An Ancient Stellar Flyby Could Have Put Planet Nine into its Distant Orbit

New observations of a distant exoplanet and its solar system offer proof of a long-standing astronomical theory: passing stars can perturb planetary systems and change planets’ orbits – for better or worse. Depending on how they pass by, stars can nudge planets into more stable orbits or give them a kick that sends out of the system entirely. And new evidence implies that these kinds of encounters may explain the paths of strange objects in our own solar system, l