2004 XR190

2004 XR₁₉₀ is a possible dwarf planet located in the scattered disc. It has a highly inclined low-eccentricity orbit. It was discovered in December 2004.

History

Discovery

2004 XR₁₉₀ was discovered on 11 December 2004. It was discovered by astronomers led by Lynne Jones of the University of British Columbia as part of the Canada–France Ecliptic Plane Survey (CFEPS) using the Canada–France–Hawaii Telescope (CFHT) near the ecliptic. In 2015, six precovery images from 2002 and 2003 were found in Sloan Digital Sky Survey data.

Naming

The discovery team nicknamed 2004 XR₁₉₀ "Buffy", after the fictional vampire slayer, and proposed several Inuit-based official names to the IAU.

Orbit

Considered a detached object,2004 XR₁₉₀ is particularly unusual for two reasons. With an inclination of 47 degrees, it is the largest possible dwarf planet that has an inclination larger than 45 degrees, traveling further "up and down" than "left to right" around the Sun when viewed edge-on along the ecliptic. Second, it has an unusually circular orbit for a scattered-disc object (SDO). Although it is thought that traditional scattered-disc objects have been ejected into their current orbits by gravitational interactions with Neptune, the low eccentricity of its orbit and the distance of its perihelion (SDOs generally have highly eccentric orbits and perihelia less than 38 AU) seems hard to reconcile with such celestial mechanics. This has led to some uncertainty as to the current theoretical understanding of the outer Solar System. The theories include close stellar passages, rogue planets/planetary embryos in the early Kuiper belt, and resonance interaction with an outward-migrating Neptune. The Kozai mechanism is capable of transferring orbital eccentricity to a higher inclination.