Stellar nucleosynthesis#Hydrogen burning

With hydrogen burning nuclear fusion of protons (ie, the most common isotope of atomic nuclei 1H of hydrogen ) to form helium in the interior of stars (or, in the case of Nova, on the surface of a white dwarf ) refers. This reaction is normal in stars during most of their life cycle, the major source of energy right corner shows the main sequence stars derive their energy from the hydrogen burning.

The process of nuclear fusion can take place during hydrogen burning in two ways, in each of which four protons are converted into a helium nucleus 4He in various ways:

  • The relatively direct proton-proton reaction
  • Of heavy elements ( carbon, nitrogen, oxygen) -use Bethe- Weizsäcker - cycle ( CNO cycle )

A proton has a mass of 1.007276 u, a neutron of 1.008665 & So Together, two protons and two neutrons in the unbound state has a mass of 4.031882 u A helium nucleus consisting of two protons and bound neutrons and only has an atomic mass of 4.002602 u; it lacks 0.029280 u, ie about 0.73 % of the mass. That person, the mass defect difference in mass is released during fusion as an energy; per gram entstandenem helium are the 657,461,112,381.746 J (short: 6.5746 · 1011 J). This energy corresponds to the nuclear binding energy of the nucleons ( nucleons ) and is calculated from the Einstein relation E = mc2.

The mass defect in the fusion of hydrogen into helium is the largest of all the fusion reactions, and thus with respect to the energy in the most productive; the next stage of stellar fusion reactions, helium burning sets, per carbon nucleus produced only about a tenth of that free.

The energy generation rate is proportional to the proton - proton cycle to the 6th power of the temperature, the Bethe- Weizsäcker cycle to the 15th power. Consequently causes an increase of the temperature by 5%, an increase of 34% and 108% in the release of energy. When helium burning (27th potency) and carbon burning ( 30th potency) these values ​​are again significantly higher.

See also:

  • Nucleosynthesis
  • Carbon burning
  • Neonbrennen
  • Oxygen burning
  • α - particles