Magazine article Science News

Flicker Reveals Stars' Properties: Brightness Measurements Help Gauge Size and Age

Magazine article Science News

Flicker Reveals Stars' Properties: Brightness Measurements Help Gauge Size and Age

Article excerpt

The key to learning about distant stars is as simple as watching them flicker.

Stellar brightness measurements from NASA's planet-hunting Kepler space telescope can pin down once-elusive physical properties of about 170,000 stars and the planets orbiting them, scientists report in the Aug. 22 Nature. The new technique can translate modest fluctuations in starlight over several hours into insights about a star's size, surface gravity and stage of life.

"All this information is encoded in a star's brightness in such a wonderfully simple way," says astrophysicist and study coauthor Keivan Stassun of Vanderbilt University in Nashville.

For four years, the now-moribund Kepler stared at the stars within a patch of sky, looking for eclipsing planets. Kepler homed in on several hundred for meticulous scrutiny. By studying subtle changes in the brightness of these select stars, astronomers have been able to tease out vibrations in the stars' interiors--analogous to seismic waves caused by earthquakes on Earth--and precisely determine a slate of physical properties for each star, including surface gravity.

In contrast, astronomers have only rough estimates of the size, mass and other attributes of most other Kepler stars, and stars in general. "We know [the estimates] are not very good," says Ronald Gilliland, an astronomer at Penn State University in University Park, Pa.

One of the authors of the study, Fabienne Bastien, an astrophysicist at Vanderbilt, was sifting through the brightness data of the carefully studied stars when she noticed a clear-cut connection: The more a star flickered over the course of several hours, the weaker its surface gravity. …

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