The oldest known star seems to be older than the universe itself, but a fresh study is facilitating to clear up this apparent enigma.
Earlier study had projected that the Milky Way galaxy's so-called "Methuselah star" is up to 16 billion years old. That's a problem, as most scientists agree that the Big Bang that made the universe happened about 13.8 billion years ago. Now a team of astrophysicists has derived a new, less ridiculous age for the Methuselah star, combining information about 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," study chief author Howard Bond, of Pennsylvania State University and the Space Telescope Science Institute in Baltimore, said in an announcement.
The uncertainty Bond refers to is plus or minus 800 million years, which means the star could truly be 13.7 billion years old — younger than the cosmos as it's presently understood, though just barely.
A mysterious, fast-moving star:
Bond and his team utilized NASA's Hubble Space Telescope to study the Methuselah star, which is more officially known as HD 140283. Researchers have known about HD 140283 for more than 100 years, as it journeys across the sky at a comparatively rapid clip. The star moves at around 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, scientists said.
The star is just passing through the Earth's neck of the galactic woods and will ultimately rocket back out to the Milky Way's halo, a populace of earliest stars that surrounds the galaxy's acquainted spiral disk. The Methuselah star, which is just now swelling into a red giant, was perhaps born in a dwarf galaxy that the nascent Milky Way gobbled up more than 12 billion years ago, scientists said. The star's long, looping orbit is possibly a residue of that intense act of cannibalism.
Distance makes the difference:
Hubble's calculations permitted the astrophysicists to polish the distance to HD 140283 using the principle of parallax, in which a change in an observers' location — in this case, Hubble's variable position in Earth orbit — translates into a shift in the deceptive position of an object.
They discovered that Methuselah lies 190.1 light-years away. With the star's distance known more accurately, the team was capable of working out Methuselah's intrinsic brightness, a need for calculating its age.
The researchers also applied present theory to learn more about the Methuselah star's burn rate, composition and internal structure, which also shed light on its possible age. For an instant, HD 140283 has a comparatively high oxygen-to-iron ratio, which takes the star's age down from some of the former estimates, scientists said.
In the end, the astrophysicists estimated that HD 140283 was born 14.5 billion years ago, plus or minus 800 million years. Additional studies could help bring the Methuselah star's age down even more, making it clearly younger than the universe, scientists said.