Exoplanets can be hard to keep straight. The eight planets in our solar system are nothing next to the 2,300-plus possible planets astronomers have discovered circling other stars. But that mass anonymity changed in October, with a major new discovery announced in Nature. A team of exoplaneteers based at Switzerland’s Geneva Observatory spotted an exoplanet orbiting in the Alpha Centauri starsystem — our sun’s nearest celestial neighbor, and a favored destination for generations of sci-fi writers. Just four light years from Earth, Alpha Centauri could be reached, in theory, within a human lifetime—provided the right technology were invented. What’s more, the planet—dubbed Alpha Centauri Bb—is approximately the same size and perhaps the same composition as Earth. The hitch: it orbits only 3.72 million miles (6 million km) from its home star, compared to Earth, which stands at a cooler—and more life-sustaining—remove of 93 million (15 million km) from the sun.