NASA, Looking for the Shadows of New Worlds

Astronomers have used many different methods to discover planets beyond the solar system, but the most successful by far is transit photometry, which measures changes in a star s brightness caused by a minieclipse. When a planet crosses in front of its star along our line of sight, it blocks some of the star s light. If the dimming lasts for a set amount of time and occurs at regular intervals, it likely means an exoplanet is passing in front of, or transiting, the star once every orbital period. NASAs