The Mystery of the Oldest Star in the Universe

Astrophiles are well aware that the age of the universe is approximately 13.8 billion years old, meaning no celestial bodies within it can be older than this age. However, in the vast expanse of the cosmos, a star identified as “HD 140283” has garnered attention from astronomers due to its exceptionally ancient characteristics.

Affectionately dubbed the “Methuselah Star” after the character in the Bible who lived for 969 years, hinting at its extreme age, this star poses perplexing questions. Methuselah Star, located in the direction of Libra, about 200 light-years away from us, with a mass approximately 0.81 times that of the Sun and a radius around 2.04 times that of the Sun, is currently in a subgiant stage on the brink of becoming a giant star. Despite its visual magnitude of only 7.2, it can still be admired through regular telescopes. Astronomers first discovered this unique star in 1912, and subsequent observational data revealed that Methuselah Star is predominantly composed of hydrogen and helium, indicating its ancient origins.

In the early stages of the universe, elements heavier than hydrogen and helium were extremely scarce, suggesting that Methuselah Star, consisting almost entirely of hydrogen and helium, likely originated in the early universe. This discovery piqued astronomers’ interest, leading them to attempt to estimate the star’s age. However, due to observational limitations, Methuselah Star’s age remained a mystery.

It wasn’t until the year 2000 that astronomers, utilizing data from the European Space Agency’s “Hipparcos high-precision parallax satellite,” first estimated that Methuselah Star formed approximately 16 billion years ago. This revelation was shocking as the formation of the universe itself is commonly believed to have occurred around 13.8 billion years ago. Such an estimation fueled widespread confusion and skepticism, seeming contradictory to our understanding of the universe’s origin and evolution.

To unravel this enigma, a research team led by astronomer Howard Bond from Penn State University meticulously analyzed years of observation data from the Hubble Space Telescope and reappraised Methuselah Star’s age using various scientific measurement methods. Eventually, they estimated the star’s age to be 13.9 billion years. Despite still exceeding the universe’s age, the research team acknowledged a 700 million-year uncertainty range in the estimation process. This implies that Methuselah Star’s age could be as low as 13.2 billion years, thereby averting a direct conflict with the universe’s age.

Nonetheless, not everyone found this explanation satisfactory. Some scientists questioned the use of the “uncertainty range,” deeming this explanation somewhat forced. They pointed out that this range could be employed to decrease or increase Methuselah Star’s age, and the research team chose to reduce the age to avoid conflicting with the universe’s age.

As observational techniques continue to advance, new issues have surfaced. In recent years, astronomers have discovered through new measurement methods that the “Hubble constant” may be larger than previously believed. The Hubble constant describes the rate of the universe’s expansion, upon which the universe’s age is calculated. If the value of the Hubble constant increases, the rate of cosmic expansion accelerates, leading to a decrease in the universe’s age.

According to the latest estimates, with a Hubble constant value of 74, the age of the universe is approximately 12.7 billion years. If the value is 82.4, the universe’s age could be as low as 11.4 billion years. This implies that even with the research team’s lowest age estimation, Methuselah Star remains older than the universe itself.

The paradox between Methuselah Star and the age of the universe remains unsolved to this day. While astronomers endeavor to reevaluate the age of stars and the rate of cosmic expansion through various methods and observational data, this mystery continues to perplex scientists.

Perhaps with the further development of future observational technologies and the introduction of new scientific theories, we may gradually uncover the truth behind this ancient puzzle. Until then, Methuselah Star will continue to shine in the cosmos, serving as a crucial clue for astronomers exploring the origins and evolution of the universe.