Why are many exoplanets discovered by the transit method rather than by direct imaging?

Directly imaging an exoplanet is difficult because a star outshines its planets by an enormous amount. The transit method looks for a tiny, periodic drop in brightness when a planet passes in front of its star. NASA’s Kepler mission, launched in 2009, used this technique to find thousands of exoplanet candidates by monitoring more than 150,000 stars. The method is powerful because it can reveal a planet’s size, orbit, and sometimes even hints about its atmosphere.