By Ron Cowen
Using sensitive light detectors to record a cosmic orchestra — sound waves emanating from thousands of distant stars — NASA’s Kepler spacecraft is hitting the high notes, the low notes and everything in between. The amplitude and frequency of each sound wave, which Kepler detects as tiny flickers in starlight, has already enabled the craft to pin down the age and size of a sunlike star to unprecedented accuracy, researchers said October 26 during a telephone briefing with reporters. Along with data gathered by a European mission, COROT, the Kepler observations could lead to new insights about stars that harbor planets, researchers noted.
“The determination of masses, radii and ages of planet-hosting stars is of paramount relevance as these parameters can be used to characterize the planet itself — for instance its mean density, which gives insight into its internal structure and composition,” said Andrea Miglio of the University of Liège in Belgium.
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Although the sunlike KIC 11026764, described during the briefing, isn’t known to harbor planets, it demonstrates that researchers can use Kepler to precisely determine the diameter and age of stars that do host planets, said Travis Metcalfe of the National Center for Atmospheric Research in Boulder, Colo. That information can in turn advance Kepler’s main mission of finding planets as small as Earth by detecting the tiny amount of light they block each time they pass in front of their parent stars.
The amount of light blocked during each minieclipse and its duration depends on the relative diameters of the parent star and the planet. By measuring the star’s diameter, researchers can then determine the diameter of the orbiting planet and more importantly, accurately calculate the planet’s density — an indication of the planet’s composition and, perhaps, its potential for habitability.