New Measurements of Ancient Deuterium Boost the Baryon Density of the Universe

AUG 01, 1996

A new search for primordial deuterium finds less than others had reported previously. The new results give some comfort to those who favor a closed universe.

DOI: 10.1063/1.881505

Bertram M. Schwarzschild

A side from ordinary hydrogen, only four other nuclear species ( ${}^{2}H,$ ${}^{3}{He},$ ${}^{4}{He}$ and ${}^{7}{Li}$ are left over from the Big Bang. Of these, deuterium $(^{2} H)$ is the one whose obsei^ved abundance provides the most accurate determination of the crucial cosmological parameter $ρ_{b},$ the present‐day average mass density of ordinary baryonic matter (made up of protons and neutrons) in the universe. In principle, if one knows the primordial abundance of any one of these light nuclei, relative to ${}^{1}H,$ the theory of Big Bang nucleosynthesis specifies $ρ_{b} .$ (See the figure below.)

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