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NUCLEAR ASTROPHYSICS

Deuterium experiments reveal conditions in the early Universe

Nature Reviews Physics volume 2, page 664 (2020)Cite this article

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A Publisher Correction to this article was published on 24 November 2020

This article has been updated

Measuring the amount of deuterium (hydrogen-2) in astrophysical gas clouds gives a window into the first few minutes of the Universe. The deuterium, along with other light elements such as helium, was produced in a sequence of nuclear reactions known as Big Bang nucleosynthesis (BBN). The theoretical prediction for how much deuterium was produced is sensitive to the primordial density of baryons (such as protons and neutrons) — the only fitting parameter of the standard theory for BBN. However, the window to the early Universe is clouded. Although it would seem that fitting theory to observations would give a precise value for an important cosmological parameter, the fit is hampered by uncertainties in the cross section of the deuterium burning process, in which a deuterium nucleus and a proton combine to form a helium-3 nucleus. Writing in Nature, Viviana Mossa and colleagues lay some of the uncertainty to rest, reporting improved cross sections for deuterium burning that lead to a clearer picture of the early Universe.

Having a better cross section for deuterium burning also puts constraints on alternative models. The value of the baryon density at 380,000 years after the Big Bang can be obtained by measuring anisotropies in the cosmic microwave background (CMB). The standard model of cosmology predicts that the values of baryon density obtained from BBN and CMB should be the same, and the value obtained by Mossa et al is indeed closer to the CMB value than previous measurements were. It is also possible to put a limit on the amount of ‘dark radiation’ due to unknown particle species by using both the baryon density and the effective number of neutrino species as fitting parameters in the BBN model. Making such a fit using the new deuterium burning cross section gives a limit that is in line with data from the Planck mission.

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Change history

  • 24 November 2020

    An Erratum to this paper has been published: https://doi.org/10.1038/s42254-020-00263-5.

References

Original article

  • Mossa, V. et al. The baryon density of the Universe from an improved rate of deuterium burning. Nature 587, 210–213 (2020)

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  1. Nature Reviews Physics https://www.nature.com/natrevphys/

    Zoe Budrikis

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  1. Zoe Budrikis
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Correspondence to Zoe Budrikis.

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Budrikis, Z. Deuterium experiments reveal conditions in the early Universe. Nat Rev Phys 2, 664 (2020). https://doi.org/10.1038/s42254-020-00260-8

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  • DOI: https://doi.org/10.1038/s42254-020-00260-8

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