ScienceDaily (Apr. 8, 2011) — NASA's Kepler Mission has detected changes in brightness in 500 sun-like stars, giving astronomers a much better idea about the nature and evolution of the stars.

Prior to Kepler's launch in March 2009, astronomers had identified the changes in brightness, or oscillations, of about 25 stars similar to our sun in size, age, composition and location within the Milky Way galaxy.
The discoveries are reported in a paper, "Ensemble Asteroseismology of Solar-Type Stars with the NASA Kepler Mission," in the April 8 issue of the journal Science. The lead author of the paper is Bill Chaplin of the University of Birmingham in the United Kingdom.
The paper says Kepler is a big boost to asteroseismology, the study of stars by observations of their natural oscillations. Those oscillations provide clues about star basics such as mass, radius and age as well as clues about the internal structure of stars.
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http://www.sciencedaily.com/releases/2011/04/110407141330.htm