DISCOVERY OF A NEW RETROGRADE TRANS-NEPTUNIAN OBJECT: HINT OF A COMMON ORBITAL PLANE FOR LOW SEMIMAJOR AXIS, HIGH-INCLINATION TNOs AND CENTAURS

ABSTRACT Although the majority of Centaurs are thought to have originated in the scattered disk, with the high-inclination members coming from the Oort cloud, the origin of the high-inclination component of trans-Neptunian objects (TNOs) remains uncertain. We report the discovery of a retrograde TNO, which we nickname “Niku,” detected by the Pan-STARRS 1 Outer Solar System Survey. Our numerical integrations show that the orbital dynamics of Niku are very similar to that of 2008 KV 42 (Drac), with a half-life of ∼500 Myr. Comparing similar high-inclination TNOs and Centaurs ( q > 10 au, a < 100 au, and i > 60°), we find that these objects exhibit a surprising clustering of ascending node, and occupy a common orbital plane. This orbital configuration has high statistical significance: 3.8- σ . An unknown mechanism is required to explain the observed clustering. This discovery may provide a pathway to investigating a possible reservoir of high-inclination objects.