Oxygen burning process
Encyclopedia
The oxygen-burning process is a set of nuclear fusion
reactions that take place in massive star
s that have used up the lighter elements in their cores. It occurs at temperatures around 1.5×109 K
/ 130 keV
and densities of 1010 kg/m3.
The principal reactions are:
|- style="height:2em;"
| ||+ || ||→ || ||+ || ||+ ||9.594 MeV
|- style="height:2em;"
| || || ||→ || ||+ || ||+ ||7.678 MeV
|- style="height:2em;"
| || || ||→ || ||+ || ||+ ||1.500 MeV
|- style="height:2em;"
| || || ||→ || ||+ ||2 ||+ ||0.381 MeV
|- style="height:2em;"
| || || ||→ || ||+ || ||- ||2.409 MeV
|- style="height:2em;"
|colspan=99|Alternatively:
|- style="height:2em;"
| || || ||→ || ||+ ||
|- style="height:2em;"
| || || ||→ || ||+ ||2
|}
With the neon-burning process an inert core of O-Mg forms in the centre of the star. As the neon burning turns off, the core contracts and heats up to the ignition point for the oxygen burning. In about six months to one year the star consumes its oxygen, accumulating a new core rich in silicon. This core is inert because it is not hot enough for silicon burning. Once oxygen is exhausted, the core ceases producing fusion energy and contracts. This contraction heats it up to the point that the silicon-burning process ignites. Proceeding outward, there is an oxygen-burning shell, followed by the neon shell, the carbon shell, the helium shell, and the hydrogen shell.
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
reactions that take place in massive star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s that have used up the lighter elements in their cores. It occurs at temperatures around 1.5×109 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
/ 130 keV
Kev
Kev can refer to:*Kev Hawkins, a fictional character.*Kevin, a given name occasionally shortened to "Kev".*Kiloelectronvolt, a unit of energy who symbol is "KeV".* Krefelder Eislauf-VereinKEV can refer to:...
and densities of 1010 kg/m3.
The principal reactions are:
- {| border="0"
|- style="height:2em;"
| ||+ || ||→ || ||+ || ||+ ||9.594 MeV
|- style="height:2em;"
| || || ||→ || ||+ || ||+ ||7.678 MeV
|- style="height:2em;"
| || || ||→ || ||+ || ||+ ||1.500 MeV
|- style="height:2em;"
| || || ||→ || ||+ ||2 ||+ ||0.381 MeV
|- style="height:2em;"
| || || ||→ || ||+ || ||- ||2.409 MeV
|- style="height:2em;"
|colspan=99|Alternatively:
|- style="height:2em;"
| || || ||→ || ||+ ||
|- style="height:2em;"
| || || ||→ || ||+ ||2
|}
With the neon-burning process an inert core of O-Mg forms in the centre of the star. As the neon burning turns off, the core contracts and heats up to the ignition point for the oxygen burning. In about six months to one year the star consumes its oxygen, accumulating a new core rich in silicon. This core is inert because it is not hot enough for silicon burning. Once oxygen is exhausted, the core ceases producing fusion energy and contracts. This contraction heats it up to the point that the silicon-burning process ignites. Proceeding outward, there is an oxygen-burning shell, followed by the neon shell, the carbon shell, the helium shell, and the hydrogen shell.