Thaindian News

Washington, May 25 (IANS) For many movie stars, their age is a well-kept secret. The same is true of the actual stars in space.

Like our sun, most stars look almost the same for most of their lives. So how can we tell if a star is one billion or 10 billion years old? Astronomers may have found a solution - by measuring the star’s spin.

“A star’s rotation slows down steadily with time, like a top spinning on a table, and can be used as a clock to determine its age,” says astronomer Soren Meibom of the Harvard-Smithsonian Centre for Astrophysics.

Knowing a star’s age is important for many astronomical studies and in particular for planet hunters. With the bountiful harvest from NASA’s Kepler spacecraft (launched in 2009) adding to previous discoveries, astronomers have found nearly 2,000 planets orbiting distant stars.

Now, they want to use this new zoo of planets to understand how planetary systems form and evolve and why they are so different from each other. The study is scheduled for publication in The Astrophysical Journal Letters.

“Ultimately, we need to know the ages of the stars and their planets to assess whether alien life might have evolved on these distant worlds,” says Meibom, according to a Harvard statement.

“The older the planet, the more time life has had to get started. Since stars and planets form together at the same time, if we know a star’s age, we know the age of its planets too.”

Learning a star’s age is relatively easy when it’s in a cluster of hundreds of stars that all formed at the same time. Astronomers have known for decades that if they plot the colours and brightness of the stars in a cluster, the pattern they see can be used to tell the cluster’s age.

But this technique only works on clusters. For stars not in clusters (including all stars known to have planets), determining the age is much more difficult. Using the unique capabilities of the Kepler space telescope, Meibom and his collaborators measured the rotation rates for stars in a one-billion-year-old cluster called NGC 6811.

These findings were presented at the 218th meeting of the American Astronomical Society.