NUCLEOSYNTHESIS I:

HYDROGEN "BURNING" (PROTON-PROTON CHAIN)

A star's energy comes from combining light elements into heavier elements by fusion, or "nuclear burning".

In small stars like the sun, hydrogen burning is the

fusion of 4 hydrogen nuclei (protons)

into a helium nucleus (2 protons + 2 neutrons).

Forming helium from hydrogen gives off lots of

energy (a natural hydrogen bomb).

Nucleosynthesis requires very high temperature. The minimum temperature for hydrogen fusion is 5 million degrees.