Nucleosynthesis

The chemical elements were formed long before the existence of the earth. The first step of this so-called nucleosynthesis is the fusion of hydrogen to helium:

¹H + ¹H → ²H + β⁺ + ν
²H + ¹H → ³He
³He + ³He → ⁴He + ¹H + ¹H

In heavy stars, this is followed by the formation of carbon, which is crucial for living organisms:

⁴He + ⁴He → ⁸Be
⁸Be + ⁴He → ¹²C

By further fusion with helium, ¹⁶O, ²⁰Ne, ²⁴Mg, ²⁸Si, ³²S, ⁴⁰Ca, and ⁵⁶Fe are formed. Other elements are the result of nuclear reactions with neutrons, protons and deuterium. Elements heavier than iron are formed by neutron activation in a supernova.

Related concepts

• cosmic radiation
• cosmogenic radionuclide
• natural decay chain
• nuclear fission (natural reactor)
• primordial radionuclide