sciencetalk

Volgens mij hebben een proton en een neutron dezelfde massa, namelijk 1u.

Terug naar de vraag. Een massa afname is helemaal niet zo vreemd omdat er ook (veel) energie vrijkomt (E = Mc²). Tevens zijn er ook isotopen van waterstof (Deuterium en Tritium) Die wel neutronen in de kern hebben.

The Sun and other stars are powered by the fusion of hydrogen or helium.

Solar neutrinos are a different type of radiation emitted by the nuclear reactions in stars. Electrons and positrons (anti-electrons) are delocalised because the matter in stars is a plasma. These leptons may also be considered a form of solar radiation, but they do not travel far from the solar body. Fusion begins with the combination of four hydrogen-1 nuclei to create two hydrogen-2 nuclei. As a result, two positrons (positive electrons) and two neutrinos are released. These two hydrogen-2 nuclei, together with another two hydrogen-1 nuclei, form two helium-3 nuclei and release gamma radiation. These two unstable isotopes of helium fuse to form helium-4 and two particles of hydrogen-1.

The whole process can be summed up by saying that four protons undergo fusion to produce a helium nucleus and energy. The energy radiated away in the form of gamma radiation, as well as the positrons and neutrinos, is solar radiation. The hydrogen-1 nuclei are not radiation, by its strict definition, as they are usually used again as an input in the fusion chain-reaction.

Also note that energy is conserved, so by calculating the mass of the four protons, and the mass of the helium nucleus, and subtracting you can calculate the mass of energy (energy and mass are interchangeable) emitted in gamma and positron radiation. The equation E = mc2 can be used to convert between mass and energy in joules. Since these values are very small, it is useful to convert joules into electron volts. An eV (electron volt) is equal to 1.6 × 10-19 joules, but in most cases the energy released in reactions is measured in MeV or mega-electron volts, or larger quantities.