Located approximately 190 light-years away in the constellation Libra is an unassuming star known as HD 140283; with an apparent magnitude of around 7, it is generally invisible to the naked eye.

Scientific estimates place the age of this star at an astonishing figure exceeding 14 billion years. Given that the estimated age of the universe is approximately 13.8 billion years, a seemingly paradoxical question arises: "Is HD 140283 truly older than the universe itself?" Due to its remarkable age, the star has earned the nickname "Methuselah Star."

What kind of star is HD 140283?

HD 140283 is an extremely old, metal-poor subgiant that has already left the main sequence and begun the next stage of stellar evolution. In astronomy, "metals" refer to elements other than hydrogen and helium, and HD 140283 has an iron abundance that is only a tiny fraction of the Sun's. This is significant because the early universe consisted almost entirely of hydrogen, helium, and trace amounts of lithium; heavier elements such as carbon, oxygen, and iron required nuclear fusion within earlier generations of stars and supernova explosions to be produced in substantial quantities. Generally, the lower a star's metal content, the more likely it originated in the early universe; thus, HD 140283's chemical composition serves as key evidence of its extreme age.

Why is it called the "Methuselah star"?

The name derives from the biblical figure Methuselah, who was renowned for his extreme longevity—a name often used to describe things of exceptional age. HD 140283 earned this nickname primarily due to a precise age determination announced in 2013; researchers used the Hubble Space Telescope to accurately measure the star's parallax and, by combining this data with its brightness, temperature, chemical composition, and stellar evolution models, calculated a central age estimate of approximately 14.46 billion years, with an overall margin of error of about 800 million years. Because this figure exceeds the age of the universe—estimated at around 13.8 billion years—the label "star older than the universe" quickly became its most widely known moniker.

How is the age of a star determined?

Astronomers cannot directly determine a star's actual age by simply counting rings, as one might with a tree; instead, they rely on scientific estimation methods. For a subgiant star like HD 140283, the process begins by measuring its distance from Earth and calculating its true luminosity based on its apparent brightness. This information is then combined with data on surface temperature, mass, metallicity, and oxygen content, and the resulting dataset is compared against stellar evolution models.

Stars in the subgiant phase are particularly well-suited for age determination because, after leaving the main sequence, their brightness changes in a way that is highly sensitive to age. However, this sensitivity also means that even slight adjustments to parameters such as distance, chemical abundance, nuclear reaction rates, or model settings can shift the estimated age by hundreds of millions of years. The figure of "14.46 billion years" is essentially an estimate subject to statistical and model-based uncertainties, rather than a precise date of birth.

The Methuselah star is not actually older than the universe.

Scientific measurements must be understood in conjunction with their margins of error. Although the initial estimate of 14.46 billion years exceeded the age of the universe, factoring in an uncertainty of approximately 0.8 billion years placed the lower end of the range within a span compatible with the universe's age; consequently, the original study did not claim the discovery of a "star formed before the universe." Subsequent refinements to stellar models have led to adjustments or reductions in the estimated age.

A 2025 study in asteroseismology utilized TESS to detect stellar oscillations in HD 140283; by combining this data with new models, researchers estimated its age at approximately 14.2 ± 0.4 billion years. While this result remains extremely old, it is consistent with the age of the universe within the 1σ margin of error.

Is HD 140283 a first-generation star?

Despite its extreme age, HD 140283 is generally not considered a true first-generation star (Population III star). Theoretically, first-generation stars formed in the earliest stages of the universe; composed primarily of hydrogen and helium left over from the Big Bang, they contained virtually no heavy elements. Many were likely massive and short-lived, dispersing newly synthesized elements—such as carbon, oxygen, and iron—into the interstellar medium upon exploding. Although HD 140283 is metal-poor, it still contains measurable amounts of heavy elements, implying that the gas from which it formed had already been "polluted" by an even earlier generation of stars. Consequently, it is more likely a second-generation or very early-generation star, serving as a crucial "fossil" for studying how the first stars influenced the subsequent chemical evolution of the Milky Way.

Can HD 140283 be observed from North America?

HD 140283 is located in the constellation Libra, with coordinates of approximately 15h 43m right ascension and −10°56′ declination; consequently, the region of the sky where it resides is visible from most parts of the United States and Canada. Although it lies about 190 light-years from Earth, its apparent magnitude is only around 7.2—beyond the limit of the naked eye under typical sky conditions—so binoculars or a small telescope are usually required for viewing. The real challenge in observing it is not the equipment itself, but the fact that HD 140283 appears as nothing more than an ordinary, faint star, lacking any distinctive color or structure discernible to the naked eye. Therefore, rather than attempting to locate it by simply guessing based on the description "a faint star near Libra," it is best to use a detailed star chart or astronomy software to pinpoint its exact coordinates.

What does the Methuselah star really tell us?

The so-called "star older than the universe" actually serves as an excellent example for understanding scientific measurement methods. While HD 140283 is undoubtedly one of the oldest and most thoroughly studied stars in the Milky Way, its age is not a fixed figure devoid of uncertainty. As measurements involving parallax, elemental abundance, stellar evolution models, and asteroseismology continue to improve, age estimates become increasingly refined. When discussing the age of the Methuselah star—how old HD 140283 is and why it appears older than the universe—the most accurate conclusion is that it formed in the very early universe, yet there is no reliable evidence suggesting it predates the universe itself; what truly merits our attention is the history of the early universe that this ancient star has preserved for us.