Hubble finds ‘birth certificate’ of oldest known star

Artist's impression of a star that appeared to be older than the Universe. Naturally, astronomers were not happy.
Credit: Nasa/Hubble Space Telescope
Date:8 March 2013 Tags:, ,

A team of astronomers using Nasa’s Hubble Space Telescope has taken an important step closer to finding the “birth certificate” of a star that’s been around for a very long time – longer than anything in the known Universe, in fact. Here’s the thing: the star could be as old as 14,5 billion years (plus or minus 0,8 billion years), which at first glance would make it older than the Universe’s calculated age of about 13,7 billion years – an obvious problem for astronomers.

Years ago, the dilemma was even worse: back then, observations suggested the so-called “Methuselah star” could be as old as 16 billion years. But astronomer Howard Bond of Pennsylvania State University and the Space Telescope Science Institute in Baltimore provides some useful perspective: “Maybe the cosmology is wrong, stellar physics is wrong, or the star’s distance is wrong,” he says. “So we set out to refine the distance.”

The new Hubble age estimates reduce the range of measurement uncertainty so that the star’s age at least overlaps with that of the Universe — as independently determined by the rate of expansion of space, an analysis of the background microwave radiation from the Big Bang, and measurements of radioactive decay..

Catalogued as HD 140283, it has been known about for more than a century because of its fast motion across the sky – evidence that it 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. It was probably born in a primeval dwarf galaxy that was gravitationally shredded and sucked in by the emerging Milky Way over 12 billion years ago.

This conclusion was bolstered by 1950s astronomers who were able to measure a deficiency of heavier elements in the star as compared with other stars in our galactic neighborhood. The halo stars are among the first inhabitants of our galaxy and collectively represent an older population from the stars, such as our Sun, that formed later in the disc. This means that the star – which is at the very early stage of expanding into a red giant – formed at a very early time, before the Universe was largely “polluted” with heavier elements forged inside stars through nucleosynthesis.  — Source: Nasa/Hubble Space Telescope

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