# How do the fusion reactions in the sun compare to the fusion occurring in larger stars and supernovas?

Dec 13, 2016

Different fusion reactions occur in small stars, large stars and supernovae.

#### Explanation:

In a smaller star such as the Sun the main process of fusion from Hydrogen to Helium is the proton-proton chain reaction. This is where two protons combine under the strong nuclear force to form a diproton.

${\text{_1^1H + ""_1^1H -> }}_{2}^{2} H e + \gamma$

The Helium 2 or diproton is very unstable and usually breaks down into two protons. Occasionally transforms into deuterium by the weak nuclear force.

${\text{_2^2He -> }}_{1}^{2} H + {e}^{+} + {\nu}_{e}$

Then a proton is added to form Helium 3.

${\text{_1^2H + ""_1^1H -> }}_{2}^{3} H e + \gamma$

There are several reactions which depend on the temperature of the star which lead to the most stable ""_2^4He.

Larger stars use the CNO fusion reactions. This creates Helium from Hydrogen by a fusion process converting Carbon to Nitrogen to Oxygen and back to carbon. There are several reactions.

${\text{_6^12C + ""_1^1H -> }}_{7}^{13} N + \gamma$
${\text{_7^13N -> }}_{6}^{13} C + {e}^{+} + {\nu}_{e}$
${\text{_6^13C + ""_1^1H -> }}_{7}^{14} N + \gamma$
${\text{_7^14N + ""_1^1H -> }}_{8}^{15} O + \gamma$
${\text{_8^15O -> }}_{7}^{15} N + {e}^{+} + {\nu}_{e}$
${\text{_7^15N + ""_1^1H -> ""_6^12C + }}_{2}^{4} H e$

In the case of supernova explosions, vast quantities of free neutrons are released when the core collapses. A process called neutron capture creates elements heavier than Iron. Many elements heavier athan Iron and up to Plutonium are created in this way.