NASA's Kepler Discovers First Earth-Size Planet In The 'Habitable Zone' of Another Star Editor's note: On July 23, 2015, NASA's Kepler mission confirmed the first near-Earth-size planet in the “habitable zone” around a sun very similar to our star. For more information about this latest discovery, visit: NASA’s Kepler Mission Discovers Bigger, Older Cousin to Earth. kepler186f_artistconcept.jpg The artist's concept depicts Kepler-186f , the first validated Earth-size planet to orbit a distant star in the habitable zone Credits: NASA Ames/SETI Institute/JPL-Caltech Full Image