<P> In physical cosmology , Big Bang nucleosynthesis ( abbreviated BBN , also known as primordial nucleosynthesis , arch ( a ) eonucleosynthesis , archonucleosynthesis , protonucleosynthesis and pal ( a ) eonucleosynthesis ) refers to the production of nuclei other than those of the lightest isotope of hydrogen ( hydrogen - 1 , H , having a single proton as a nucleus ) during the early phases of the Universe . Primordial nucleosynthesis is believed by most cosmologists to have taken place in the interval from roughly 10 seconds to 20 minutes after the Big Bang , and is calculated to be responsible for the formation of most of the universe 's helium as the isotope helium - 4 ( He ) , along with small amounts of the hydrogen isotope deuterium ( H or D ) , the helium isotope helium - 3 ( He ) , and a very small amount of the lithium isotope lithium - 7 ( Li ) . In addition to these stable nuclei , two unstable or radioactive isotopes were also produced : the heavy hydrogen isotope tritium ( H or T ) ; and the beryllium isotope beryllium - 7 ( Be ) ; but these unstable isotopes later decayed into He and Li , as above . </P>
<P> In physical cosmology , Big Bang nucleosynthesis ( abbreviated BBN , also known as primordial nucleosynthesis , arch ( a ) eonucleosynthesis , archonucleosynthesis , protonucleosynthesis and pal ( a ) eonucleosynthesis ) refers to the production of nuclei other than those of the lightest isotope of hydrogen ( hydrogen - 1 , H , having a single proton as a nucleus ) during the early phases of the Universe . Primordial nucleosynthesis is believed by most cosmologists to have taken place in the interval from roughly 10 seconds to 20 minutes after the Big Bang , and is calculated to be responsible for the formation of most of the universe 's helium as the isotope helium - 4 ( He ) , along with small amounts of the hydrogen isotope deuterium ( H or D ) , the helium isotope helium - 3 ( He ) , and a very small amount of the lithium isotope lithium - 7 ( Li ) . In addition to these stable nuclei , two unstable or radioactive isotopes were also produced : the heavy hydrogen isotope tritium ( H or T ) ; and the beryllium isotope beryllium - 7 ( Be ) ; but these unstable isotopes later decayed into He and Li , as above . </P>
where did helium come from the early universe
where did helium come from the early universe
Primordial nucleosynthesis
Primordial nucleosynthesis