The aging star, cataloged as HD 140283, lies 190.1 light-years away from Earth.
"We have found that this is the oldest known star with a well-determined age," said Howard Bond of Pennsylvania State University and the Space Telescope Science Institute in Baltimore.
The star could be as old as 14.5 billion years, astronomers said, which is a bit of a puzzle since the calculated age of the universe is about 13.8 billion years.
But it's a better estimate than previous observations that had put the star's age as old as 16 billion years, Bond said, a real dilemma for cosmologists.
"Maybe the cosmology is wrong, stellar physics is wrong or the star's distance is wrong," Bond said. "So we set out to refine the distance."
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.