse to make carbon.
The red giant may be many times bigger than the main
sequence star that it came from. It appears red
because the surface of the expanded star has cooled.

We would expect the star to contract as it cooled down.
It expands for complicated reasons which you don't need to
know for GCSE. You just need to know that it is bigger
and cooler than the main sequence star from which it came.

Depending on the size of the red giant, it may then become
a white dwarf (small stars) or a supernova (big stars).

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