A large, undiscovered planet lurking on the fringe of the solar system is a compelling idea—and it’s nothing new. It’s been proposed many times. And those predictions have always been wrong.

So what about this latest prediction, the one that might actually be right?

(In case you missed it, a new study from Caltech suggests there might be a large world way out there—a planet whose gravitational hand is sculpting the orbits of distant, icy worlds and forcing them to take weird paths around the sun.)

How can we figure out if the planet is actually there? And will it even be bright enough to see? Here are some answers to these and other pressing questions.

No. The evidence is tantalizing, but it’s circumstantial. UCSC astronomer Greg Laughlin gives the