PHOTOS: Top Exoplanets for Alien Life
Kepler-22b is a planet with a 95 percent probability of being in its parent star's habitable zone. Around 620 light-years away from us, it has a radius about 2.4 times as large as Earth, and is about 10 percent as massive as Jupiter. With that size, it's most likely to be a gas giant.
Unfortunately, no moon was found around Kepler-22b. If it has any moons at all, they must be smaller than half Earth's mass. Nonetheless, this was far from a wasted exercise. Planet hunters now have a small arsenal of tools and techniques at their disposal - enough for Kipping and his colleagues to draw the conclusion that if any Earth-like moon is there to be found around similar planets, they will find it.
Planet Kepler-22b was chosen for this search for several reasons. As well as being comfortably in the habitable zone and having been confirmed by Kepler observations, this planet also had radial velocity data available for it, and the observations contain very low noise (take it from me, noise in observations is the bane of an astronomer's life!).