If the solar system does have a Planet Nine, it is a world that was bullied by its larger siblings, exiled to the far reaches of space and only rescued from oblivion thanks to the intervention of passing stars.

Planet Nine is a hypothesised planet that is five to 10 times the mass of Earth, orbiting in the outer solar system at about 400 to 800 times the Earth-sun distance. The best evidence for its existence comes from a clustering of objects orbiting far from the sun,…