It’s the stuff we’re used to seeing in movies—a mysterious large planet, sitting at the very fringes of our solar system. This time, it’s not the sci-fi spawn of Spielberg, but instead something very real. At a distance a thousand times farther from the Sun than Earth is, there waits an undiscovered world astronomers call “Planet Nine.” More than 175,000 volunteers have been combing NASA data to find this hypothetical planet.