Oldest known star appears older than the universe itself

March 08, 2013

Oldest known star appears older than the universe itself

An old star gets a little younger.

It’s a finding that has astronomers puzzled: the oldest known star appears older than the universe itself.

Yes, you read that right.

According to a newly released report, an aging star — dubbed HD 140283 — lies 190.1 light-years away from Earth and is reportedly 14.5 billion years old. The problem? The calculated age of the universe is about 13.8 billion years.

The finding is largely the result of a margin of error baked into the calculation. Using the Hubble Space Telescope, astronomers were able to refine the star’s age to about 14.5 billion years, plus or minus 800 million years. The margin of error shows the star could have formed during a short period after the big bang, the most likely scenario considering the alternatives.  Previous estimates of the star’s age had sitting around sixteen billion years, just over two billion years older than the universe itself.

Still, the finding has left some astronomers stunned.

“Maybe the cosmology is wrong, stellar physics is wrong or the star’s distance is wrong,” said Howard Bond of Pennsylvania State University and the Space Telescope Science Institute in Baltimore.

“You get an age of 14.5 billion years, with a residual uncertainty that makes the star’s age compatible with the age of the universe,” he added. “This is the best star in the sky to do precision age calculations by virtue of its closeness and brightness.”

The astronomers said the range of measurement uncertainty they encountered — plus or minus 800 million years — could lower the upper age limit, which would make the star unequivocally younger than the universe.

“Put all of those ingredients together and you get an age of 14.5 billion years, [but] with a residual uncertainty that makes the star’s age compatible with the age of the universe,” Bond said.

The team of astronomers were able to revise the star’s age after using Hubble to judge the distance of the star from Earth using trigonometric parallax — a syllable-heavy way of describing how a star’s position appears to change depending on the position of the observer. In comparing the observations from opposite points in Hubble’s orbit around Earth, astronomers were able to deduce a better approximation of the star’s distance. The information was then combined with information with information on the star’s intrinsic brightness, providing astronomers with nearly five-fold increase in the accuracy of the star’s age.

The “Methuselah star” has been known about for more than a century because of its fast motion across the sky. The high rate of motion is evidence that the star is simply a visitor to our stellar neighborhood. Its orbit carries it down through the plane of our galaxy from the ancient halo of stars that encircle the Milky Way, and will eventually slingshot back to the galactic halo.

The star is the oldest object currently known to astronomers and it’s likely that it will remain a presence for at least the coming million years. Astronomers say the star is just beginning to enter its red giant phase.

The finding is the latest study related to the age of the universe. A recently released study revised the distance between Earth and a pair of binary stars, presenting astronomers with a new standard for measuring objects across the universe. The change could change a number of previously accepted distances between objects in our own galaxy and beyond.


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