The inner lives of red giants

Abstract

The natural pulse of a red-giant star provides crucial insight into what makes it shine. Observations of red giants by the Kepler space telescope shed light on a previously untested prediction of stellar evolution theory. See Letter p.608 NASA's Kepler mission has been remarkably productive in its primary role, that of discovering and characterizing extrasolar planets. It does this indirectly, by monitoring the brightness of many thousands of main sequence stars in search of periodic fluctuations caused by planets crossing the face of the stars. But the high-precision photometry involved is also ideal for studying the stars themselves. Bedding et al. have used Kepler data to probe the internal structure of red giants. Their detailed measurements of the gravity modes in the cores of these stars allow them to distinguish between those burning hydrogen in a shell around a relatively inactive core and those burning helium in the core.