Consistency of the primordial abundance of 4He with the predictions of big bang nucleosynthesis provides a key test of the standard model of cosmology. Recent calculations predict that the primordial mass fraction of 4He, Yp, should exceed 0.236. The helium abundances determined from the observations of 38 metal-poor extragalactic H II regions are used to infer a 95% CL statistical upper bound to Yp which, depending on the specific method employed to extrapolate the data, and/or the subsets of data used in 1, 2, 3, or 4 parameter fits, yields Yp ≤ 0.237-0.243.
- Early universe
- Nebulae: H II regions