This Star is older than the Universe

The oldest known star appears to be older than the cosmos itself, but a new study is helping to solve this apparent mystery.

An earlier study estimated that the so-called "Methuselah star" in the Milky Way galaxy is up to 16 billion years old. This is a concern because most scientists think that the Big Bang that created the universe occurred approximately 13.8 billion years ago. A team of astronomers has now calculated a new, less absurd age for the Methuselah star by combining data on its distance, brightness, composition, and structure.

"Put all of those constituents together, and you get an age of 14.5 billion years, with a remaining doubt that makes the star's age compatible with the age of the cosmos," said study lead author Howard Bond of Pennsylvania State University and the Space Telescope Science Institute in Baltimore in a statement.

Bond refers to an uncertainty of 800 million years, which indicates the star may be 13.7 billion years old – younger than the cosmos as it is currently understood, but only just.

A mysterious and swiftly moving star:

Bond and his colleagues studied the Methuselah star, also known as HD 140283, using NASA's Hubble Space Telescope. HD 140283 has been known to scientists for more than a century, as it travels across the sky at a quite fast rate. According to astronomers, the star moves at roughly 800,000 mph (1.3 million km/h) and covers the width of the full moon in the sky every 1,500 years or so.

The star is simply passing through Earth's galactic neck of the woods and will eventually rocket back out to the Milky Way's halo, a population of early stars that surrounds the galaxy's well-known spiral disc. According to astronomers, the Methuselah star, which is just now forming into a red giant, was likely born in a dwarf galaxy that the young Milky Way devoured more than 12 billion years ago. The star's extended, looping orbit could be a leftover from that furious act of cannibalism.

The difference is determined by distance:

The astrophysicists were able to refine the distance to HD 140283 by employing the principle of parallax, which states that a change in an observer's location — in this case, Hubble's fluctuating position in Earth orbit — results as a shift in the false position of an object.

Methuselah is 190.1 light-years away, they discovered. With the star's distance more precisely determined, the team was able to calculate Methuselah's intrinsic brightness, which was required for measuring its age.

The researchers also used current theory to understand more about the burn rate, composition, and interior structure of the Methuselah star, which offered light on its likely age. For example, HD 140283 has a relatively high oxygen-to-iron ratio, which reduces the star's age from some previous estimates, according to astronomers.

Finally, astrophysicists calculated that HD 140283 was born 14.5 billion years ago, plus or minus 800 million years. Additional research could help reduce the age of the Methuselah star even further, making it demonstrably younger than the cosmos, according to scientists.