# Carbon, Oxygen and Silicon Burning

## Carbon Burning

After helium burning is completed at the core and temperature reaches up to $5-8 \times 10^{9} K$ carbon burning starts:

$^{12}C + ^{12}C \rightarrow ^{24}Mg + \gamma$

$^{12}C + ^{12}C \rightarrow ^{23}Na + ^{1}H$

$^{12}C + ^{12}C \rightarrow ^{20}Ne + ^{4}He$

$^{12}C + ^{12}C \rightarrow ^{23}Mg + n$

$^{12}C + ^{12}C \rightarrow ^{16}O + 2 ^{4}He$

## Oxygen Burning

Oxygen is consumed at slightly higher temperatures in the reactions

$^{16}O + ^{16}O \rightarrow ^{32}S + \gamma$

$^{16}O + ^{16}O \rightarrow ^{31}P + ^{1}H$

$^{16}O + ^{16}O \rightarrow ^{28}Si + ^{4}He$

$^{16}O + ^{16}O \rightarrow ^{31}S + n$

$^{16}O + ^{16}O \rightarrow ^{24}Mg + 2 ^{4}He$

## Silicon Burning

After several intermediate steps the burning of silicon produces Nickel and Iron.

$^{28}Si + ^{28}Si \rightarrow ^{56}Ni + \gamma$

$^{56}Ni \rightarrow ^{56}Fe + 2e^{+} 2\nu_e$

When the temperature becomes higher than $10^9 K$, the energy of photon becomes large enough to destroy certain nuclei. Such reactions are called photo dissociation. Elements higher than Fe are produced by the neutron capture in the supernova explosion.