This image provided by NASA shows an artist rendering of the newfound 

This image provided by NASA shows an artist rendering of the newfound planet known as Kepler-37b. The planet is about the size of our moon and is the smallest known exoplanet, according to a study published in Thursday Feb. 21,2013 issue of the journal Nature. (AP Photo/NASA/Ames/JPL-Caltech)
Associated Press
This image provided by NASA shows an artist rendering of the newfound planet known as Kepler-37b. The planet is about the size of our moon and is the smallest known exoplanet, according to a study published in Thursday Feb. 21,2013 issue of the journal Nature. (AP Photo/NASA/Ames/JPL-Caltech)
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