More and more astronomers have joined the hunt, discovering smaller and smaller planets.
But the apparent profusion of such stars has encouraged astronomers to think that smaller planets may be abundant as well.
These systems, due to complications from Earth's atmosphere, cannot see the older, smaller planets that are similar to Earth.
Transit detection can pick up much smaller planets than previous methods based on gravity-induced wobbles in the stellar parent.
Asked if he was surprised to find Saturn-size planets, Dr. Butler responded, "I would have been more shocked if we hadn't found smaller and smaller planets".
If cloud cover were widespread on smaller planets beyond the solar system, astronomers would need radically different approaches or far more advanced technology to probe their atmospheres.
Most of their orbits, he said, are wildly eccentric, which would abet destructive chaos among smaller planets rather than shielding them.
"As we develop the technique further we will be able to study wind flows in increasing detail and make weather maps of smaller planets".
A vast majority of them are Jupiter-size giants, but as techniques have improved, astronomers have been able to detect smaller and smaller planets.
Astronomers will soon be able to identify smaller planets farther out, including truly Earth-size planets in orbits that would impart Earth-like temperatures.
As techniques are developed for detecting smaller planets, astronomers will gain a better understanding of how planetary systems, including the Sun's, form and evolve.
