Question: where did helium come from the early universe
Answer: 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 ) .