Astrophysics

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

Indranil Banik, Thenujaya Kudakolawa Kaluarachchige, Stephen Cookson, Harry Desmond

Featured July 11, 2026

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Simply

Scientists looked at many old stars in our galaxy, carefully cleaning their data to find the true age of the oldest star, which helps figure out how old the whole Universe is, finding it matches what other big telescopes see.

In depth

The paper estimates the age of the Universe by precisely determining the age of the oldest stars in the Milky Way. They use a large sample of stars from LAMOST DR7 and Gaia eDR3, applying innovative population-level quality cuts to remove problematic age estimates. A Markov Chain Monte Carlo (MCMC) reconstruction of the latent age distribution then rigorously infers the maximum stellar age, providing a lower limit for the cosmic age.

Key Takeaways

1
The study uses a large sample of 155,600 Milky Way stars with high-resolution spectroscopy and astrometry to estimate the age of the oldest star ( $A_{⋆}$ ).
2
They introduce population-level quality cuts based on age-metallicity and age- $α$ -element relations, and cross-catalogue age consistency, to ensure reliable stellar age estimates.
3
An MCMC reconstruction of the latent age distribution, combined with a novel $P / σ$ analysis, yields $A_{⋆} = 13.7 3_{- 0.15}^{+ 0.18}$ Gyr, consistent with CMB-calibrated $Λ$ CDM.

Conceptual Flow

HIGH LEVEL

Methodology (The "Logic")

The scientists gathered star data, cleaned it carefully to remove bad measurements, and then used a smart computer method to find the true age of the oldest stars.

Star Data

Age Estimates

Clean & Analyze

Oldest Star Age

Results (The "Impact")

They found the oldest star is about 13.7 billion years old, which fits well with the age expected from the early Universe, challenging ideas that the Universe expanded much faster early on.

Oldest Star Age

Expected Age (CMB)

Expected Age (Local)

Compare Ages

Matches CMB Age

Tension with Local Age