The age of the Universe from a large sample of the oldest Galactic stars

8 hours ago

Researchers estimated the age of the Universe using a large sample of 247,103 Milky Way stars with high-resolution spectroscopy from LAMOST DR7 and Gaia eDR3 parallaxes.
After applying quality cuts, the final sample consisted of 155,600 stars within 5 kpc, with stellar ages estimated using YY isochrones up to 20 Gyr and cross-checked with FLAME ages from Gaia data.
Using an MCMC reconstruction of the latent age distribution, the oldest star's age was found to be A_★ = 13.73^{+0.18}_{-0.15} Gyr, with variations due to quality cuts ranging from 13.31 to 14.02 Gyr.
The inferred cosmic age is consistent with the 13.6 Gyr expected from CMB-calibrated ΛCDM cosmology, assuming the first long-lived stars formed when the Universe was 0.2 Gyr old.
This agreement challenges solutions to the Hubble tension based solely on new physics before recombination, which typically predict a lower cosmic age of about 12.9 ± 0.2 Gyr.
Stellar modeling uncertainties are unlikely to reconcile such a low age with the results, given the low metallicities of the oldest stars and independent asteroseismic constraints.

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