Methuselah Star's 14.2 Billion-Year Age Prompts Continued Scrutiny of Cosmic Chronology

The Methuselah Star, formally known as HD 140283, continues to intrigue astronomers with its advanced age, which has, at times, appeared to exceed that of the universe itself. As noted by Brian Roemmele on social media, "> The Methuselah Star located in our own galaxy is thought to be about a billion years older than the universe. Yes a single star older than our universe. So either our theories are off or we have been blessed with anomalous single star that lasted the last universe collapse…". This statement encapsulates a long-standing astronomical puzzle.

Initially estimated to be as old as 16 billion years in the early 2000s, HD 140283 presented a significant challenge to the then-accepted age of the universe, which is approximately 13.8 billion years. Located about 200 light-years away in the constellation Libra, this metal-poor subgiant is considered one of the oldest stars known, composed primarily of hydrogen and helium, indicating its formation in the very early cosmos.

Subsequent refinements in observational techniques, particularly using the Hubble Space Telescope's Fine Guidance Sensors, helped narrow down the star's age. By precisely measuring its distance and luminosity, astronomers, including Howard Bond, revised the estimate to 14.46  0.8 billion years. The crucial inclusion of an 800-million-year uncertainty margin allowed the star's age to overlap with the universe's age, largely resolving the initial paradox. A 2025 asteroseismic analysis further refined the star's age to 14.2  0.4 billion years, maintaining compatibility within error bars.

Despite these reconciliations, new cosmological measurements have introduced fresh complexities. Discrepancies in the Hubble Constant, which measures the universe's expansion rate, suggest that the universe might be younger than 13.8 billion years, with some estimates proposing an age as low as 11.4 billion years. If these lower estimates for the universe's age prove accurate, the Methuselah Star would once again appear to predate its cosmic environment, reigniting the debate.

The ongoing study of HD 140283 and the varying estimates for the universe's expansion rate underscore fundamental questions in astrophysics and cosmology. Scientists are actively working to refine these measurements, with future observations from instruments like the James Webb Space Telescope expected to provide critical data. Resolving these age paradoxes is vital for a comprehensive understanding of the universe's origins and evolution.