01 October 2010
Vol 330, Issue 6000

About The Cover

Cover image expansion

COVER An artist?s rendition of the Kepler-9 system in which two Saturn-size planets transit the same star. The radii of the planets are roughly 8% of the radius of the star, which itself is 10% larger in radius than our Sun. Timing variations in the transits of these planets provide a signature of their gravitational interaction and can be used to establish their masses. See page 51. Image: NASA/Ames/JPL Caltech/T. Pyle