helium came from primordial nucleosynthesis in the early universe.
helium came from primordial nucleosynthesis in the early universe.
where did helium come from the early universe?
primordial nucleosynthesis
Na
Na
the unusual stability of the helium-4 nucleus is also important cosmologically: it explains the fact that in the first few minutes after the big bang, as the "soup" of free protons and neutrons which had initially been created in about 6:1 ratio cooled to the point that nuclear binding was possible, almost all first compound atomic nuclei to form were helium-4 nuclei. so tight was helium-4 binding that helium-4 production consumed nearly all of the free neutrons in a few minutes, before they could beta-decay, and also leaving few to form heavier atoms such as lithium, beryllium, or boron. helium-4 nuclear binding per nucleon is stronger than in any of these elements (see nucleogenesis and binding energy) and thus, once helium had been formed, no energetic drive was available to make elements 3, 4 and 5. it was barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon, carbon. however, due to lack of intermediate elements, this process requires three helium nuclei striking each other nearly simultaneously (see triple alpha process). there was thus no time for significant carbon to be formed in the few minutes after the big bang, before the early expanding universe cooled to the temperature and pressure point where helium fusion to carbon was no longer possible. this left the early universe with a very similar ratio of hydrogen/helium as is observed today (3 parts hydrogen to 1 part helium-4 by mass), with nearly all the neutrons in the universe trapped in helium-4.
helium