Scientists shed light on age of the stars

The oldest stars are three billion years younger than previously thought, according to a group of US scientists who put their estimated age at a sprightly 9.6 billion years.

This discovery is as significant to cosmic physicists as the arrival of a government official at the door announcing the good news that you are actually younger than your birth certificate says.

It potentially solves one of the single biggest problems in our understanding of the creation of the universe: why some stars seemed to be older than the universe in which they sat.

"Up until now this has been a paradox," said Prof Mark Bailey, director of the Armagh Observatory.

This age contradiction represented a "fatal objection", he said, to one of the most popular theories of how the universe formed, the Big Bang theory. This holds that all the matter in the universe used to exist as a lump that blew apart in a truly big bang. Time also began at this instant and has been ticking steadily ever since.

The stuff that was thrown out by the explosion eventually lumped together to form galaxies, stars and planets, and these, including our own galaxy, are all still moving away from the explosion. Measurements of the expansion rate of the universe, known as the Hubble Constant, suggested that the universe, and hence the Big Bang, occurred between eight and 11 billion years ago.

The problem with this handy theory was that calculations of the age of the oldest stars in what are knows as globular clusters indicated they were formed 12 or 13 billion years ago, making them older than the universe.

The age of the oldest stars was "a real problem", Prof Bailey said. "They cast doubt on the whole Big Bang paradigm."

Professors Lawrence Krauss and Peter Kernan from Case Western Reserve University in Ohio, in collaboration with colleagues at Yale University and Steward Observatory, Arizona, believe they have overcome this difficulty.

They used new information gathered by the Hipparcos satellite which recorded the positions of the stars with unprecedented precision, and which also allowed a recalculation of their distances away. They concentrated on stars in 17 old-star clusters on the edges of our Milky Way galaxy and concluded that they were farther away than assumed.

"If it turns out that the research stacks up, then this allows one to breathe a sigh of relief that the stars are younger than the universe," Prof Bailey said. Dissenters to the Big Bang theory would not be put out of business by these findings. But until someone came up with something better, the Big Bang theory looked safe for now, he suggested.