Two months after the <a href="http://www.uproxx.com/gammasquad/2011/12/first-exoplanet-in-the-habitable-zone-of-a-sun-like-star-discovered-kepler-22b">first discovery</a> of an exoplanet orbiting in the habitable zone of a sun-like star and one month after the <a href="http://www.uproxx.com/gammasquad/2011/12/smallest-exoplanets-orbiting-a-sun-like-star-discovered">first discovery</a> of the two exoplanets similar in size to Earth (Kepler-20e and Kepler-20f, pictured above), researchers using the Keck Observatory in Hawaii and public data from NASA's Kepler mission have discovered the smallest exoplanets yet.