Illustration of Habitable-Zone Exoplanet (image) NASA/Goddard Space Flight Center Share Print E-Mail Caption An illustration of Kepler-186f, the first Earth-size planet discovered within a star's habitable zone. Scientists now know of thousands of exoplanets, but our knowledge is limited because we can't yet view them directly. Credit NASA Ames/SETI Institute/JPL-Caltech Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.