For astronomers, a tiny blip in data can signal the existence of an entire world. It happens when a planet far beyond our solar system passes in front of its own star. The planet blocks a tiny bit of light, making the shining star appear fainter to us. Scientists have used these moments to discover thousands of exoplanets in the Milky Way—icy planets and lava planets, hot Jupiters and miniature Neptunes, planets with a thick atmosphere and planets with no atmosphere at all. A whole array of mysterious, distant worlds, all orbiting their own sun.

Which raises