How do astronomers detect planets around other stars?

The transit method detects a planet when it blocks a small fraction of its star’s light during an orbit, causing a repeating dip in brightness. The radial velocity method measures how a star moves toward and away from Earth under the planet’s gravitational pull. NASA’s Kepler mission, launched in 2009, revolutionized the search for transiting exoplanets, while later missions like TESS expanded the hunt. Together, these methods have shown that planets are common throughout the Milky Way.