It was almost 100 years ago that Clyde W. Tombaugh discovered Pluto. That was the last planet found until 1992, when humans found another one. But this new planet wasn’t in our solar system—it was orbiting another star. We call this an extrasolar planet, or “exoplanet” for short.
Since then, astronomers have cataloged more than 6,000 exoplanets. If you thought it was hard to remember the names of our own planets, try all the planets, with names like HD 189733b. (A jolly place where it rains molten glass and the wind blows 9,000 kilometers per hour.)
Even the closest exoplanets are more than 4 light years away (36 trillion miles), which