Scientists Discover the True Age of Stars by Studying Their Spin

There may be a new way to tell the age of stars. As stars grow older, they slow down in terms of their spin. Now, astronomers are taking advantage of this fact to tackle stellar ages.

"Our goal is to construct a clock that can measure accurate and precise ages of stars from their spins," said Soren Meibom, one of the researchers, in a news release. "We've taken another significant step forward in building that clock."

When stars are young, they rotate more quickly and have larger sunspots. As they age, though, they slow down, and that makes it more difficult to determine exactly how old they are. Knowing a star's age is particularly relevant to the search for signs of alien life outside of our solar system. With an accurate stellar clock, astronomers could potentially identify stars that are most likely to have planets that can host life.

Astronomers looked for changes in a star's brightness caused by dark spots on its surface in order to measure its spin. Unlike our sun, a distant star is an unresolved point of light, so astronomers can't directly see a sunspot cross a stellar disk. Instead, they watch for the star to dim slightly when a sunspot appears.

For this measurement to be accurate and precise, astronomers calibrate their new clock by measuring the spin periods of stars with both known ages and masses. This, in turn, allows them to apply their findings to other stars.

"We have found that the relationship between mass, rotation rate and age is now defined well enough by observations that we can obtain the ages of individual stars to within 10 percent," said Sydney Barnes, co-author of the new study.

The findings could mean a new way to determine the age of stars. This, in turn, could be huge for learning more about other solar systems and the exoplanets within them.

The findings are published in the journal Nature.

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