Astronomers use 'flicker' of light to probe distant stars

NASHVILLE, Aug. 21 (UPI) -- U.S. astronomers say they've found a new way to analyze flickering light from a distant star to reveal the strength of gravity at its surface.

Surface gravity is a key property that allows astronomers to calculate a star's physical properties and assess its evolutionary state, they said.

The technique was developed by a team of astronomers headed by Vanderbilt University researcher Keivan Stassun.

"Once you know a star's surface gravity then you only need one other measurement, its temperature, which is pretty easy to obtain, to determine its mass, size and other important physical properties," Stassun said.

The new method, dubbed a "flicker" process, looks at variations in the star's brightness that last 8 hours or less and appear to be linked to granulation -- the network of small cells that cover the surface of a star and are caused by columns of gas rising from the interior.

On stars with high surface gravity, the researchers found, the granulation is finer and flickers at a higher frequency, while on stars with low surface gravity, the granulation is coarser and they flicker at a lower frequency.

"Measuring stellar surface gravities well has always been a difficult business," study contributor Gibor Basri of the University of California, Berkeley, said. "So it is a very pleasant surprise to find that the subtle flickering of a star's light provides a relatively easy way to do it."