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 2, 2026

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Simply

By carefully sifting through a huge number of old Milky Way stars and using clever statistics, the paper found the oldest star is about 13.7 billion years old, which helps confirm the Universe's age and challenges ideas that try to fix the Hubble tension by changing how the early Universe expanded.

In depth

The paper refines the age of the Universe by analyzing a large sample of old Milky Way stars. It introduces population-level quality cuts and an MCMC reconstruction of the latent age distribution to robustly estimate the age of the oldest star,

A_{⋆}

, which provides a lower limit for the Universe's age. This estimate challenges early-time solutions to the Hubble tension.

Key Takeaways

1
The study estimates the age of the oldest Galactic star, $A_{⋆}$ , to be $13.7 3_{- 0.15}^{+ 0.18}$ Gyr using MCMC reconstruction of stellar age distributions.
2
It introduces innovative population-level quality cuts based on stellar chemistry and cross-catalogue age consistency to refine the sample of old stars.
3
The inferred $A_{⋆}$ is consistent with CMB-calibrated $Λ$ CDM predictions but creates significant tension with early-time solutions to the Hubble tension.

Conceptual Flow

HIGH LEVEL

Refining Stellar Ages for Cosmic Insights

The study carefully selects a large group of old stars and uses advanced statistics to figure out the true age of the oldest one, even with fuzzy measurements.

Raw Star Data

Initial Age Estimates

Clean & Analyze

Oldest Star's Age

Cosmic Age Confirmed, Hubble Tension Challenged

The age found for the oldest star matches what's expected from the early Universe, making it harder for theories that suggest the Universe expanded much faster early on.

Oldest Star Age

CMB Expected Age

Early-Time Theory Age

Compare & Evaluate

CMB Age Matches

Early-Time Theory Disfavored