Planet Occurrence Rates

This is an excerpt from my post on Planet Hunters:

Planet Hunters will soon start work on a new, important question in the field of exoplanets: how common are planets around other stars? This question has become a hot topic in exoplanets, but Planet Hunters has one major, unique advantage. Planet Hunters are sensitive to planets with just one or two transits. The automated computer algorithms require three or more transits; otherwise, they would be overloaded with spurious signals. This allows Planet Hunters to explore much longer periods than the rest of the field.

Until now, Planet Hunters have been looking for planets one quarter at a time. This has been successful in discovering more than 60 new planet candidates and two new confirmed planets (and counting). However, this one-quarter-at-a-time method doesn’t let us figure out how common planets truly are.