Monday, January 14, 2013

Nearby star is almost as old as the Universe

Astronomers have discovered a Methuselah of stars — a denizen of the Solar System's neighbourhood that is at least 13.2 billion years old and formed shortly after the Big Bang.
“We believe this star is the oldest known in the Universe with a well determined age,” says Howard Bond, an astronomer at Pennsylvania State University in University Park, who announced the finding on 10 January at a meeting of the American Astronomical Society in Long Beach, California1.

The venerable star, dubbed HD 140283, lies at a comparatively short distance of 190 light years from the Solar System and has been studied by astronomers for more than a century. Researchers have long known that the object consists almost entirely of hydrogen and helium — a hallmark of having formed early in the history of the Universe, before successive generations of stars had a chance to forge heavier elements. But no one knew exactly how old it was.

Old timer

Determining the star’s age required several steps. First, Bond and his team made a new and more accurate determination of the star’s distance from the Solar System, using 11 sets of observations recorded between 2003 and 2011 using the Hubble Space Telescope’s Fine Guidance Sensors, which measure the position of target stars relative to reference stars. The astronomers also measured the brightness of the star as it appears in the sky, and were then able to calculate its intrinsic luminosity.

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