When Stars Collide: Evidence for a Stellar Flyby in the Solar System’s Past

Susanne Pfalzner and colleagues propose that a close stellar flyby early in the Solar System’s history explains both the orbits and colors of trans-Neptunian objects. Their simulations show that such a flyby naturally produces the observed patterns, with red TNOs remaining in low-inclination orbits and grey ones populating higher inclinations and eccentricities. Upcoming observations could test these predictions.