Way, way out at the cold, dark edges of the solar system—past the rocky inner planets, beyond the gas giants, a billion miles more remote than Pluto—drifts a tiny frozen world so mysterious, scientists still aren't entirely sure if it's one world or two. Astronomers call it Ultima Thule, an old cartography term meaning "beyond the known world.
Learn about your ad choices:
dovetail.prx.org/ad-choices
