Scientists Measure Age of Universe

L O N D O N, Feb. 8 -- A team of international scientistsmay have found the answer to a question that has baffledastronomers for centuries: how old is our universe?

At least 12.5 billion years old, give or take a few billionyears, according to new research published in the sciencejournal Nature Wednesday.

Roger Cayrel, of the Paris-Meudon Observatory in France, andhis colleagues in Europe, South America and the United States calculated the age of the universe by taking a differentapproach.

Instead of measuring the expansion rate of the universe orthe velocities of distant stars, they measured amounts of theradioactive elements thorium and uranium in an ancient starnamed CS31082-001 using a technique called radioactivecosmochronometry.

"The ages of the oldest stars in the galaxy indicate whenstar formation began and provide a minimum age for theuniverse," Cayrel said in a study.

By their best calculations CS31082-001 is about 12.5 billionyears old, with an error factor of about three billion years.

In a commentary on the research, Christopher Sneden of theUniversity of Texas in Austin described the study as a majoradvance in radioactive cosmochronometry.

"We may expect to find more examples of such stars, as oursurvey of the galactic halo with the new generation of verylarge telescopes is just beginning," he said.

"With new discoveries, more age estimates will be found,further nailing down the exact age of the universe."