Astrophysicists achieve record accuracy in primordial helium measurement

An international team of astrophysicists has achieved a record-breaking measurement of the amount of primordial helium formed during the first five minutes following the Big Bang. By reducing the margin of error to 0.5%, the researchers have improved the accuracy of this cosmological parameter by three times compared to previous attempts.

The study, known as the LBT Yp Project, utilized 130 hours of observations from the Large Binocular Telescope in Arizona. Researchers focused on 15 chemically primitive dwarf galaxies that act as cosmic time capsules, preserving traces of the early universe. The analysis involved more than 25 spectral lines of helium and hydrogen to isolate systematic effects that had hindered previous measurements.

The findings, published as a series of five papers in The Astrophysical Journal, yield a helium-4 mass fraction of Yp = 0.2458 ± 0.0013. This result aligns with the predictions of standard Big Bang nucleosynthesis (BBN) based on Planck data, reinforcing the established cosmological model and placing stricter constraints on potential new physics, such as additional light particles or non-standard early expansion scenarios.