NASA's Kepler probe is designed to find Earth-sized planets around other stars. Now, scientists have determined it will also be possible to find "exo-moons"-- moons orbiting exo-planets.
As Kepler will detect planets by noting dips in the light from a star as a planet passes between Kepler and the star it will also be possible to detect wobbling in the planet's movement that would be due to the pull of a moon's gravity on the planet.
The best kind of planet for such a moon search would be one similar to Saturn-- large, but not very dense-- that a moon's gravity could move around. That brings up an interesting possiblity. A Saturn-like planet orbiting in the habitable zone of a star might not be a good candidate to harbor life, but a substantial enough moon of that planet could be.