The 10 Mya High-Chord Flyby: A Transient Gravitational Alternative to the Planet 9 Hypothesis

This paper challenges the prevailing "Planet 9" hypothesis—which requires a permanent ~5–10 M⊕ (Earth mass) planet—by proposing a Transient High-Chord Flyby model. We hypothesize that a rogue planet of approximately 5 M⊕ passed through a high-latitude chord of the Oort Cloud approximately 10 million years ago (Mya). This encounter provided a singular gravitational impulse that accounts for the observed orbital clustering of extreme trans-Neptunian objects (ETNOs) and the existence of "detached" objects like Sedna.