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Theneon-burning process is a set ofnuclear fusion reactions that take place inevolved massivestars with at least 8Solar masses. Neon burning requires high temperatures anddensities (around 1.2 billionK or 100keV and 4 billion kg/m3).
At such high temperaturesphotodisintegration becomes a significant effect, so some neonnuclei decompose, absorbing 4.73 MeV and releasingalpha particles.[1] This free helium nucleus can then fuse with neon to produce magnesium, releasing 9.316 MeV.[2]
Alternatively:
where the neutron consumed in the first step is regenerated in the second.
A secondary reaction causes helium to fuse with magnesium to produce silicon:[2]
Contraction of the core leads to an increase of temperature, allowing neon to fuse directly as follows:[2]
Neon burning takes place aftercarbon burning has consumed allcarbon in the core and built up a newoxygen–neon–sodium–magnesium core. The core ceases producing fusion energy and contracts. This contraction increases density and temperature up to the ignition point of neon burning. The increased temperature around the core allows carbon to burn in a shell, and there will be shells burning helium andhydrogen outside.
During neon burning, oxygen and magnesium accumulate in the central core while neon is consumed. After a few years the star consumes all its neon and the core ceases producing fusion energy and contracts. Again, gravitational pressure takes over and compresses the central core, increasing its density and temperature until theoxygen-burning process can start.
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