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HubbleSite Hubble Finds Birth Certificate of Oldest Known Star


Space Telescope Science

You can't be older than your parents. But there is a nearby star that at first glance looks like it is older than the universe! Hubble Space Telescope astronomers are coming to grips with this paradox by improving the precision of the observations used to estimate the age of this "Methuselah star."

Around the year 2000, estimates for the star's age were about 16 billion years. But the universe is about 13.8 billion years old, based on a meticulous calibration of the expansion of space and analysis of the microwave afterglow from the big bang. Hubble data and improved theoretical calculations were used to recalculate the star's age and lower the estimate to 14.5 billion years, within a measurement uncertainty of plus or minus 800 million years. This places the star within a comfortable range to be younger than the universe. Astronomers have to collect a lot of information to deduce a star's age because it doesn't come with a birth certificate. They have to take into account where the star is in its life history, the detailed chemistry of the star, and its intrinsic brightness. Hubble's contribution was to reduce the uncertainty on the star's true distance. With that improved accuracy, the intrinsic brightness of the star is better known. The ancient star is still spry for its age. It is speeding past us at 800,000 miles per hour. Its orbit can be traced back to the halo of our galaxy, which is a "retirement home" for stars that were born long before the Milky Way was even fully assembled.

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