Big Bang Nucleosynthesis

• Light elements (namely deuterium, helium, and lithium) were produced in the first few minutes of the Big Bang

• Elements heavier than 4He are produced in the stars and through supernovae

• However, enough helium and deuterium cannot be produced in stars to match what is observed because stars destroy deuterium in their cores

• So all the deuterium we see must have been made around three minutes after the big bang, when T~109 K

• BBN predicts that 25% of the matter in the Universe should be helium, and about 0.001% should be deterium, which is what we see