The Hubble tension is one of the biggest unsolved puzzles in modern cosmology. The Hubble constant, which is a number that measures the rate at which the universe is expanding today, has been calculated using different techniques.
The first is the local distance ladder measurements, which observe nearby galaxies and use measurements that suggest that the universe expands faster and is younger. The second is the early universe measurement, which analyzes radiation from the early universe called the cosmic microwave background, suggesting that the universe expands more slowly and is older. This has created a disparity in calculations called the Hubble tension.
Instead of measuring the expansion rate, astronomers analyzed an existing catalogue of stellar ages, which provides more reliable information on the age of the universe. Data from the powerful European Space Agency’s Gaia mission were collected. Gaia measures stellar parallax, which determines distance with extremely high precision. A catalog containing the stellar ages of over 200,000 Milky Way stars was analyzed, and only data from the oldest and most reliable stars were used.
From the analysis, the most probable cosmic age was placed at 13.6 billion years. This estimate is closely aligned to the cosmic age derived from the cosmic microwave background. However, this does not completely solve the Hubble tension yet due to uncertainties in stellar evolution models, age estimation techniques, and chemical composition measurements. Future Gaia data releases will significantly reduce these uncertainties, determining the age of the universe with higher precision.