The robot telescope settles on its target, a star that sits closer than all but a tiny fraction of the tens of billions of stellar systems that make up the Milky Way. Its mirror grabs light for 55 seconds, again and again. The robot telescope—called TRAPPIST—will observe the star for 245 hours across sixty-two nights, making 12,295 measurements. Eleven times, it will see the star dim, ever so slightly. This dip in luminosity, called a transit, has a straightforward astronomical explanation: It’s a planet passing in front of the star, blocking just a bit of its light. In this case, the transits tell us that 3 planets orbit the star.