Planet Search

Math helps us chart the universe.

- Ivars Peterson

On a clear night, away from city lights, you can see a sky packed with stars. But you can’t see planets orbiting any of these stars, even with the strongest Earth-based telescopes. Planets are smaller than stars and don’t give off heir own light to make them visible.

Astronomers reported the discovery of seven Earth-sized planets orbiting a nearby star called TRAPPIST-1 in February 2017. They had to rely on indirect evidence to tell them that the planets are there. By doing some math, they figured out the number of planets and the distance of their orbits.